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NAME | OVERVIEW OF THE ABIGAIL FRAMEWORK | TOOLS | CONCEPTS | AUTHOR | COPYRIGHT | COLOPHON |
LIBABIGAIL(7) Libabigail LIBABIGAIL(7)
libabigail - Library to analyze and compare ELF ABIs
ABIGAIL stands for the Application Binary Interface Generic Analysis
and Instrumentation Library.
It's a framework which aims at helping developers and software
distributors to spot some ABI-related issues like interface
incompatibility in ELF shared libraries by performing a static
analysis of the ELF binaries at hand.
The type of interface incompatibilities that Abigail focuses on is
related to changes on the exported ELF functions and variables
symbols, as well as layout and size changes of data types of the
functions and variables exported by shared libraries.
In other words, if the return type of a function exported by a shared
library changes in an incompatible way from one version of a given
shared library to another, we want Abigail to help people catch that.
In more concrete terms, the Abigail framwork provides a shared
library named libabigail which exposes an API to parse a shared
library in ELF format (accompanied with its associated debug
information in DWARF format) build an internal representation of all
the functions and variables it exports, along with their types.
Libabigail also builds an internal representation of the ELF symbols
of these functions and variables. That information about these
exported functions and variables is roughly what we consider as being
the ABI of the shared library, at least, in the scope of Libabigail.
Aside of this internal representation, libabigail provides facilities
to perform deep comparisons of two ABIs. That is, it can compare the
types of two sets of functions or variables and represents the result
in a way that allows it to emit textual reports about the
differences.
This allows us to write tools like abidiff that can compare the ABI
of two shared libraries and represent the result in a meaningful
enough way to help us spot ABI incompatibilities. There are several
other tools that are built using the Abigail framwork.
Overview
The upstream code repository of Libabigail contains several tools
written using the library. They are maintained and released as part
of the project. All tools come with a bash-completion script.
Tools manuals
abidiff
abidiff compares the Application Binary Interfaces (ABI) of two
shared libraries in ELF format. It emits a meaningful report
describing the differences between the two ABIs.
This tool can also compare the textual representations of the ABI of
two ELF binaries (as emitted by abidw) or an ELF binary against a
textual representation of another ELF binary.
For a comprehensive ABI change report that includes changes about
function and variable sub-types, the two input shared libraries must
be accompanied with their debug information in DWARF format.
Otherwise, only ELF symbols that were added or removed are reported.
Invocation
abidiff [options] <first-shared-library> <second-shared-library>
Environment
abidiff loads two default suppression specifications files, merges
their content and use it to filter out ABI change reports that might
be considered as false positives to users.
· Default system-wide suppression specification file
It's located by the optional environment variable
LIBABIGAIL_DEFAULT_SYSTEM_SUPPRESSION_FILE. If that environment
variable is not set, then abidiff tries to load the suppression
file $libdir/libabigail/libabigail-default.abignore. If that file
is not present, then no default system-wide suppression
specification file is loaded.
· Default user suppression specification file.
It's located by the optional environment
LIBABIGAIL_DEFAULT_USER_SUPPRESSION_FILE. If that environment
variable is not set, then abidiff tries to load the suppression
file $HOME/.abignore. If that file is not present, then no default
user suppression specification is loaded.
Options
· --help | -h
Display a short help about the command and exit.
· --version | -v
Display the version of the program and exit.
· --debug-info-dir1 | --d1 <di-path1>
For cases where the debug information for first-shared-library
is split out into a separate file, tells abidiff where to find
that separate debug information file.
Note that di-path must point to the root directory under which
the debug information is arranged in a tree-like manner. Under
Red Hat based systems, that directory is usually
<root>/usr/lib/debug.
Note also that this option is not mandatory for split debug
information installed by your system's package manager because
then abidiff knows where to find it.
· --debug-info-dir2 | --d2 <di-path2>
Like --debug-info-dir1, this options tells abidiff where to find
the split debug information for the second-shared-library file.
· --headers-dir1 | --hd1 <headers-directory-path-1>
Specifies where to find the public headers of the first shared
library that the tool has to consider. The tool will thus
filter out ABI changes on types that are not defined in public
headers.
· --headers-dir2 | --hd2 <headers-directory-path-1>
Specifies where to find the public headers of the second shared
library that the tool has to consider. The tool will thus
filter out ABI changes on types that are not defined in public
headers.
· --no-linux-kernel-mode
Without this option, if abidiff detects that the binaries it is
looking at are Linux Kernel binaries (either vmlinux or modules)
then it only considers functions and variables which ELF symbols
are listed in the __ksymtab and __ksymtab_gpl sections.
With this option, abidiff considers the binary as a non-special
ELF binary. It thus considers functions and variables which are
defined and exported in the ELF sense.
· --kmi-whitelist | -kaw <path-to-whitelist>
When analyzing a Linux kernel binary, this option points to the
white list of names of ELF symbols of functions and variables
which ABI must be considered. That white list is called a
"Kernel Module Interface white list". This is because for the
Kernel, we don't talk about ABI; we rather talk about the
interface between the Kernel and its module. Hence the term KMI
rather than ABI.
Any other function or variable which ELF symbol are not present
in that white list will not be considered by this tool.
If this option is not provided -- thus if no white list is
provided -- then the entire KMI, that is, the set of all
publicly defined and exported functions and global variables by
the Linux Kernel binaries, is considered.
· --drop-private-types
This option is to be used with the --headers-dir1 and
--headers-dir2 options. With this option, types that are NOT
defined in the headers are entirely dropped from the internal
representation build by Libabigail to represent the ABI. They
thus don't have to be filtered out from the final ABI change
report because they are not even present in Libabigail's
representation.
Without this option however, those private types are kept in the
internal representation and later filtered out from the report.
This options thus potentially makes Libabigail consume less
memory. It's meant to be mainly used to optimize the memory
consumption of the tool on binaries with a lot of publicly
defined and exported types.
· --stat
Rather than displaying the detailed ABI differences between
first-shared-library and second-shared-library, just display
some summary statistics about these differences.
· --symtabs
Only display the symbol tables of the first-shared-library and
second-shared-library.
· --deleted-fns
In the resulting report about the differences between
first-shared-library and second-shared-library, only display the
globally defined functions that got deleted from
first-shared-library.
· --changed-fns
In the resulting report about the differences between
first-shared-library and second-shared-library, only display the
changes in sub-types of the global functions defined in
first-shared-library.
· --added-fns
In the resulting report about the differences between
first-shared-library and second-shared-library, only display the
globally defined functions that were added to
second-shared-library.
· --deleted-vars
In the resulting report about the differences between
first-shared-library and second-shared-library, only display the
globally defined variables that were deleted from
first-shared-library.
· --changed-vars
In the resulting report about the differences between
first-shared-library and second-shared-library, only display the
changes in the sub-types of the global variables defined in
first-shared-library
· --added-vars
In the resulting report about the differences between
first-shared-library and second-shared-library, only display the
global variables that were added (defined) to
second-shared-library.
· --no-added-syms
In the resulting report about the differences between
first-shared-library and second-shared-library, do not display
added functions or variables. Do not display added functions or
variables ELF symbols either. All other kinds of changes are
displayed unless they are explicitely forbidden by other options
on the command line.
· --no-linkage-name
In the resulting report, do not display the linkage names of the
added, removed, or changed functions or variables.
· --no-show-locs
Do not show information about where in the second shared
library the respective type was changed.
· --no-show-relative-offset-changes
Without this option, when the offset of a data member changes,
the change report not only mentions the older and newer offset,
but it also mentions by how many bits the data member changes.
With this option, the latter is not shown.
· --no-unreferenced-symbols
In the resulting report, do not display change information about
function and variable symbols that are not referenced by any
debug information. Note that for these symbols not referenced
by any debug information, the change information displayed is
either added or removed symbols.
· --no-default-suppression
Do not load the default suppression specification files.
· --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at
path-to-suppressions. Note that this option can appear multiple
times on the command line. In that case, all of the provided
suppression specification files are taken into account.
Please note that, by default, if this option is not provided,
then the default suppression specification files are loaded .
· --drop <regex>
When reading the first-shared-library and second-shared-library
ELF input files, drop the globally defined functions and
variables which name match the regular expression regex. As a
result, no change involving these functions or variables will be
emitted in the diff report.
· --drop-fn <regex>
When reading the first-shared-library and second-shared-library
ELF input files, drop the globally defined functions which name
match the regular expression regex. As a result, no change
involving these functions will be emitted in the diff report.
· --drop-var <regex>
When reading the first-shared-library and second-shared-library
ELF input files, drop the globally defined variables matching a
the regular expression regex.
· --keep <regex>
When reading the first-shared-library and second-shared-library
ELF input files, keep the globally defined functions and
variables which names match the regular expression regex. All
other functions and variables are dropped on the floor and will
thus not appear in the resulting diff report.
· --keep-fn <regex>
When reading the first-shared-library and second-shared-library
ELF input files, keep the globally defined functions which name
match the regular expression regex. All other functions are
dropped on the floor and will thus not appear in the resulting
diff report.
· --keep-var <regex>
When reading the first-shared-library and second-shared-library
ELF input files, keep the globally defined which names match the
regular expression regex. All other variables are dropped on
the floor and will thus not appear in the resulting diff report.
· --harmless
In the diff report, display only the harmless changes. By
default, the harmless changes are filtered out of the diff
report keep the clutter to a minimum and have a greater chance
to spot real ABI issues.
· --no-harmful
In the diff report, do not display the harmful changes. By
default, only the harmful changes are displayed in diff report.
· --redundant
In the diff report, do display redundant changes. A redundant
change is a change that has been displayed elsewhere in the
report.
· --no-redundant
In the diff report, do NOT display redundant changes. A
redundant change is a change that has been displayed elsewhere
in the report. This option is switched on by default.
· --no-architecture
Do not take architecture in account when comparing ABIs.
· --no-corpus-path
Do not emit the path attribute for the ABI corpus.
· --dump-diff-tree
After the diff report, emit a textual representation of the
diff nodes tree used by the comparison engine to represent the
changed functions and variables. That representation is
emitted to the error output for debugging purposes. Note that
this diff tree is relevant only to functions and variables
that have some sub-type changes. Added or removed functions
and variables do not have any diff nodes tree associated to
them.
· --stats
Emit statistics about various internal things.
· --verbose
Emit verbose logs about the progress of miscellaneous internal
things.
Return values
The exit code of the abidiff command is either 0 if the ABI of the
binaries being compared are equal, or non-zero if they differ or if
the tool encountered an error.
In the later case, the exit code is a 8-bits-wide bit field in which
each bit has a specific meaning.
The first bit, of value 1, named ABIDIFF_ERROR means there was an
error.
The second bit, of value 2, named ABIDIFF_USAGE_ERROR means there was
an error in the way the user invoked the tool. It might be set, for
instance, if the user invoked the tool with an unknown command line
switch, with a wrong number or argument, etc. If this bit is set,
then the ABIDIFF_ERROR bit must be set as well.
The third bit, of value 4, named ABIDIFF_ABI_CHANGE means the ABI of
the binaries being compared are different.
The fourth bit, of value 8, named ABIDIFF_ABI_INCOMPATIBLE_CHANGE
means the ABI of the binaries compared are different in an
incompatible way. If this bit is set, then the ABIDIFF_ABI_CHANGE
bit must be set as well. If the ABIDIFF_ABI_CHANGE is set and the
ABIDIFF_INCOMPATIBLE_CHANGE is NOT set, then it means that the ABIs
being compared might or might not be compatible. In that case, a
human being needs to review the ABI changes to decide if they are
compatible or not.
Note that, at the moment, there are only a few kinds of ABI changes
that would result in setting the flag
ABIDIFF_ABI_INCOMPATIBLE_CHANGE. Those ABI changes are either:
· the removal of the symbol of a function or variable that has
been defined and exported.
· the modification of the index of a member of a virtual function
table (for C++ programs and libraries).
With time, when more ABI change patterns are found to always
constitute incompatible ABI changes, we will adapt the code to
recognize those cases and set the ABIDIFF_ABI_INCOMPATIBLE_CHANGE
accordingly. So, if you find such patterns, please let us know.
The remaining bits are not used for the moment.
Usage examples
1. Detecting a change in a sub-type of a function:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0* /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct type_base
5 {
6 int inserted;
7 };
8
9 struct S0 : public type_base
10 {
11 int m0;
12 };
13
14 void
15 foo(S0* /*parameter_name*/)
16 {
17 // do something with parameter_name.
18 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void foo(S0*)' has some indirect sub-type changes:
parameter 0 of type 'S0*' has sub-type changes:
in pointed to type 'struct S0':
size changed from 32 to 64 bits
1 base class insertion:
struct type_base
1 data member change:
'int S0::m0' offset changed from 0 to 32
$
2. Detecting another change in a sub-type of a function:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0& /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct S0
5 {
6 char inserted_member;
7 int m0;
8 };
9
10 void
11 foo(S0& /*parameter_name*/)
12 {
13 // do something with parameter_name.
14 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void foo(S0&)' has some indirect sub-type changes:
parameter 0 of type 'S0&' has sub-type changes:
in referenced type 'struct S0':
size changed from 32 to 64 bits
1 data member insertion:
'char S0::inserted_member', at offset 0 (in bits)
1 data member change:
'int S0::m0' offset changed from 0 to 32
$
3. Detecting that functions got removed or added to a library:
$ cat -n test-v0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
3
4 struct S0
5 {
6 int m0;
7 };
8
9 void
10 foo(S0& /*parameter_name*/)
11 {
12 // do something with parameter_name.
13 }
$
$ cat -n test-v1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
3
4 struct S0
5 {
6 char inserted_member;
7 int m0;
8 };
9
10 void
11 bar(S0& /*parameter_name*/)
12 {
13 // do something with parameter_name.
14 }
$
$ g++ -g -Wall -shared -o libtest-v0.so test-v0.cc
$ g++ -g -Wall -shared -o libtest-v1.so test-v1.cc
$
$ ../build/tools/abidiff libtest-v0.so libtest-v1.so
Functions changes summary: 1 Removed, 0 Changed, 1 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 Removed function:
'function void foo(S0&)' {_Z3fooR2S0}
1 Added function:
'function void bar(S0&)' {_Z3barR2S0}
$
abipkgdiff
abipkgdiff compares the Application Binary Interfaces (ABI) of the
ELF binaries contained in two software packages. The software
package formats currently supported are Deb, RPM, tar archives
(either compressed or not) and plain directories that contain
binaries.
For a comprehensive ABI change report that includes changes about
function and variable sub-types, the two input packages must be
accompanied with their debug information packages that contain debug
information in DWARF format.
Invocation
abipkgdiff [option] <package1> <package2>
package1 and package2 are the packages that contain the binaries to
be compared.
Environment
abipkgdiff loads two default suppression specifications files, merges
their content and use it to filter out ABI change reports that might
be considered as false positives to users.
· Default system-wide suppression specification file
It's located by the optional environment variable
LIBABIGAIL_DEFAULT_SYSTEM_SUPPRESSION_FILE. If that environment
variable is not set, then abipkgdiff tries to load the suppression
file $libdir/libabigail/libabigail-default.abignore. If that file
is not present, then no default system-wide suppression
specification file is loaded.
· Default user suppression specification file.
It's located by the optional environment
LIBABIGAIL_DEFAULT_USER_SUPPRESSION_FILE. If that environment
variable is not set, then abipkgdiff tries to load the suppression
file $HOME/.abignore. If that file is not present, then no default
user suppression specification is loaded.
Options
· --help | -h
Display a short help about the command and exit.
· --version | -v
Display the version of the program and exit.
· --debug-info-pkg1 | --d1 <path>
For cases where the debug information for package1 is split out
into a separate file, tells abipkgdiff where to find that
separate debug information package.
· --debug-info-pkg2 | --d2 <path>
For cases where the debug information for package2 is split out
into a separate file, tells abipkgdiff where to find that
separate debug information package.
· --devel-pkg1 | --devel1 <path>
Specifies where to find the Development Package associated with
the first package to be compared. That Development Package at
path should at least contain header files in which public types
exposed by the libraries (of the first package to be compared)
are defined. When this option is provided, the tool filters out
reports about ABI changes to types that are NOT defined in these
header files.
· --devel-pkg2 | --devel2 <path>
Specifies where to find the Development Package associated with
the second package to be compared. That Development Package at
path should at least contains header files in which public types
exposed by the libraries (of the second package to be compared)
are defined. When this option is provided, the tool filters out
reports about ABI changes to types that are NOT defined in these
header files.
· --drop-private-types
This option is to be used with the --devel-pkg1 and --devel-pkg2
options. With this option, types that are NOT defined in the
headers are entirely dropped from the internal representation
build by Libabigail to represent the ABI. They thus don't have
to be filtered out from the final ABI change report because they
are not even present in Libabigail's representation.
Without this option however, those private types are kept in the
internal representation and later filtered out from the report.
This options thus potentially makes Libabigail consume less
memory. It's meant to be mainly used to optimize the memory
consumption of the tool on binaries with a lot of publicly
defined and exported types.
· --dso-only
Compare ELF files that are shared libraries, only. Do not
compare executable files, for instance.
· --redundant
In the diff reports, do display redundant changes. A
redundant change is a change that has been displayed elsewhere
in a given report.
· --harmless
In the diff report, display only the harmless changes. By
default, the harmless changes are filtered out of the diff
report keep the clutter to a minimum and have a greater chance
to spot real ABI issues.
· --no-linkage-name
In the resulting report, do not display the linkage names of the
added, removed, or changed functions or variables.
· --no-added-syms
Do not show the list of functions, variables, or any symbol that
was added.
· --no-added-binaries
Do not show the list of binaries that got added to the second
package.
Please note that the presence of such added binaries is not
considered like an ABI change by this tool; as such, it doesn't
have any impact on the exit code of the tool. It does only have
an informational value. Removed binaries are, however,
considered as an ABI change.
· --no-abignore
Do not search the package2 for the presence of suppression
files.
· --no-parallel
By default, abipkgdiff will use all the processors it has
available to execute concurrently. This option tells it not to
extract packages or run comparisons in parallel.
· --no-default-suppression
Do not load the default suppression specification files.
· --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at
path-to-suppressions. Note that this option can appear multiple
times on the command line. In that case, all of the suppression
specification files are taken into account.
Please note that, by default, if this option is not provided,
then the default suppression specification files are loaded .
· --linux-kernel-abi-whitelist | --lkaw <path-to-whitelist>
When comparing two Linux kernel RPM packages, this option points
to the white list of names of ELF symbols of functions and
variables that must be compared for ABI changes. That white
list is called a "Linux kernel ABI white list".
Any other function or variable which ELF symbol are not present
in that white list will not be considered by the ABI comparison
process.
If this option is not provided -- thus if no white list is
provided -- then the ABI of all publicly defined and exported
functions and global variables by the Linux Kernel binaries are
compared.
· --lkaw-pkg <path-to-whitelist-package>
When comparing two Linux kernel RPM packages, this option points
an RPM package containining several white lists of names of ELF
symbols of functions and variables that must be compared for ABI
changes. Those white lists are called "Linux kernel ABI white
lists".
From the content of that white list package, this program then
chooses the appropriate Linux kernel ABI white list to consider
when comparing the ABI of Linux kernel binaries contained in the
Linux kernel packages provided on the command line.
That choosen Linux kernel ABI white list contains the list of
names of ELF symbols of functions and variables that must be
compared for ABI changes.
Any other function or variable which ELF symbol are not present
in that white list will not be considered by the ABI comparison
process.
If this option is not provided -- thus if no white list is
provided -- then the ABI of all publicly defined and exported
functions and global variables by the Linux Kernel binaries are
compared.
· --no-unreferenced-symbols
In the resulting report, do not display change information about
function and variable symbols that are not referenced by any
debug information. Note that for these symbols not referenced
by any debug information, the change information displayed is
either added or removed symbols.
· --no-show-locs
Do not show information about where in the second shared
library the respective type was changed.
· --no-show-relative-offset-changes
Without this option, when the offset of a data member changes,
the change report not only mentions the older and newer offset,
but it also mentions by how many bits the data member changes.
With this option, the latter is not shown.
· --show-identical-binaries
Show the names of the all binaries compared, including the
binaries whose ABI compare equal. By default, when this
option is not provided, only binaries with ABI changes are
mentionned in the output.
· --fail-no-dbg
Make the program fail and return a non-zero exit code if
couldn't read any of the debug information that comes from the
debug info packages that were given on the command line. If no
debug info package were provided on the command line then this
option is not active.
Note that the non-zero exit code returned by the program as a
result of this option is the constant ABIDIFF_ERROR. To know
the numerical value of that constant, please refer to the exit
code documentation.
· --keep-tmp-files
Do not erase the temporary directory files that are created
during the execution of the tool.
· --verbose
Emit verbose progress messages.
Return value
The exit code of the abipkgdiff command is either 0 if the ABI of the
binaries compared are equal, or non-zero if they differ or if the
tool encountered an error.
In the later case, the value of the exit code is the same as for the
abidiff tool.
abicompat
abicompat checks that an application that links against a given
shared library is still ABI compatible with a subsequent version of
that library. If the new version of the library introduces an ABI
incompatibility, then abicompat hints the user at what exactly that
incompatibility is.
Invocation
abicompat [options] [<application> <shared-library-first-version> <shared-library-second-version>]
Options
· --help
Display a short help about the command and exit.
· --version | -v
Display the version of the program and exit.
· --list-undefined-symbols | -u
Display the list of undefined symbols of the application and
exit.
· --show-base-names | -b
In the resulting report emitted by the tool, this option makes
the application and libraries be referred to by their base names
only; not by a full absolute name. This can be useful for use
in scripts that wants to compare names of the application and
libraries independently of what their directory names are.
· --app-debug-info-dir | --appd <path-to-app-debug-info-directory>
Set the path to the directory under which the debug information
of the application is supposed to be laid out. This is useful
for application binaries for which the debug info is in a
separate set of files.
· --lib-debug-info-dir1 | --libd1 <path-to-lib1-debug-info>
Set the path to the directory under which the debug information
of the first version of the shared library is supposed to be
laid out. This is useful for shared library binaries for which
the debug info is in a separate set of files.
· --lib-debug-info-dir2 | --libd2 <path-to-lib1-debug-info>
Set the path to the directory under which the debug information
of the second version of the shared library is supposed to be
laid out. This is useful for shared library binaries for which
the debug info is in a separate set of files.
· --suppressions | --suppr <path-to-suppressions>
Use a suppression specification file located at
path-to-suppressions. Note that this option can appear multiple
times on the command line; all the suppression specification
files are then taken into account.
· --no-show-locs
Do not show information about where in the second shared
library the respective type was changed.
· --weak-mode
This triggers the weak mode of abicompat. In this mode, only
one version of the library is required. That is, abicompat is
invoked like this:
abicompat --weak-mode <the-application> <the-library>
Note that the --weak-mode option can even be omitted if only one
version of the library is given, along with the application; in
that case, abicompat automatically switches to operate in weak
mode:
abicompat <the-application> <the-library>
In this weak mode, the types of functions and variables exported
by the library and consumed by the application (as in, the
symbols of the these functions and variables are undefined in
the application and are defined and exported by the library) are
compared to the version of these types as expected by the
application. And if these two versions of types are different,
abicompat tells the user what the differences are.
In other words, in this mode, abicompat checks that the types of
the functions and variables exported by the library mean the
same thing as what the application expects, as far as the ABI is
concerned.
Note that in this mode, abicompat doesn't detect exported
functions or variables (symbols) that are expected by the
application but that are removed from the library. That is why
it is called weak mode.
Return values
The exit code of the abicompat command is either 0 if the ABI of the
binaries being compared are equal, or non-zero if they differ or if
the tool encountered an error.
In the later case, the exit code is a 8-bits-wide bit field in which
each bit has a specific meaning.
The first bit, of value 1, named ABIDIFF_ERROR means there was an
error.
The second bit, of value 2, named ABIDIFF_USAGE_ERROR means there was
an error in the way the user invoked the tool. It might be set, for
instance, if the user invoked the tool with an unknown command line
switch, with a wrong number or argument, etc. If this bit is set,
then the ABIDIFF_ERROR bit must be set as well.
The third bit, of value 4, named ABIDIFF_ABI_CHANGE means the ABI of
the binaries being compared are different.
The fourth bit, of value 8, named ABIDIFF_ABI_INCOMPATIBLE_CHANGE
means the ABI of the binaries compared are different in an
incompatible way. If this bit is set, then the ABIDIFF_ABI_CHANGE
bit must be set as well. If the ABIDIFF_ABI_CHANGE is set and the
ABIDIFF_INCOMPATIBLE_CHANGE is NOT set, then it means that the ABIs
being compared might or might not be compatible. In that case, a
human being needs to review the ABI changes to decide if they are
compatible or not.
The remaining bits are not used for the moment.
Usage examples
· Detecting a possible ABI incompatibility in a new shared library
version:
$ cat -n test0.h
1 struct foo
2 {
3 int m0;
4
5 foo()
6 : m0()
7 {}
8 };
9
10 foo*
11 first_func();
12
13 void
14 second_func(foo&);
15
16 void
17 third_func();
$
$ cat -n test-app.cc
1 // Compile with:
2 // g++ -g -Wall -o test-app -L. -ltest-0 test-app.cc
3
4 #include "test0.h"
5
6 int
7 main()
8 {
9 foo* f = first_func();
10 second_func(*f);
11 return 0;
12 }
$
$ cat -n test0.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-0.so test0.cc
3
4 #include "test0.h"
5
6 foo*
7 first_func()
8 {
9 foo* f = new foo();
10 return f;
11 }
12
13 void
14 second_func(foo&)
15 {
16 }
17
18 void
19 third_func()
20 {
21 }
$
$ cat -n test1.h
1 struct foo
2 {
3 int m0;
4 char m1; /* <-- a new member got added here! */
5
6 foo()
7 : m0(),
8 m1()
9 {}
10 };
11
12 foo*
13 first_func();
14
15 void
16 second_func(foo&);
17
18 void
19 third_func();
$
$ cat -n test1.cc
1 // Compile this with:
2 // g++ -g -Wall -shared -o libtest-1.so test1.cc
3
4 #include "test1.h"
5
6 foo*
7 first_func()
8 {
9 foo* f = new foo();
10 return f;
11 }
12
13 void
14 second_func(foo&)
15 {
16 }
17
18 /* Let's comment out the definition of third_func()
19 void
20 third_func()
21 {
22 }
23 */
$
· Compile the first and second versions of the libraries:
libtest-0.so and libtest-1.so:
$ g++ -g -Wall -shared -o libtest-0.so test0.cc
$ g++ -g -Wall -shared -o libtest-1.so test1.cc
· Compile the application and link it against the first version
of the library, creating the test-app binary:
$ g++ -g -Wall -o test-app -L. -ltest-0.so test-app.cc
· Now, use abicompat to see if libtest-1.so is ABI compatible
with app, with respect to the ABI of libtest-0.so:
$ abicompat test-app libtest-0.so libtest-1.so
ELF file 'test-app' might not be ABI compatible with 'libtest-1.so' due to differences with 'libtest-0.so' below:
Functions changes summary: 0 Removed, 2 Changed, 0 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
2 functions with some indirect sub-type change:
[C]'function foo* first_func()' has some indirect sub-type changes:
return type changed:
in pointed to type 'struct foo':
size changed from 32 to 64 bits
1 data member insertion:
'char foo::m1', at offset 32 (in bits)
[C]'function void second_func(foo&)' has some indirect sub-type changes:
parameter 0 of type 'foo&' has sub-type changes:
referenced type 'struct foo' changed, as reported earlier
$
· Now use the weak mode of abicompat, that is, providing just
the application and the new version of the library:
$ abicompat --weak-mode test-app libtest-1.so
functions defined in library
'libtest-1.so'
have sub-types that are different from what application
'test-app'
expects:
function foo* first_func():
return type changed:
in pointed to type 'struct foo':
size changed from 32 to 64 bits
1 data member insertion:
'char foo::m1', at offset 32 (in bits)
$
====== abidw ======
abidw reads a shared library in ELF format and emits an XML
representation of its ABI to standard output. The emitted
representation includes all the globally defined functions and
variables, along with a complete representation of their types. It
also includes a representation of the globally defined ELF symbols of
the file. The input shared library must contain associated debug
information in DWARF format.
When given the --linux-tree option, this program can also handle a
Linux kernel tree. That is, a directory tree that contains both the
vmlinux binary and Linux kernel modules. It analyses those Linux
kernel binaries and emits an XML representation of the interface
between the kernel and its module, to standard output. In this case,
we don't call it an ABI, but a KMI (Kernel Module Interface). The
emitted KMI includes all the globally defined functions and
variables, along with a complete representation of their types. The
input binaries must contain associated debug information in DWARF
format.
Invocation
abidw [options] [<path-to-elf-file>]
Options
· --help | -h
Display a short help about the command and exit.
· --version | -v
Display the version of the program and exit.
· --debug-info-dir | -d <dir-path>
In cases where the debug info for path-to-elf-file is in a
separate file that is located in a non-standard place, this
tells abidw where to look for that debug info file.
Note that dir-path must point to the root directory under which
the debug information is arranged in a tree-like manner. Under
Red Hat based systems, that directory is usually
<root>/usr/lib/debug.
Note that this option is not mandatory for split debug
information installed by your system's package manager because
then abidw knows where to find it.
· --out-file <file-path>
This option instructs abidw to emit the XML representation of
path-to-elf-file into the file file-path, rather than emitting
it to its standard output.
· --noout
This option instructs abidw to not emit the XML representation
of the ABI. So it only reads the ELF and debug information,
builds the internal representation of the ABI and exits. This
option is usually useful for debugging purposes.
· --no-corpus-path
Do not emit the path attribute for the ABI corpus.
· --suppressions | suppr <path-to-suppression-specifications-file>
Use a suppression specification file located at
path-to-suppression-specifications-file. Note that this option
can appear multiple times on the command line. In that case,
all of the provided suppression specification files are taken
into account. ABI artifacts matched by the suppression
specifications are suppressed from the output of this tool.
· --kmi-whitelist | -kaw <path-to-whitelist>
When analyzing a Linux kernel binary, this option points to the
white list of names of ELF symbols of functions and variables
which ABI must be written out. That white list is called a "
Kernel Module Interface white list". This is because for the
Kernel, we don't talk about the ABI; we rather talk about the
interface between the Kernel and its module. Hence the term KMI
rather than ABI
Any other function or variable which ELF symbol are not present
in that white list will not be considered by the KMI writing
process.
If this option is not provided -- thus if no white list is
provided -- then the entire KMI, that is, all publicly defined
and exported functions and global variables by the Linux Kernel
binaries is emitted.
· --linux-tree | --lt
Make abidw to consider the input path as a path to a directory
containing the vmlinux binary as several kernel modules
binaries. In that case, this program emits the representation
of the Kernel Module Interface (KMI) on the standard output.
Below is an example of usage of abidw on a Linux Kernel tree.
First, checkout a Linux kernel source tree and build it. Then
install the kernel modules in a directory somewhere. Copy the
vmlinux binary into that directory too. And then serialize the
KMI of that kernel to disk, using abidw:
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
$ cd linux && git checkout v4.5
$ make allyesconfig all
$ mkdir build-output
$ make INSTALL_MOD_PATH=./build-output modules_install
$ cp vmlinux build-output/modules/4.5.0
$ abidw --linux-tree build-output/modules/4.5.0 > build-output/linux-4.5.0.kmi
· --headers-dir | --hd <headers-directory-path-1>
Specifies where to find the public headers of the first shared
library that the tool has to consider. The tool will thus
filter out types that are not defined in public headers.
· --no-linux-kernel-mode
Without this option, if abipkgiff detects that the binaries it
is looking at are Linux Kernel binaries (either vmlinux or
modules) then it only considers functions and variables which
ELF symbols are listed in the __ksymtab and __ksymtab_gpl
sections.
With this option, abipkgdiff considers the binary as a
non-special ELF binary. It thus considers functions and
variables which are defined and exported in the ELF sense.
· --check-alternate-debug-info <elf-path>
If the debug info for the file elf-path contains a reference to
an alternate debug info file, abidw checks that it can find that
alternate debug info file. In that case, it emits a meaningful
success message mentioning the full path to the alternate debug
info file found. Otherwise, it emits an error code.
· --no-show-locs
Do not show information about where in the second shared
library the respective type was changed.
· --check-alternate-debug-info-base-name <elf-path>
Like --check-alternate-debug-info, but in the success message,
only mention the base name of the debug info file; not its full
path.
· --load-all-types
By default, libabigail (and thus abidw) only loads types that
are reachable from functions and variables declarations that are
publicly defined and exported by the binary. So only those
types are present in the output of abidw. This option however
makes abidw load all the types defined in the binaries, even
those that are not reachable from public declarations.
· --abidiff
Load the ABI of the ELF binary given in argument, save it in
libabigail's XML format in a temporary file; read the ABI from
the temporary XML file and compare the ABI that has been read
back against the ABI of the ELF binary given in argument. The
ABIs should compare equal. If they don't, the program emits a
diagnostic and exits with a non-zero code.
This is a debugging and sanity check option.
· --annotate
Annotate the ABIXML output with comments above most elements.
The comments are made of the pretty-printed form types,
declaration or even ELF symbols. The purpose is to make the
ABIXML output more human-readable for debugging or documenting
purposes.
· --stats
Emit statistics about various internal things.
· --verbose
Emit verbose logs about the progress of miscellaneous internal
things.
Notes
Alternate debug info files
As of the version 4 of the DWARF specification, Alternate debug
information is a GNU extension to the DWARF specification. It has
however been proposed for inclusion into the upcoming version 5 of
the DWARF standard. You can read more about the GNU extensions to
the DWARF standard here.
abilint
abilint parses the native XML representation of an ABI as emitted by
abidw. Once it has parsed the XML representation of the ABI, abilint
builds and in-memory model from it. It then tries to save it back to
an XML form, to standard output. If that read-write operation
succeeds chances are the input XML ABI representation is meaningful.
Note that the main intent of this tool to help debugging issues in
the underlying Libabigail library.
Note also that abilint can also read an ELF input file, build the
in-memory model for its ABI, and serialize that model back into XML
to standard output. In that case, the ELF input file must be
accompanied with its debug information in the DWARF format.
Invocation
abilint [options] [<abi-file1>]
Options
· --help
Display a short help message and exits.
· --version | -v
Display the version of the program and exit.
· --debug-info-dir <path>
When reading an ELF input file which debug information is split
out into a separate file, this options tells abilint where to
find that separate debug information file.
Note that path must point to the root directory under which the
debug information is arranged in a tree-like manner. Under Red
Hat based systems, that directory is usually
<root>/usr/lib/debug.
Note also that this option is not mandatory for split debug
information installed by your system's package manager because
then abidiff knows where to find it.
· --diff
For XML inputs, perform a text diff between the input and the
memory model saved back to disk. This can help to spot issues
in the handling of the XML format by the underlying Libabigail
library.
· --noout
Do not display anything on standard output. The return code of
the command is the only way to know if the command succeeded.
· --suppressions | suppr <path-to-suppression-specifications-file>
Use a suppression specification file located at
path-to-suppression-specifications-file. Note that this option
can appear multiple times on the command line. In that case,
all of the provided suppression specification files are taken
into account. ABI artifacts matched by the suppression
specifications are suppressed from the output of this tool.
· --headers-dir | --hd <headers-directory-path-1>
Specifies where to find the public headers of the first shared
library that the tool has to consider. The tool will thus
filter out types that are not defined in public headers.
· --stdin | --
Read the input content from standard input.
· --tu
Expect the input XML to represent a single translation unit.
fedabipkgdiff
fedabipkgdiff compares the ABI of shared libraries in Fedora
packages. It's a convenient way to do so without having to manually
download packages from the Fedora Build System.
fedabipkgdiff knows how to talk with the Fedora Build System to find
the right packages versions, their associated debug information and
development packages, download them, compare their ABI locally, and
report about the possible ABI changes.
Note that by default, this tool reports ABI changes about types that
are defined in public header files found in the development packages
associated with the packages being compared. It also reports ABI
changes about functions and global variables whose symbols are
defined and exported in the ELF binaries found in the packages being
compared.
Invocation
fedabipkgdiff [option] <NVR> ...
Environment
fedabipkgdiff loads two default suppression specifications files,
merges their content and use it to filter out ABI change reports that
might be considered as false positives to users.
· Default system-wide suppression specification file
It's located by the optional environment variable
LIBABIGAIL_DEFAULT_SYSTEM_SUPPRESSION_FILE. If that environment
variable is not set, then fedabipkgdiff tries to load the
suppression file $libdir/libabigail/libabigail-default.abignore.
If that file is not present, then no default system-wide
suppression specification file is loaded.
· Default user suppression specification file.
It's located by the optional environment
LIBABIGAIL_DEFAULT_USER_SUPPRESSION_FILE. If that environment
variable is not set, then fedabipkgdiff tries to load the
suppression file $HOME/.abignore. If that file is not present,
then no default user suppression specification is loaded.
Options
· --help | -h
Display a short help about the command and exit.
· --dry-run
Don't actually perform the ABI comparison. Details about what
is going to be done are emitted on standard output.
· --debug
Emit debugging messages about the execution of the program.
Details about each method invocation, including input parameters
and returned values, are emitted.
· --traceback
Show traceback when an exception raised. This is useful for
developers of the tool itself to know more exceptional errors.
· --server <URL>
Specifies the URL of the Koji XMLRPC service the tool talks to.
The default value of this option is
http://koji.fedoraproject.org/kojihub .
· --topurl <URL>
Specifies the URL of the package store the tool downloads RPMs
from. The default value of this option is
https://kojipkgs.fedoraproject.org .
· --from <distro>
Specifies the name of the baseline Fedora distribution in which
to find the first build that is used for comparison. The distro
value can be any valid value of the RPM macro %{?dist} for
Fedora, for example, fc4, fc23, fc25.
· --to <distro>
Specifies the name of the Fedora distribution in which to find
the build that is compared against the baseline specified by
option --from. The distro value could be any valid value of the
RPM macro %{?dist} for Fedora, for example, fc4, fc23.
· --all-subpackages
Instructs the tool to also compare the ABI of the binaries in
the sub-packages of the packages specified.
· --dso-only
Compares the ABI of shared libraries only. If this option is
not provided, the tool compares the ABI of all ELF binaries
found in the packages.
· --no-default-suppression
Do not load the default suppression specification files.
· --no-devel-pkg
Do not take associated development packages into account when
performing the ABI comparison. This makes the tool report ABI
changes about all types that are reachable from functions and
global variables which symbols are defined and publicly exported
in the binaries being compared, even if those types are not
defined in public header files available from the packages being
compared.
· --show-identical-binaries
Show the names of the all binaries compared, including the
binaries whose ABI compare equal. By default, when this
option is not provided, only binaries with ABI changes are
mentionned in the output.
· --abipkgdiff <path/to/abipkgdiff>
Specify an alternative abipkgdiff instead of the one installed
in system.
· --clean-cache-before
Clean cache before ABI comparison.
· --clean-cache-after
Clean cache after ABI comparison.
· --clean-cache
If you want to clean cache both before and after ABI comparison,
--clean-cache is the convenient way for you to save typing of
two options at same time.
Note that a build is a specific version and release of an RPM
package. It's specified by its the package name, version and
release. These are specified by the Fedora Naming Guidelines
Return value
The exit code of the abipkgdiff command is either 0 if the ABI of the
binaries compared are equivalent, or non-zero if they differ or if
the tool encountered an error.
In the later case, the value of the exit code is the same as for the
abidiff tool.
Use cases
Below are some usage examples currently supported by fedabipkgdiff.
1. Compare the ABI of binaries in a local package against the ABI
of the latest stable package in Fedora 23.
Suppose you have built just built the httpd package and you
want to compare the ABI of the binaries in this locally built
package against the ABI of the binaries in the latest http
build from Fedora 23. The command line invocation would be:
$ fedabipkgdiff --from fc23 ./httpd-2.4.18-2.fc24.x86_64.rpm
2. Compare the ABI of binaries in two local packages.
Suppose you have built two versions of package httpd, and you
want to see what ABI differences between these two versions of
RPM files. The command line invocation would be:
$ fedabipkgdiff path/to/httpd-2.4.23-3.fc23.x86_64.rpm another/path/to/httpd-2.4.23-4.fc24.x86_64.rpm
All what fedabipkgdiff does happens on local machine without
the need of querying or downloading RPMs from Koji.
3. Compare the ABI of binaries in the latest build of the httpd
package in Fedora 23 against the ABI of the binaries in the
latest build of the same package in 24.
In this case, note that neither of the two packages are
available locally. The tool is going to talk with the Fedora
Build System, determine what the versions and releases of the
latest packages are, download them and perform the comparison
locally. The command line invocation would be:
$ fedabipkgdiff --from fc23 --to fc24 httpd
4. Compare the ABI of binaries of two builds of the httpd package,
designated their versions and releases.
If we want to do perform the ABI comparison for all the
processor architectures supported by Fedora the command line
invocation would be:
$ fedabipkgdiff httpd-2.8.14.fc23 httpd-2.8.14.fc24
But if we want to perform the ABI comparison for a specific
architecture, say, x86_64, then the command line invocation
would be:
$ fedabipkgdiff httpd-2.8.14.fc23.x86_64 httpd-2.8.14.fc24.x86_64
5. If the use wants to also compare the sub-packages of a given
package, she can use the --all-subpackages option. The first
command of the previous example would thus look like:
$ fedabipkgdiff --all-subpackages httpd-2.8.14.fc23 httpd-2.8.14.fc24
ABI artifacts
An ABI artifact is a relevant part of the ABI of a shared library or
program. Examples of ABI artifacts are exported types, variables,
functions, or ELF symbols exported by a shared library.
The set of ABI artifact for a binary is called an ABI Corpus.
Harmful changes
A change in the diff report is considered harmful if it might cause
ABI compatibility issues. That is, it might prevent an application
dynamically linked against a given version of a library to keep
working with the changed subsequent versions of the same library.
Harmless changes
A change in the diff report is considered harmless if it will not
cause any ABI compatibility issue. That is, it will not prevent an
application dynamically linked against given version of a library to
keep working with the changed subsequent versions of the same
library.
By default, abidiff filters harmless changes from the diff report.
Suppression specifications
Definition
A suppression specification file is a way for a user to instruct
abidiff, abipkgdiff or any other relevant libabigail tool to avoid
emitting reports for changes involving certain ABI artifacts.
It contains directives (or specifications) that describe the set of
ABI artifacts to avoid emitting change reports about.
Introductory examples
Its syntax is based on a simplified and customized form of Ini File
Syntax. For instance, to specify that change reports on a type named
FooPrivateType should be suppressed, one could write this suppression
specification:
[suppress_type]
name = FooPrivateType
If we want to ensure that only change reports about structures named
FooPrivateType should be suppressed, we could write:
[suppress_type]
type_kind = struct
name = FooPrivateType
But we could also want to suppress change reports avoid typedefs
named FooPrivateType. In that case we would write:
[suppress_type]
type_kind = typedef
name = FooPrivateType
Or, we could want to suppress change reports about all struct which
names end with the string "PrivateType":
[suppress_type]
type_kind = struct
name_regexp = ^.*PrivateType
Let's now look at the generic syntax of suppression specification
files.
Syntax
Properties
More generally, the format of suppression lists is organized around
the concept of property. Every property has a name and a value,
delimited by the = sign. E.g:
name = value
Leading and trailing white spaces are ignored around property names
and values.
Regular expressions
The value of some properties might be a regular expression. In that
case, they must comply with the syntax of extended POSIX regular
expressions. Note that Libabigail uses the regular expression engine
of the GNU C Library.
Escaping a character in a regular expression
When trying to match a string that contains a * character, like in
the pointer type int*, one must be careful to notice that the
character * is a special character in the extended POSIX regular
expression syntax. And that character must be escaped for the
regular expression engine. Thus the regular expression that would
match the string int* in a suppression file should be
int\\*
Wait; but then why the two \ characters? Well, because the \
character is a special character in the Ini File Syntax used for
specifying suppressions. So it must be escaped as well, so that the
Ini File parser leaves a \ character intact in the data stream that
is handed to the regular expression engine. Hence the \\ targeted at
the Ini File parser.
So, in short, to escape a character in a regular expression, always
prefix the character with the \\ sequence.
Modus operandi
Suppression specifications can be applied at two different points of
the processing pipeline of libabigail.
In the default operating mode called "late suppression mode",
suppression specifications are applied to the result of comparing the
in-memory internal representations of two ABIs. In this mode, if an
ABI artifact matches a suppression specification, its changes are not
mentioned in the ABI change report. The internal representation of
the "suppressed" changed ABI artifact is still present in memory; it
is just not mentioned in the ABI change report. The change report
can still mention statistics about the number of changed ABI
artifacts that were suppressed.
There is another operating mode called the "early suppression mode"
where suppression specifications are applied during the construction
of the in-memory internal representation of a given ABI. In that
mode, if an ABI artifact matches a suppression specification, no
in-memory internal representation is built for it. As a result, no
change about the matched ABI artifact is going to be mentioned in the
ABI change report and no statistic about the number of suppressed ABI
changes is available. Also, please note that because suppressed ABI
artifacts are removed from the in-memory internal representation in
this mode, the amount memory used by the internal representation is
potentially smaller than the memory consumption in the late
suppression mode.
Sections
Properties are then grouped into arbitrarily named sections that
shall not be nested. The name of the section is on a line by itself
and is surrounded by square brackets, i.e:
[section_name]
property1_name = property1_value
property2_name = property2_value
A section might or might not have properties. Sections that expect
to have properties and which are found nonetheless empty are just
ignored. Properties that are not recognized by the reader are
ignored as well.
Section names
Each different section can be thought of as being a directive to
suppress ABI change reports for a particular kind of ABI artifact.
[suppress_file]
This directive prevents a given tool from loading a file (binary or
not) if its file name matches certain properties. Thus, if the tool
is meant to compare the ABIs of two files, and if the directive
prevents it from loading either one of the files, then no comparison
is performed.
Note that for the [suppress_file] directive to work, at least one of
the following properties must be provided:
file_name_regexp, file_name_not_regexp.
The potential properties of this sections are listed below:
· file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Prevents the system from loading the file which name matches the
regular expression specified as value of this property.
· file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Prevents the system from loading the file which name does not match
the regular expression specified as value of this property.
· label
Usage:
label = <some-value>
Define a label for the section. A label is just an informative
string that might be used by the tool to refer to a type
suppression in error messages.
[suppress_type]
This directive suppresses report messages about a type change.
Note that for the [suppress_type] directive to work, at least one of
the following properties must be provided:
file_name_regexp, file_name_not_regexp, soname_regexp,
soname_not_regexp, name, name_regexp, type_kind,
source_location_not_in, source_location_not_regexp.
If none of the following properties are provided, then the
[suppress_type] directive is simply ignored.
The potential properties of this sections are listed below:
· file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
binary file which name matches the regular expression specified as
value of this property.
· file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
binary file which name does not match the regular expression
specified as value of this property.
· soname_regexp
Usage:
soname_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
shared library which SONAME property matches the regular expression
specified as value of this property.
· soname_not_regexp
Usage:
soname_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
shared library which SONAME property does not match the regular
expression specified as value of this property.
· name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving types whose name matches the
regular expression specified as value of this property.
· name
Usage:
name = <a-value>
Suppresses change reports involving types whose name equals the
value of this property.
· type_kind
Usage:
type_kind = class | struct | union | enum |
array | typedef | builtin
Suppresses change reports involving a certain kind of type. The
kind of type to suppress change reports for is specified by the
possible values listed above:
·
class: suppress change reports for class types. Note that
even if class types don't exist for C, this value
still triggers the suppression of change reports for
struct types, in C. In C++ however, it should do
what it suggests.
·
struct: suppress change reports for struct types in C or
C++.
Note that the value class above is a super-set of
this one.
· union: suppress change reports for union types.
· enum: suppress change reports for enum types.
· array: suppress change reports for array types.
· typedef: suppress change reports for typedef types.
· builtin: suppress change reports for built-in (or native)
types. Example of built-in types are char, int, unsigned
int, etc.
· source_location_not_in
Usage:
source_location_not_in = <list-of-file-paths>
Suppresses change reports involving a type which is defined in a
file which path is NOT listed in the value list-of-file-paths.
Note that the value is a comma-separated list of file paths e.g,
this property
source_location_not_in = libabigail/abg-ir.h, libabigail/abg-dwarf-reader.h
suppresses change reports about all the types that are NOT defined
in header files whose path end up with the strings
libabigail/abg-ir.h or libabigail/abg-dwarf-reader.h.
· source_location_not_regexp
Usage:
source_location_not_regexp = <regular-expression>
Suppresses change reports involving a type which is defined in a
file which path does NOT match the regular expression provided as
value of the property. E.g, this property
source_location_not_regexp = libabigail/abg-.*\\.h
suppresses change reports involving all the types that are NOT
defined in header files whose path match the regular expression
provided a value of the property.
· has_data_member_inserted_at
Usage:
has_data_member_inserted_at = <offset-in-bit>
Suppresses change reports involving a type which has at least one
data member inserted at an offset specified by the property value
offset-in-bit. The value offset-in-bit is either:
· an integer value, expressed in bits, which denotes the
offset of the insertion point of the data member,
starting from the beginning of the relevant structure or
class.
· the keyword end which is a named constant which value
equals the offset of the end of the of the structure or
class.
· the function call expression offset_of(data-member-name)
where data-member-name is the name of a given data member
of the relevant structure or class. The value of this
function call expression is an integer that represents
the offset of the data member denoted by
data-member-name.
· the function call expression
offset_after(data-member-name) where data-member-name is
the name of a given data member of the relevant structure
or class. The value of this function call expression is
an integer that represents the offset of the point that
comes right after the region occupied by the data member
denoted by data-member-name.
· has_data_member_inserted_between
Usage:
has_data_member_inserted_between = {<range-begin>,
<range-end>}
Suppresses change reports involving a type which has at least one
data mber inserted at an offset that is comprised in the range
between range-begin`` and range-end. Please note that each of the
lues range-begin and range-end can be of the same form as the
has_data_member_inserted_at property above.
Usage examples of this properties are:
has_data_member_inserted_between = {8, 64}
or:
has_data_member_inserted_between = {16, end}
or:
has_data_member_inserted_between = {offset_after(member1), end}
· has_data_members_inserted_between
Usage:
has_data_members_inserted_between = {<sequence-of-ranges>}
Suppresses change reports involving a type which has multiple data
member inserted in various offset ranges. A usage example of this
property is, for instance:
has_data_members_inserted_between = {{8, 31}, {72, 95}}
This usage example suppresses change reports involving a type
which has data members inserted in bit offset ranges [8 31] and
[72 95]. The length of the sequence of ranges or this
has_data_members_inserted_between is not bounded; it can be as
long as the system can cope with. The values of the boundaries of
the ranges are of the same kind as for the
has_data_member_inserted_at property above.
Another usage example of this property is thus:
has_data_members_inserted_between =
{
{offset_after(member0), offset_of(member1)},
{72, end}
}
· accessed_through
Usage:
accessed_through = <some-predefined-values>
Suppress change reports involving a type which is referred to
either directly or through a pointer or a reference. The
potential values of this property are the predefined keywords
below:
· direct
So if the [suppress_type] contains the property description:
accessed_through = direct
then changes about a type that is referred-to directly (i.e,
not through a pointer or a reference) are going to be
suppressed.
· pointer
If the accessed_through property is set to the value pointer
then changes about a type that is referred-to through a
pointer are going to be suppressed.
· reference
If the accessed_through property is set to the value
reference then changes about a type that is referred-to
through a reference are going to be suppressed.
· reference-or-pointer
If the accessed_through property is set to the value
reference-or-pointer then changes about a type that is
referred-to through either a reference or a pointer are
going to be suppressed.
For an extensive example of how to use this property, please check
out the example below about suppressing change reports about types
accessed either directly or through pointers.
· drop
Usage:
drop = yes | no
If a type is matched by a suppression specification which contains
the "drop" property set to "yes" (or to "true") then the type is
not even going to be represented in the internal representation of
the ABI being analyzed. This property makes its enclosing
suppression specification to be applied in the early suppression
specification mode. The net effect is that it potentially reduces
the memory used to represent the ABI being analyzed.
Please note that for this property to be effective, the enclosing
suppression specification must have at least one of the following
properties specified: name_regexp, name, name_regexp,
source_location_not_in or source_location_not_regexp.
· label
Usage:
label = <some-value>
Define a label for the section. A label is just an informative
string that might be used by a tool to refer to a type suppression
in error messages.
[suppress_function]
This directive suppresses report messages about changes on a set of
functions.
Note that for the [suppress_function] directive to work, at least one
of the following properties must be provided:
label, file_name_regexp, file_name_not_regexp, soname_regexp,
soname_not_regexp, name, name_regexp, name_not_regexp, parameter,
return_type_name,
symbol_name, symbol_name_regexp, symbol_version,
symbol_version_regexp.
If none of the following properties are provided, then the
[suppress_function] directive is simply ignored.
The potential properties of this sections are:
· label
Usage:
label = <some-value>
This property is the same as the label property defined above.
· file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
binary file which name matches the regular expression specified as
value of this property.
· file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
binary file which name does not match the regular expression
specified as value of this property.
· soname_regexp
Usage:
soname_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
shared library which SONAME property matches the regular expression
specified as value of this property.
· soname_not_regexp
Usage:
soname_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
shared library which SONAME property does not match the regular
expression specified as value of this property.
· name
Usage:
name = <some-value>
Suppresses change reports involving functions whose name equals
the value of this property.
· name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving functions whose name matches
the regular expression specified as value of this property.
Let's consider the case of functions that have several symbol
names. This happens when the underlying symbol for the function
has aliases. Each symbol name is actually one alias name.
In this case, if the regular expression matches the name of at
least one of the aliases names, then it must match the names of
all of the aliases of the function for the directive to actually
suppress the diff reports for said function.
· name_not_regexp
Usage:
name_not_regexp = <regular-expression>
Suppresses change reports involving functions whose names don't
match the regular expression specified as value of this property.
The rules for functions that have several symbol names are the
same rules as for the name_regexp property above.
· change_kind
Usage:
change_kind = <predefined-possible-values>
Specifies the kind of changes this suppression specification
should apply to. The possible values of this property as well as
their meaning are listed below:
· function-subtype-change
This suppression specification applies to functions that
which have at least one sub-type that has changed.
· added-function
This suppression specification applies to functions that
have been added to the binary.
· deleted-function
This suppression specification applies to functions that
have been removed from the binary.
· all
This suppression specification applies to functions that
have all of the changes above. Note that not providing the
change_kind property at all is equivalent to setting it to
the value all.
· parameter
Usage:
parameter = <function-parameter-specification>
Suppresses change reports involving functions whose parameters
match the parameter specification indicated as value of this
property.
The format of the function parameter specification is:
' <parameter-index> <space> <type-name-or-regular-expression>
That is, an apostrophe followed by a number that is the index of
the parameter, followed by one of several spaces, followed by
either the name of the type of the parameter, or a regular
expression describing a family of parameter type names.
If the parameter type name is designated by a regular expression,
then said regular expression must be enclosed between two slashes;
like /some-regular-expression/.
The index of the first parameter of the function is zero. Note
that for member functions (methods of classes), the this is the
first parameter that comes after the implicit "this" pointer
parameter.
Examples of function parameter specifications are:
'0 int
Which means, the parameter at index 0, whose type name is int.
'4 unsigned char*
Which means, the parameter at index 4, whose type name is unsigned
char*.
'2 /^foo.*&/
Which means, the parameter at index 2, whose type name starts with
the string "foo" and ends with an '&'. In other words, this is
the third parameter and it's a reference on a type that starts
with the string "foo".
· return_type_name
Usage:
return_type_name = <some-value>
Suppresses change reports involving functions whose return type
name equals the value of this property.
· return_type_regexp
Usage:
return_type_regexp = <regular-expression>
Suppresses change reports involving functions whose return type
name matches the regular expression specified as value of this
property.
· symbol_name
Usage:
symbol_name = <some-value>
Suppresses change reports involving functions whose symbol name
equals the value of this property.
· symbol_name_regexp
Usage:
symbol_name_regexp = <regular-expression>
Suppresses change reports involving functions whose symbol name
matches the regular expression specified as value of this
property.
Let's consider the case of functions that have several symbol
names. This happens when the underlying symbol for the function
has aliases. Each symbol name is actually one alias name.
In this case, the regular expression must match the names of all
of the aliases of the function for the directive to actually
suppress the diff reports for said function.
· symbol_version
Usage:
symbol_version = <some-value>
Suppresses change reports involving functions whose symbol version
equals the value of this property.
· symbol_version_regexp
Usage:
symbol_version_regexp = <regular-expression>
Suppresses change reports involving functions whose symbol version
matches the regular expression specified as value of this
property.
· drop
Usage:
drop = yes | no
If a function is matched by a suppression specification which
contains the "drop" property set to "yes" (or to "true") then the
function is not even going to be represented in the internal
representation of the ABI being analyzed. This property makes its
enclosing suppression specification to be applied in the early
suppression specification mode. The net effect is that it
potentially reduces the memory used to represent the ABI being
analyzed.
Please note that for this property to be effective, the enclosing
suppression specification must have at least one of the following
properties specified: name_regexp, name, name_regexp,
source_location_not_in or source_location_not_regexp.
[suppress_variable]
This directive suppresses report messages about changes on a set of
variables.
Note that for the [suppress_variable] directive to work, at least one
of the following properties must be provided:
label, file_name_regexp, file_name_not_regexp, soname_regexp,
soname_not_regexp, name, name_regexp, symbol_name,
symbol_name_regexp, symbol_version, symbol_version_regexp.
If none of the following properties are provided, then the
[suppres_variable] directive is simply ignored.
The potential properties of this sections are:
· label
Usage:
label = <some-value>
This property is the same as the label property defined above.
· file_name_regexp
Usage:
file_name_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
binary file which name matches the regular expression specified as
value of this property.
· file_name_not_regexp
Usage:
file_name_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
binary file which name does not match the regular expression
specified as value of this property.
· soname_regexp
Usage:
soname_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
shared library which SONAME property matches the regular expression
specified as value of this property.
· soname_not_regexp
Usage:
soname_not_regexp = <regular-expression>
Suppresses change reports about ABI artifacts that are defined in a
shared library which SONAME property does not match the regular
expression specified as value of this property.
· name
Usage:
name = <some-value>
Suppresses change reports involving variables whose name equals
the value of this property.
· name_regexp
Usage:
name_regexp = <regular-expression>
Suppresses change reports involving variables whose name matches
the regular expression specified as value of this property.
· change_kind
Usage:
change_kind = <predefined-possible-values>
Specifies the kind of changes this suppression specification
should apply to. The possible values of this property as well as
their meaning are the same as when it's used in the
[suppress_function] section.
· symbol_name
Usage:
symbol_name = <some-value>
Suppresses change reports involving variables whose symbol name
equals the value of this property.
· symbol_name_regexp
Usage:
symbol_name_regexp = <regular-expression>
Suppresses change reports involving variables whose symbol name
matches the regular expression specified as value of this
property.
· symbol_version
Usage:
symbol_version = <some-value>
Suppresses change reports involving variables whose symbol version
equals the value of this property.
· symbol_version_regexp
Usage:
symbol_version_regexp = <regular-expression>
Suppresses change reports involving variables whose symbol version
matches the regular expression specified as value of this
property.
· type_name
Usage:
type_name = <some-value>
Suppresses change reports involving variables whose type name
equals the value of this property.
· type_name_regexp
Usage:
type_name_regexp = <regular-expression>
Suppresses change reports involving variables whose type name
matches the regular expression specified as value of this
property.
Comments
; or # ASCII character at the beginning of a line indicates a
comment. Comment lines are ignored.
Code examples
1. Suppressing change reports about types.
Suppose we have a library named libtest1-v0.so which contains this
very useful code:
$ cat -n test1-v0.cc
1 // A forward declaration for a type considered to be opaque to
2 // function foo() below.
3 struct opaque_type;
4
5 // This function cannot touch any member of opaque_type. Hence,
6 // changes to members of opaque_type should not impact foo, as far as
7 // ABI is concerned.
8 void
9 foo(opaque_type*)
10 {
11 }
12
13 struct opaque_type
14 {
15 int member0;
16 char member1;
17 };
$
Let's change the layout of struct opaque_type by inserting a data
member around line 15, leading to a new version of the library, that
we shall name libtest1-v1.so:
$ cat -n test1-v1.cc
1 // A forward declaration for a type considered to be opaque to
2 // function foo() below.
3 struct opaque_type;
4
5 // This function cannot touch any member of opaque_type; Hence,
6 // changes to members of opaque_type should not impact foo, as far as
7 // ABI is concerned.
8 void
9 foo(opaque_type*)
10 {
11 }
12
13 struct opaque_type
14 {
15 char added_member; // <-- a new member got added here now.
16 int member0;
17 char member1;
18 };
$
Let's compile both examples. We shall not forget to compile them
with debug information generation turned on:
$ g++ -shared -g -Wall -o libtest1-v0.so test1-v0.cc
$ g++ -shared -g -Wall -o libtest1-v1.so test1-v1.cc
Let's ask abidiff which ABI differences it sees between
libtest1-v0.so and libtest1-v1.so:
$ abidiff libtest1-v0.so libtest1-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void foo(opaque_type*)' has some indirect sub-type changes:
parameter 0 of type 'opaque_type*' has sub-type changes:
in pointed to type 'struct opaque_type':
size changed from 64 to 96 bits
1 data member insertion:
'char opaque_type::added_member', at offset 0 (in bits)
2 data member changes:
'int opaque_type::member0' offset changed from 0 to 32
'char opaque_type::member1' offset changed from 32 to 64
So abidiff reports that the opaque_type's layout has changed in a
significant way, as far as ABI implications are concerned, in theory.
After all, a sub-type (struct opaque_type) of an exported function
(foo()) has seen its layout change. This might have non negligible
ABI implications. But in practice here, the programmer of the
litest1-v1.so library knows that the "soft" contract between the
function foo() and the type struct opaque_type is to stay away from
the data members of the type. So layout changes of struct
opaque_type should not impact foo().
Now to teach abidiff about this soft contract and have it avoid
emitting what amounts to false positives in this case, we write the
suppression specification file below:
$ cat test1.suppr
[suppress_type]
type_kind = struct
name = opaque_type
Translated in plain English, this suppression specification would
read: "Do not emit change reports about a struct which name is
opaque_type".
Let's now invoke abidiff on the two versions of the library again,
but this time with the suppression specification:
$ abidiff --suppressions test1.suppr libtest1-v0.so libtest1-v1.so
Functions changes summary: 0 Removed, 0 Changed (1 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
As you can see, abidiff does not report the change anymore; it tells
us that it was filtered out instead.
Suppressing change reports about types with data member insertions
Suppose the first version of a library named libtest3-v0.so has this
source code:
/* Compile this with:
gcc -g -Wall -shared -o libtest3-v0.so test3-v0.c
*/
struct S
{
char member0;
int member1; /*
between member1 and member2, there is some padding,
at least on some popular platforms. On
these platforms, adding a small enough data
member into that padding shouldn't change
the offset of member1. Right?
*/
};
int
foo(struct S* s)
{
return s->member0 + s->member1;
}
Now, suppose the second version of the library named libtest3-v1.so
has this source code in which a data member has been added in the
padding space of struct S and another data member has been added at
its end:
/* Compile this with:
gcc -g -Wall -shared -o libtest3-v1.so test3-v1.c
*/
struct S
{
char member0;
char inserted1; /* <---- A data member has been added here... */
int member1;
char inserted2; /* <---- ... and another one has been added here. */
};
int
foo(struct S* s)
{
return s->member0 + s->member1;
}
In libtest3-v1.so, adding char data members S::inserted1 and
S::inserted2 can be considered harmless (from an ABI compatibility
perspective), at least on the x86 platform, because that doesn't
change the offsets of the data members S::member0 and S::member1.
But then running abidiff on these two versions of library yields:
$ abidiff libtest3-v0.so libtest3-v1.so
Functions changes summary: 0 Removed, 1 Changed, 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function int foo(S*)' has some indirect sub-type changes:
parameter 0 of type 'S*' has sub-type changes:
in pointed to type 'struct S':
type size changed from 64 to 96 bits
2 data member insertions:
'char S::inserted1', at offset 8 (in bits)
'char S::inserted2', at offset 64 (in bits)
$
That is, abidiff shows us the two changes, even though we (the
developers of that very involved library) know that these changes are
harmless in this particular context.
Luckily, we can devise a suppression specification that essentially
tells abidiff to filter out change reports about adding a data member
between S::member0 and S::member1, and adding a data member at the
end of struct S. We have written such a suppression specification in
a file called test3-1.suppr and it unsurprisingly looks like:
[suppress_type]
name = S
has_data_member_inserted_between = {offset_after(member0), offset_of(member1)}
has_data_member_inserted_at = end
Now running abidiff with this suppression specification yields:
$ ../build/tools/abidiff --suppressions test3-1.suppr libtest3-v0.so libtest3-v1.so
Functions changes summary: 0 Removed, 0 Changed (1 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
$
Hooora! \o/ (I guess)
Suppressing change reports about types accessed either directly or
through pointers
Suppose we have a first version of an object file which source code
is the file widget-v0.cc below:
// Compile with: g++ -g -c widget-v0.cc
struct widget
{
int x;
int y;
widget()
:x(), y()
{}
};
void
fun0(widget*)
{
// .. do stuff here.
}
void
fun1(widget&)
{
// .. do stuff here ..
}
void
fun2(widget w)
{
// ... do other stuff here ...
}
Now suppose in the second version of that file, named widget-v1.cc,
we have added some data members at the end of the type struct widget;
here is what the content of that file would look like:
// Compile with: g++ -g -c widget-v1.cc
struct widget
{
int x;
int y;
int w; // We have added these two new data members here ..
int h; // ... and here.
widget()
: x(), y(), w(), h()
{}
};
void
fun0(widget*)
{
// .. do stuff here.
}
void
fun1(widget&)
{
// .. do stuff here ..
}
void
fun2(widget w)
{
// ... do other stuff here ...
}
When we invoke abidiff on the object files resulting from the
compilation of the two file above, here is what we get:
$ abidiff widget-v0.o widget-v1.o
Functions changes summary: 0 Removed, 2 Changed (1 filtered out), 0 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
2 functions with some indirect sub-type change:
[C]'function void fun0(widget*)' has some indirect sub-type changes:
parameter 1 of type 'widget*' has sub-type changes:
in pointed to type 'struct widget':
type size changed from 64 to 128 bits
2 data member insertions:
'int widget::w', at offset 64 (in bits)
'int widget::h', at offset 96 (in bits)
[C]'function void fun2(widget)' has some indirect sub-type changes:
parameter 1 of type 'struct widget' has sub-type changes:
details were reported earlier
$
I guess a little bit of explaining is due here. abidiff detects that
two data member got added at the end of struct widget. it also tells
us that the type change impacts the exported function fun0() which
uses the type struct widget through a pointer, in its signature.
Careful readers will notice that the change to struct widget also
impacts the exported function fun1(), that uses type struct widget
through a reference. But then abidiff doesn't tell us about the
impact on that function fun1() because it has evaluated that change
as being redundant with the change it reported on fun0(). It has
thus filtered it out, to avoid cluttering the output with noise.
Redundancy detection and filtering is fine and helpful to avoid
burying the important information in a sea of noise. However, it
must be treated with care, by fear of mistakenly filtering out
relevant and important information.
That is why abidiff tells us about the impact that the change to
struct widget has on function fun2(). In this case, that function
uses the type struct widget directly (in its signature). It does not
use it via a pointer or a reference. In this case, the direct use of
this type causes fun2() to be exposed to a potentially harmful ABI
change. Hence, the report about fun2() is not filtered out, even
though it's about that same change on struct widget.
To go further in suppressing reports about changes that are harmless
and keeping only those that we know are harmful, we would like to go
tell abidiff to suppress reports about this particular struct widget
change when it impacts uses of struct widget through a pointer or
reference. In other words, suppress the change reports about fun0()
and fun1(). We would then write this suppression specification, in
file widget.suppr:
[suppress_type]
name = widget
type_kind = struct
has_data_member_inserted_at = end
accessed_through = reference-or-pointer
# So this suppression specification says to suppress reports about
# the type 'struct widget', if this type was added some data member
# at its end, and if the change impacts uses of the type through a
# reference or a pointer.
Invoking abidiff on widget-v0.o and widget-v1.o with this suppression
specification yields:
$ abidiff --suppressions widget.suppr widget-v0.o widget-v1.o
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function void fun2(widget)' has some indirect sub-type changes:
parameter 1 of type 'struct widget' has sub-type changes:
type size changed from 64 to 128 bits
2 data member insertions:
'int widget::w', at offset 64 (in bits)
'int widget::h', at offset 96 (in bits)
$
As expected, I guess.
Suppressing change reports about functions.
Suppose we have a first version a library named libtest2-v0.so whose
source code is:
$ cat -n test2-v0.cc
1 struct S1
2 {
3 int m0;
4
5 S1()
6 : m0()
7 {}
8 };
9
10 struct S2
11 {
12 int m0;
13
14 S2()
15 : m0()
16 {}
17 };
18
19 struct S3
20 {
21 int m0;
22
23 S3()
24 : m0()
25 {}
26 };
27
28 int
29 func(S1&)
30 {
31 // suppose the code does something with the argument.
32 return 0;
33
34 }
35
36 char
37 func(S2*)
38 {
39 // suppose the code does something with the argument.
40 return 0;
41 }
42
43 unsigned
44 func(S3)
45 {
46 // suppose the code does something with the argument.
47 return 0;
48 }
$
And then we come up with a second version libtest2-v1.so of that
library; the source code is modified by making the structures S1, S2,
S3 inherit another struct:
$ cat -n test2-v1.cc
1 struct base_type
2 {
3 int m_inserted;
4 };
5
6 struct S1 : public base_type // <--- S1 now has base_type as its base
7 // type.
8 {
9 int m0;
10
11 S1()
12 : m0()
13 {}
14 };
15
16 struct S2 : public base_type // <--- S2 now has base_type as its base
17 // type.
18 {
19 int m0;
20
21 S2()
22 : m0()
23 {}
24 };
25
26 struct S3 : public base_type // <--- S3 now has base_type as its base
27 // type.
28 {
29 int m0;
30
31 S3()
32 : m0()
33 {}
34 };
35
36 int
37 func(S1&)
38 {
39 // suppose the code does something with the argument.
40 return 0;
41
42 }
43
44 char
45 func(S2*)
46 {
47 // suppose the code does something with the argument.
48 return 0;
49 }
50
51 unsigned
52 func(S3)
53 {
54 // suppose the code does something with the argument.
55 return 0;
56 }
$
Now let's build the two libraries:
g++ -Wall -g -shared -o libtest2-v0.so test2-v0.cc
g++ -Wall -g -shared -o libtest2-v0.so test2-v0.cc
Let's look at the output of abidiff:
$ abidiff libtest2-v0.so libtest2-v1.so
Functions changes summary: 0 Removed, 3 Changed, 0 Added functions
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
3 functions with some indirect sub-type change:
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
parameter 0 of type 'struct S3' has sub-type changes:
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S3::m0' offset changed from 0 to 32
[C]'function char func(S2*)' has some indirect sub-type changes:
parameter 0 of type 'S2*' has sub-type changes:
in pointed to type 'struct S2':
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S2::m0' offset changed from 0 to 32
[C]'function int func(S1&)' has some indirect sub-type changes:
parameter 0 of type 'S1&' has sub-type changes:
in referenced type 'struct S1':
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S1::m0' offset changed from 0 to 32
$
Let's tell abidiff to avoid showing us the differences on the
overloads of func that takes either a pointer or a reference. For
that, we author this simple suppression specification:
$ cat -n libtest2.suppr
1 [suppress_function]
2 name = func
3 parameter = '0 S1&
4
5 [suppress_function]
6 name = func
7 parameter = '0 S2*
$
And then let's invoke abidiff with the suppression specification:
$ ../build/tools/abidiff --suppressions libtest2.suppr libtest2-v0.so libtest2-v1.so
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
parameter 0 of type 'struct S3' has sub-type changes:
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S3::m0' offset changed from 0 to 32
The suppression specification could be reduced using regular
expressions:
$ cat -n libtest2-1.suppr
1 [suppress_function]
2 name = func
3 parameter = '0 /^S.(&|\\*)/
$
$ ../build/tools/abidiff --suppressions libtest2-1.suppr libtest2-v0.so libtest2-v1.so
Functions changes summary: 0 Removed, 1 Changed (2 filtered out), 0 Added function
Variables changes summary: 0 Removed, 0 Changed, 0 Added variable
1 function with some indirect sub-type change:
[C]'function unsigned int func(S3)' has some indirect sub-type changes:
parameter 0 of type 'struct S3' has sub-type changes:
size changed from 32 to 64 bits
1 base class insertion:
struct base_type
1 data member change:
'int S3::m0' offset changed from 0 to 32
$
Dodji Seketeli
2014-2016, Red Hat, Inc.
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