Introduction
Dehydra represents C++ types and variables as JavaScript objects. The objects are designed to distill that type system to the minimum such that it can be easy to match on.
Often, the best way to become familiar with the Dehydra objects is to print out the objects:
- Dehydra example code
- an online tool for pretty-printing dehydra data
Understanding Properties
Dehydra only sets properties that are applicable. For example, class types and typedefs are declared and will have a .loc property. Intrinsic types such as "int" are not declared and will not have a .loc.
Dehydra only sets boolean flags when they are true. For example, a pointer type will have .isPointer == true, but a class type will not have an .isPointer property.
Common Properties
| Property | Type | Description |
.loc | location object | Source location of a type or declaration. |
.attributes | array of objects | Attributes of the type or declaration. Each member of the array has the following properties:
{
name: string,
value: string or number, if applicable
}
See an example on enforcing final classes. Code can be annotated with arbitrary user attributes: __attribute__((user("customstring"))). |
Variable Objects
Dehydra presents AST nodes as variables. These types are used to represent variables, functions, assignments, etc. The following properties are usually available:
| Property | Type | Description |
.name | string | The function or variable name. |
.type | type object | The type of this function or variable. |
.isStatic | boolean flag | |
.isReturn | boolean flag | The variable is being returned. |
.isDecl | boolean flag | The variable is being declared (local variables only). |
.assign | array of variable objects | This variable is the LHS of an assignment. The value is an array of values that were assigned. |
.isFcall | boolean flag | The variable is being used as a function call. |
.arguments | array of variable objects | Arguments used to make a function call. |
.parameters | array of variable objects | A function definition's parameter names and types |
.memberOf | aggregate type object | Indicates the aggregate type(class/struct) in the type system that this variable is a member of. |
.fieldOf | variable object | Provides the object being dereferenced, in the AST system. Applicable when accessing member variables or nonstatic member functions of aggregate types, e.g. the "foo" variable would be a .fieldOf memberVar/Fn in foo->memberVar or foo->memberFn(). Note that when constructing the return value of a function (e.g. return T();), no container variable is available; in this case, .isReturn will be true (see Function Variable). |
Variables can identified by their DehydraDecl() prototype.
Function Variable
Function objects are an extension of Variable Objects. The following additional properties are available on functions:
| Property | Type | Description |
.isVirtual | true or "pure" | true for virtual methods, or "pure" for pure virtuals (e.g. virtual void foo() = 0;). |
.isConstructor | boolean flag | Constructors generally have a .fieldOf attribute (see Variable Objects). |
.isFunction | boolean flag | true for function variables. |
Type Objects
Dehydra provides detailed type objects. Dehydra Type objects use the DehydraType() prototype.
Common Type Properties
| Property | Type | Description |
.name | string | If applicable, the name of of the type. For typedefs and classes, this is the declared name. For built-in types this is the standard name such as "int". Some types such as bitfields may not have names. |
.typedef | type object | If this is a typedef, the original type. |
.isConst | boolean flag | |
.isVolatile | boolean flag | |
.variantOf | type object | "const int" and "int" are separate types in GCC; the const version is considered a variant of the normal version. The variantOf property allows access to the original type object. |
.hasDefault | boolean flag | Applicable to function parameters only. Indicates whether the parameter has a default value, e.g. void foo(int i = 42). |
Aggregate Types (class/struct/union/enum)
This type object represents aggregate types in GCC.
| Property | Type | Description |
.kind | string | One of "class", "struct", "union", or "enum". |
.isIncomplete | boolean flag | the type was forward-declared and the full declaration has not been processed. |
.bases | array of objects | Inheritance information about the class. Each member of the array has the following properties:
{
access: 'public' | 'protected' | 'private',
type: type object representing the base class
}
|
.members | array of variable objects | An array containing all the member variables and methods. Note: the .members will not include static member functions. |
.template | template object | The template from which this class was instantiated, if applicable. |
Pointer and Reference Types
| Property | Type | Description |
.isPointer | boolean flag | |
.isReference | boolean flag | |
.type | type object | The type this points to or references |
Array Type
| Property | Type | Description |
.isArray | boolean flag | |
.max | integer | or normal fixed-size arrays, the index of the largest element of the array. For example, an int[10] would have .max = 9 |
.variableLength | boolean flag | true if the type represents a C99 variable-length array type |
Number Type
| Property | Type | Description |
.precision | integer | for floating-point types, the precision of the type |
.min | integer | for integer types, the minimum value capable of being stored |
.max | integer | for integer types, the maximum value capable of being stored |
.isSigned | boolean flag | for integer types, true if the type stores signed values |
.isUnsigned | boolean flag | for integer types, true if the type stores unsigned values |
.bitfieldBits | integer | if the type represents a bitfield, the number of bits used by the bitfield |
.bitfieldOf | number type object | if the type represents a bitfield, the base type of the bitfield. |
Function Type
These represent the types functions and methods in the type system:
| Property | Type | Description |
.type | type object | the function return type. |
.parameters | array of type objects | the parameter types for the function. |
.isExplicit | boolean flag | true for constructors declared using the C++ explicit keyword |
Template Objects
| Property | Type | Description |
.name | string | the name of the template, for example "nsCOMPtr". |
.arguments | array | an array where arguments are either strings representing C++ constants or type objects. |
Location Objects
Location objects are passed to builtin functions such as warning() and error() to specify the location of the message. They convert to a string of the form "file:line:column". They have the following properties:
| Property | Type |
.file | string |
.line | integer |
.column | integer (optional) |