11.10.4 Functions for C++ ¶

A function is represented by a FUNCTION_DECL node. A set of overloaded functions is sometimes represented by an OVERLOAD node.

An OVERLOAD node is not a declaration, so none of the ‘DECL_’ macros should be used on an OVERLOAD. An OVERLOAD node is similar to a TREE_LIST. Use OVL_CURRENT to get the function associated with an OVERLOAD node; use OVL_NEXT to get the next OVERLOAD node in the list of overloaded functions. The macros OVL_CURRENT and OVL_NEXT are actually polymorphic; you can use them to work with FUNCTION_DECL nodes as well as with overloads. In the case of a FUNCTION_DECL, OVL_CURRENT will always return the function itself, and OVL_NEXT will always be NULL_TREE.

To determine the scope of a function, you can use the DECL_CONTEXT macro. This macro will return the class (either a RECORD_TYPE or a UNION_TYPE) or namespace (a NAMESPACE_DECL) of which the function is a member. For a virtual function, this macro returns the class in which the function was actually defined, not the base class in which the virtual declaration occurred.

If a friend function is defined in a class scope, the DECL_FRIEND_CONTEXT macro can be used to determine the class in which it was defined. For example, in

class C { friend void f() {} };

the DECL_CONTEXT for f will be the global_namespace, but the DECL_FRIEND_CONTEXT will be the RECORD_TYPE for C.

The following macros and functions can be used on a FUNCTION_DECL:

DECL_MAIN_P ¶

This predicate holds for a function that is the program entry point ::code.

DECL_LOCAL_FUNCTION_P ¶

This predicate holds if the function was declared at block scope, even though it has a global scope.

DECL_ANTICIPATED ¶

This predicate holds if the function is a built-in function but its prototype is not yet explicitly declared.

DECL_EXTERN_C_FUNCTION_P ¶

This predicate holds if the function is declared as an ‘extern "C"’ function.

DECL_LINKONCE_P ¶

This macro holds if multiple copies of this function may be emitted in various translation units. It is the responsibility of the linker to merge the various copies. Template instantiations are the most common example of functions for which DECL_LINKONCE_P holds; G++ instantiates needed templates in all translation units which require them, and then relies on the linker to remove duplicate instantiations.

FIXME: This macro is not yet implemented.

DECL_FUNCTION_MEMBER_P ¶

This macro holds if the function is a member of a class, rather than a member of a namespace.

DECL_STATIC_FUNCTION_P ¶

This predicate holds if the function a static member function.

DECL_NONSTATIC_MEMBER_FUNCTION_P ¶

This macro holds for a non-static member function.

DECL_CONST_MEMFUNC_P ¶

This predicate holds for a const-member function.

DECL_VOLATILE_MEMFUNC_P ¶

This predicate holds for a volatile-member function.

DECL_CONSTRUCTOR_P ¶

This macro holds if the function is a constructor.

DECL_NONCONVERTING_P ¶

This predicate holds if the constructor is a non-converting constructor.

DECL_COMPLETE_CONSTRUCTOR_P ¶

This predicate holds for a function which is a constructor for an object of a complete type.

DECL_BASE_CONSTRUCTOR_P ¶

This predicate holds for a function which is a constructor for a base class sub-object.

DECL_COPY_CONSTRUCTOR_P ¶

This predicate holds for a function which is a copy-constructor.

DECL_DESTRUCTOR_P ¶

This macro holds if the function is a destructor.

DECL_COMPLETE_DESTRUCTOR_P ¶

This predicate holds if the function is the destructor for an object a complete type.

DECL_OVERLOADED_OPERATOR_P ¶

This macro holds if the function is an overloaded operator.

DECL_CONV_FN_P ¶

This macro holds if the function is a type-conversion operator.

DECL_GLOBAL_CTOR_P ¶

This predicate holds if the function is a file-scope initialization function.

DECL_GLOBAL_DTOR_P ¶

This predicate holds if the function is a file-scope finalization function.

DECL_THUNK_P ¶

This predicate holds if the function is a thunk.

These functions represent stub code that adjusts the this pointer and then jumps to another function. When the jumped-to function returns, control is transferred directly to the caller, without returning to the thunk. The first parameter to the thunk is always the this pointer; the thunk should add THUNK_DELTA to this value. (The THUNK_DELTA is an int, not an INTEGER_CST.)

Then, if THUNK_VCALL_OFFSET (an INTEGER_CST) is nonzero the adjusted this pointer must be adjusted again. The complete calculation is given by the following pseudo-code:

this += THUNK_DELTA
if (THUNK_VCALL_OFFSET)
  this += (*((ptrdiff_t **) this))[THUNK_VCALL_OFFSET]

Finally, the thunk should jump to the location given by DECL_INITIAL; this will always be an expression for the address of a function.

DECL_NON_THUNK_FUNCTION_P ¶

This predicate holds if the function is not a thunk function.

GLOBAL_INIT_PRIORITY ¶

If either DECL_GLOBAL_CTOR_P or DECL_GLOBAL_DTOR_P holds, then this gives the initialization priority for the function. The linker will arrange that all functions for which DECL_GLOBAL_CTOR_P holds are run in increasing order of priority before main is called. When the program exits, all functions for which DECL_GLOBAL_DTOR_P holds are run in the reverse order.

TYPE_RAISES_EXCEPTIONS ¶

This macro returns the list of exceptions that a (member-)function can raise. The returned list, if non NULL, is comprised of nodes whose TREE_VALUE represents a type.

TYPE_NOTHROW_P ¶

This predicate holds when the exception-specification of its arguments is of the form ‘()’.

DECL_ARRAY_DELETE_OPERATOR_P ¶

This predicate holds if the function an overloaded operator delete[].