f78 Getting the Return or Frame Address of a Function Contents|Index|Previous|Next

Getting the return or frame address of a function

The following calls may be used to get information about the callers of a function.

__builtin_return_address (level)

This function returns the return address of the current function, or of one of its callers. The

level

argument is number of frames to scan up the call stack. A value of

yields the return address of the current function, a value of

yields the return address of the caller of the current function, and so forth.

The level argument must be a constant integer. On some machines it may be impossible to determine the return address of any function other than the current one; in such cases, or when the top of the stack has been reached, this function will return 0.

This function should only be used with a non-zero argument for debugging purposes.

__builtin_frame_address ( level)

This function is similar to

__builtin_return_address

, but it returns the address of the function frame rather than the return address of the function. Calling

__builtin_frame_ address

with a value of

yields the frame address of the current function, a value of

yields the frame address of the caller of the current function, and so forth. The frame is the area on the stack which holds local variables and saved registers. The frame address is normally the ad-dress of the first word pushed on to the stack by the function. However, the exact definition depends upon the processor and the calling convention. If the processor has a dedicated frame pointer register, and the function has a frame, then

__builtin_frame_address

will ret 165 urn the value of the frame pointer register.

The caveats that apply to __builtin_return_address apply to this function as well.