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__BUILTIN_RETURN_ADDRESS(3)                           Library Functions Manual

NAME
     __builtin_return_address -- the return address of a function

SYNOPSIS
     void *
     __builtin_return_address(unsigned int level);

     void *
     __builtin_frame_address(unsigned int level);

DESCRIPTION
     The __builtin_return_address() is a GNU extension for obtaining the
     return address of the current function or one of the callers of the
     current function.

     The parameter level specifies the number of frames that should be scanned
     up in the call stack.  A value 0 returns the address of the current
     function, a value 1 requests the address of the caller of the current
     function, a value 2 asks for the address of the caller's caller, and so
     forth.  If the top of the call stack has been reached, the function will
     return 0.  Note also that on some architectures it is only possible to
     determine the address of the current function.  In such cases a value 0
     is returned.  Thus, it is usually safe to only use the value 0 for level.

     The __builtin_frame_address() behaves similarly, but returns the address
     of the function frame rather than the return address of the function.

SEE ALSO
     gcc(1), __builtin_object_size(3)

CAVEATS
     These are non-standard, compiler-specific extensions.

NetBSD 6.1.5                   December 19, 2010                  NetBSD 6.1.5