Hi,
On s390-32|64 i get the following build warning
"sysdeps/s390/s390-64/backtrace.c:133:24: warning: the comparison will
always evaluate as âfalseâ for the address of â_Unwind_Backtraceâ will
never be NULL [-Waddress]" for the non SHARED case.
In SHARED case, the _Unwind_Backtrace function is loaded via dlsym() and
thus needs to be NULL-checked (if (unwind_backtrace == NULL)) in order
to fallback to __backchain_backtrace() function.
In non SHARED case, the #define unwind_backtrace _Unwind_Backtrace was
introduced with "* sysdeps/s390/s390-32/backtrace.c (init): Guard with
#ifdef SHARED." (Roland McGrath <roland@gnu.org> 2004-06-11 22:12:55)
and the NULL-check will never be false for _Unwind_Backtrace() function.
Thus this NULL-check is now only evaluated in SHARED-case.
The __backchain_backtrace function is only used in the SHARED-case,
if the unwind-function is not found. Thus it is now only compiled in the
SHARED-case, to avoid the warning: warning: â__backchain_backtraceâ
defined but not used [-Wunused-function].
On s390-32, this function is declared as static, but not on s390-64.
These functions were introduced in the same patch
"Update." (Ulrich Drepper <drepper@redhat.com> 2003-12-06 01:20:16)
and the Changelog from Martin Schwidefsky says:
* sysdeps/s390/s390-32/backtrace.c (trace_arg): New structure.
(unwind_backtrace, unwind_getip): New variables.
(init, __backchain_backtrace, backtrace_helper): New functions.
(__backtrace): Use unwind info for backtrace instead of backchain
walking if the unwind functions can be found.
* sysdeps/s390/s390-64/backtrace.c: Likewise.
On s390-64 it isnÂt exported in the shared library, thus on s390-64 it
is now declared as static too!
Bye Stefan
---
2014-10-07 Stefan Liebler <stli@linux.vnet.ibm.com>
* sysdeps/s390/s390-32/backtrace.c (__backtrace):
Check for unwind_backtrace == NULL only in SHARED case.
(__backchain_backtrace): Compile only in SHARED case.
* sysdeps/s390/s390-64/backtrace.c (__backtrace):
Likewise.
(__backchain_backtrace): Declare as static.