[Bug libstdc++/58710] New: HAVE_GETIPINFO is incorrectly set on Mac OS X 10.4

["misty at brew dot sh" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58710

            Bug ID: 58710
           Summary: HAVE_GETIPINFO is incorrectly set on Mac OS X 10.4
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: misty at brew dot sh

_Unwind_GetIPInfo isn't available on Mac OS X 10.4 and older. GCC checks for
this specific case in several places to ensure it isn't used inappropriately,
but there seem to be a few issues that cause it to be used anyway. See #56811
for an example of this.

When checking for whether to use the system unwind, configure scripts
specifically check for Darwin 8 and older (see, for example, libbacktrace's
configure at L11629-11648); when Darwin 8 is encountered it explicitly sets
have_unwind_getipinfo to 0 to ensure it won't be used. However, the same
configure script also later does an independent check to see if
_Unwind_GetIPInfo is available, and this is erroneously reporting that it's
available. As a result several libraries, like libbacktrace, try to use
_UnwindGetIPInfo and the build fails at the link stage.

When I took a look at the config.log, it seems it's compiling using `-c`, so
the linker is inhibited:

configure:11652: checking for _Unwind_GetIPInfo
configure:11667: /usr/local/bin/gcc-4.4 -c -g
-Werror-implicit-function-declaration  conftest.c >&5
configure:11667: $? = 0
configure:11674: result: yes

However, the specific problem on OS X 10.4 is that _Unwind_GetIPInfo isn't
exported - and so the test would only fail if the linker was invoked.

I've noticed that a few sections of GCC, such as raise-gcc.c, appear to expect
that they'll get an incorrect configure value and redefine it themselves:

#ifdef __APPLE__
/* On MacOS X, versions older than 10.5 don't export _Unwind_GetIPInfo.  */
#undef HAVE_GETIPINFO
#if __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 1050
#define HAVE_GETIPINFO 1
#endif
#endif

However, this isn't done consistently, which is why other places (like
_Unwind_GetIPInfo) still try to use it.