[Bug c/59749] New: unused warning not emited for unused static struct unles -save-temps is used

["martin at netbsd dot org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59749

            Bug ID: 59749
           Summary: unused warning not emited for unused static struct
                    unles -save-temps is used
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: martin at netbsd dot org

Created attachment 31793
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31793&action=edit
original source file exhibiting the problem

I have a program (for the atf testing framework) that is supposed to warn about
an unused variable and (due to -Werror) fail compilation. This works fine with
gcc 4.5.4.

But with 4.8.2 I get:

$ /usr/pkg/gcc48/bin/cc -O2 -c -Wall -Werror /usr/tests/atf/atf-c/unused_test.c
$

The code (after macro expansion) declares a struct and initialize it:

static atfu_this_is_unused_tc_pack = { .m_ident = .... };

and there is no reference to this struct anywhere in the file.

Interestingly when preparing for this ticket I did:

$ /usr/pkg/gcc48/bin/cc -O2 -save-temps -c -Wall -Werror
/usr/tests/atf/atf-c/unused_test.c
/usr/tests/atf/atf-c/unused_test.c:41:123: error: 'atfu_this_is_unused_tc'
defined but not used [-Werror=unused-variable]
 ATF_TC(this_is_unused);
                                                                               
                                           ^
cc1: all warnings being treated as errors
$   /usr/pkg/gcc48/bin/cc -v                             Using built-in specs.
COLLECT_GCC=/usr/pkg/gcc48/bin/cc
COLLECT_LTO_WRAPPER=/usr/pkg/gcc48/libexec/gcc/sparc64--netbsd/4.8.2/lto-wrapper
Target: sparc64--netbsd
Configured with: ../gcc-4.8.2/configure --enable-languages='c c++'
--enable-shared --enable-long-long --with-local-prefix=/usr/pkg/gcc48
--enable-libssp --enable-threads=posix --with-boot-ldflags='-static-libstdc++
-static-libgcc -Wl,-R/usr/pkg/lib ' --with-gnu-ld --with-ld=/usr/bin/ld
--with-gnu-as --with-as=/usr/bin/as --disable-nls --with-gmp=/usr/pkg
--with-mpc=/usr/pkg --with-mpfr=/usr/pkg --enable-__cxa_atexit
--with-gxx-include-dir=/usr/pkg/gcc48/include/c++/ --prefix=/usr/pkg/gcc48
--build=sparc64--netbsd --host=sparc64--netbsd --infodir=/usr/pkg/gcc48/info
--mandir=/usr/pkg/gcc48/man
Thread model: posix
gcc version 4.8.2 (GCC)