[Bug c/60784] New: Spurious -Wmissing-field-initializers warning for anonymous structure

[peter at lekensteyn dot nl]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60784

            Bug ID: 60784
           Summary: Spurious -Wmissing-field-initializers warning for
                    anonymous structure
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: peter at lekensteyn dot nl

When an anonymous structure gets initialized, gcc always starts complaining
about the last field:
//////////////////////////////////////////
gcc -Wextra warn.c -o /dev/null
//////////////////////////////////////////
struct foo {
    struct {
        char a;
        char b;
    };
};

int main(void) {
    struct foo test = {
        .a = 1,
        .b = 2,
    };

    return test.a == 1;
}
///////////////////////////////////////////

Output:
warn.c: In function ‘main’:
warn.c:12:9: warning: missing initializer for field ‘b’ of ‘struct <anonymous>’
[-Wmissing-field-initializers]
         .b = 2,
         ^
warn.c:5:14: note: ‘b’ declared here
         char b;
              ^

It gets even worse when adding more fields. For fun, add "char c;" between
"char a;" and "char b;". The first warning mentions "c", but the line
thereafter points to "b":
warn.c: In function ‘main’:
warn.c:13:9: warning: missing initializer for field ‘c’ of ‘struct <anonymous>’
[-Wmissing-field-initializers]
         .b = 2,
         ^
warn.c:5:14: note: ‘c’ declared here
         char c;
              ^

Expected result: no warnings for the first case.

This is gcc-multilib 4.8.2-8 on Arch Linux x86_64.

COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-unknown-linux-gnu/4.8.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: /build/gcc-multilib/src/gcc-4.8-20140206/configure
--prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man
--infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++ --enable-shared
--enable-threads=posix --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-clocale=gnu --disable-libstdcxx-pch
--disable-libssp --enable-gnu-unique-object --enable-linker-build-id
--enable-cloog-backend=isl --disable-cloog-version-check --enable-lto
--enable-plugin --enable-install-libiberty --with-linker-hash-style=gnu
--enable-multilib --disable-werror --enable-checking=release
Thread model: posix
gcc version 4.8.2 20140206 (prerelease) (GCC)