[Bug c++/57241] New: GCC still issues -Wmultichar warnings despite a #pragma diagnostic ignored -Wmultichar directive

[scottbaldwin at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57241

            Bug ID: 57241
           Summary: GCC still issues -Wmultichar warnings despite a
                    #pragma diagnostic ignored -Wmultichar directive
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: scottbaldwin at gmail dot com

In GCC 4.7.2 and 4.8.x, the #pragma ignore directive for -Wmultichar has no
effect. The code below demonstrates a -Wmultichar which is still emitted as a
warning despite the #pragma directive to ignore it. Specifying -Wno-multichar
on the command line works fine, so this is just an issue with trying to
suppress it with a #pragma directive (which I need for finer-grained control).

Note: I didn't test the other diagnostic options to see if there are others
besides -Wmultichar that have the same issue, so you might want to do a full
check on all diagnostic options.

Here's the demo code and unsuppressed compiler warnings:

int main() {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmultichar"
    typedef boost::mpl::string<'0123', '4567', '89ab', 'cdef'> hex_chars; //
-Wmultichar (gcc still issues warnings, despite #pragma ignore directive)
#pragma GCC diagnostic pop
    return 0;
}

warnings in gcc 4.7.2:
    sandbox_cpp11.cpp:148:29: warning: multi-character character constant
[-Wmultichar]
    sandbox_cpp11.cpp:148:37: warning: multi-character character constant
[-Wmultichar]
    sandbox_cpp11.cpp:148:45: warning: multi-character character constant
[-Wmultichar]
    sandbox_cpp11.cpp:148:53: warning: multi-character character constant
[-Wmultichar]

warnings in gcc 4.8.x:
    sandbox_cpp11.cpp:148:29: warning: multi-character character constant
[-Wmultichar]
      typedef boost::mpl::string<'0123', '4567', '89ab', 'cdef'> hex_chars;
                                 ^
    sandbox_cpp11.cpp:148:37: warning: multi-character character constant
[-Wmultichar]
      typedef boost::mpl::string<'0123', '4567', '89ab', 'cdef'> hex_chars;
                                         ^
    sandbox_cpp11.cpp:148:45: warning: multi-character character constant
[-Wmultichar]
      typedef boost::mpl::string<'0123', '4567', '89ab', 'cdef'> hex_chars;
                                                 ^
    sandbox_cpp11.cpp:148:53: warning: multi-character character constant
[-Wmultichar]
      typedef boost::mpl::string<'0123', '4567', '89ab', 'cdef'> hex_chars;