[Bug c++/55881] New: #pragma GCC diagnostic ignored ignored when inlining

["greened at obbligato dot org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55881

             Bug #: 55881
           Summary: #pragma GCC diagnostic ignored ignored when inlining
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: greened@obbligato.org


The following testcase causes g++ 4.7.1 to emit a warning even though it
contains a pragma to ignore uninitialized variables.

struct I {
  int i;
  int foo(struct I *n) {
    // Warning points here.
    return n->i + 10;
  }

  I(void) : i(5) {}
};

int main(int argc, char **)
{
  struct I i, *n;

  if (argc > 10) {
    n = new I;
    // Fine.
    i.i = i.foo(n);
  }

  if (argc > 2) {
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
    // Still get a warning.
    return i.foo(n);
#pragma GCC diagnostic pop
  }

  return 0;
}

This is the shortest testcase I could produce to demonstrate the problem.  I
have seen this kind of problem when passing what gcc things are possibly
uninitialized variables as arguments to functions which are inlined.

Adding a pragma inside the inlined function suppresses the warning but that's a
much bigger hammer than placing the pragma around the call site.  I do not want
to miss possible errors in other contexts where the function is called.