Hi,
starting with gcc 4.3 G_STMT_START and G_STMT_END produce a "ambiguous 'else'" compiler warning in some cases but only when compiling in C++ mode (i.e. using g++ instead of gcc for example). One small example code is at the bottom.

The warning is caused by the following expansion:

if (123)
  if (1) {
    printf ("123");
  } else
    (void) 0;

and of course the warning is correct there. Forcing it to use the __extension__ variant of G_STMT_START/STOP in gmacros.h removes this warning, defining HAVE_DOWHILE_MACROS has the same effect. Is it a bug in my code that HAVE_DOWHILE_MACROS is not defined normally? Shouldn't this be documented somewhere that this is necessary for those macros then?


#include <stdio.h>
#include <glib.h>

#define foo(x) \
  G_STMT_START { \
    printf (x); \
  } G_STMT_END

int main()
{
  if (123)
    foo ("123");
  return 0;
}