Re: [Qemu-devel] [PATCH] w32: Always use standard instead of native format strings

[Stefan Weil]

Am 24.09.2012 21:28, schrieb Eric Blake:
> On 08/22/2012 01:42 PM, Stefan Weil wrote:
> > GLib 2.0 include files use __printf__ for the format attribute
> > which resolves to native format strings on w32 hosts.
> >
> > QEMU wants standard format strings instead of native format
> > strings, so we simply change any declaration with __printf__
> > to use __gnu_printf__.
> >
> > This works because all basic printf functions support both
> > kinds of format strings.
> >
> > This fixes a compiler warning:
> >
> > qapi/string-output-visitor.c: In function ‘print_type_int’:
> > qapi/string-output-visitor.c:34:5: warning: unknown conversion type character 
> > ‘l’ in format [-Wformat]
> > qapi/string-output-visitor.c:34:5: warning: too many arguments for format 
> > [-Wformat-extra-args]
> >
> > Signed-off-by: Stefan Weil<address@hidden>
> > ---
> >   compiler.h |    5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/compiler.h b/compiler.h
> > index 07ba1f8..c734a71 100644
> > --- a/compiler.h
> > +++ b/compiler.h
> > @@ -44,6 +44,11 @@
> >      /* Use gnu_printf when supported (qemu uses standard format strings). */
> >   #  define GCC_ATTR __attribute__((__unused__, format(gnu_printf, 1, 2)))
> >   #  define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
> > +#  if defined(_WIN32)
> > +    /* Map __printf__ to __gnu_printf__ because we want standard format strings
> > +     * even when MinGW or GLib include files use __printf__. */
> > +#   define __printf__ __gnu_printf__
> > +#  endif
>
> Don't you need to make this conditional on the gcc version?  That is,
> gcc 4.4 added __gnu_printf__, but gcc 4.3 understands only __printf__
> and attempts to pass __gnu_printf__ will cause compilation failure.

It is conditional. The complete code is here:

# if !QEMU_GNUC_PREREQ(4, 4)
   /* gcc versions before 4.4.x don't support gnu_printf, so use printf. */
#  define GCC_ATTR __attribute__((__unused__, format(printf, 1, 2)))
#  define GCC_FMT_ATTR(n, m) __attribute__((format(printf, n, m)))
# else
   /* Use gnu_printf when supported (qemu uses standard format strings). */
#  define GCC_ATTR __attribute__((__unused__, format(gnu_printf, 1, 2)))
#  define GCC_FMT_ATTR(n, m) __attribute__((format(gnu_printf, n, m)))
#  if defined(_WIN32)
    /* Map __printf__ to __gnu_printf__ because we want standard format 
strings
     * even when MinGW or GLib include files use __printf__. */
#   define __printf__ __gnu_printf__
#  endif
# endif

gcc 4.3 and older will still produce compiler warnings.