[C++ PATCH] Fix option handling when -std=gnu++14 is not used (PR 69865)

[Bernd Edlinger]

On 19.02.2016 12:31, Jakub Jelinek wrote:
> On Fri, Feb 19, 2016 at 11:08:48AM +0000, Bernd Edlinger wrote:
> > On 19.02.2016 11:56, Jakub Jelinek wrote:
> > >
> > > On Fri, Feb 19, 2016 at 10:50:34AM +0000, Bernd Edlinger wrote:
> > > > While I think that we should probably not define __GNUC_GNU_INLINE__ at all for C++,
> > > > because it is meaningless, I am warned that this could break (already broken) header files.
> > >
> > > It is not meaningless.  The various headers need to know if it is safe to
> > > use the gnu_inline attribute in C++.
> > >
> > > In any case, the desirable state is that e.g. the -E -dD output should be
> > > identical if you explicitly request the default -std= version vs. if it is
> > > set implicitly.  We should verify it is the case even for C.
> > >
> > >         Jakub
> >
> > I absolutely agree with you.
> > The correct solution is probably doing this:
> >
> > --- gcc/cp/cfns.h.jj  2016-01-04 15:30:50.000000000 +0100
> > +++ gcc/cp/cfns.h     2016-02-19 12:00:15.730375049 +0100
> > @@ -124,9 +124,6 @@
> >
> >  #ifdef __GNUC__
> >  __inline
> > -#ifdef __GNUC_STDC_INLINE__
> > -__attribute__ ((__gnu_inline__))
> > -#endif
> >  #endif
> >  const char *
> >  libc_name_p (register const char *str, register unsigned int len)
> 
> This is of course wrong.  cfns.h is a generated header, so you shouldn't
> patch it.
> If it is regenerated with a newer gperf (I have 3.0.4 installed), you get there:
> @@ -124,7 +124,7 @@ hash (register const char *str, register
> 
>  #ifdef __GNUC__
>  __inline
> -#ifdef __GNUC_STDC_INLINE__
> +#if defined __GNUC_STDC_INLINE__ || defined __GNUC_GNU_INLINE__
>  __attribute__ ((__gnu_inline__))
>  #endif
>  #endif
> 
>         Jakub

Damnit!!

I dont know how this file is ever supposed to compile on a C99 compiler.
but with this change it does not even compile with -std=c90 any more:

cat test.c
#include "cfns.h"

gcc -std=c90 test.c
In file included from test.c:1:0:
cfns.gperf:101:1: error: 'gnu_inline' attribute present on 'libc_name_p'
cfns.gperf:26:14: error: but not here

gcc -std=c99 test.c
In file included from test.c:1:0:
cfns.gperf:101:1: error: 'gnu_inline' attribute present on 'libc_name_p'
cfns.gperf:26:14: error: but not here
cfns.gperf: In function 'libc_name_p':
cfns.gperf:328:34: warning: implicit declaration of function 'strcmp' [-Wimplicit-function-declaration]


So this leaves only one solution, to define neither __GNUC_STDC_INLINE__
nor __GNUC_GNU_INLINE__ for C++, at least the inline and gnu_inline
is completely different on C and C++. But I am anxious this will break more
things than gperf, and I would like to fix this in a safe way.


Bernd.