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Re: [libvirt] [PATCH] maint: update to latest gnulib



On Wed, Jun 14, 2017 at 04:30:49PM +0200, Martin Kletzander wrote:
> On Wed, Jun 14, 2017 at 02:32:41PM +0100, Daniel P. Berrange wrote:
> > On Wed, Jun 14, 2017 at 03:27:25PM +0200, Martin Kletzander wrote:
> > > On Wed, Jun 14, 2017 at 11:20:44AM +0100, Daniel P. Berrange wrote:
> > > > This fixes an incompatibility with glibc 2.25.90
> > > >
> > > > Signed-off-by: Daniel P. Berrange <berrange redhat com>
> > > > ---
> > > >
> > > > Pushed as a broken build fix to get CI back online
> > > >
> > > 
> > > After this update the build fails for me with gcc-7.1.0 with the
> > > following error:
> > > 
> > > In file included from util/virobject.c:28:0:
> > > util/virobject.c: In function 'virClassNew':
> > > util/viratomic.h:176:46: error: this condition has identical branches [-Werror=duplicated-branches]
> > >             (void)(0 ? *(atomic) ^ *(atomic) : 0);                      \
> > >                                              ^
> > > util/virobject.c:144:20: note: in expansion of macro 'virAtomicIntInc'
> > >     klass->magic = virAtomicIntInc(&magicCounter);
> > >                    ^~~~~~~~~~~~~~~
> > > 
> > > Does that mean that gcc does optimize our prefetch trick away
> > > (considering I understood what that line is trying to do)?  Or should we
> > > just turn the warning off for that header file?
> > 
> > Yep, "-Wduplicated-branches" appears to be a new warning flag in gcc 7.1
> > which gnulib turns on. There's a similar hit with mingw
> > 
> > ../../src/util/vircommand.c: In function 'virCommandWait':
> > ../../src/util/vircommand.c:2562:51: error: this condition has identical branches [-Werror=duplicated-branches]
> >             *exitstatus = cmd->rawStatus ? status : WEXITSTATUS(status);
> >                                                   ^
> > cc1: all warnings being treated as errors
> > 
> > 
> > because WEXITSTATUS(x) expands to 'x' on Win32.
> > 
> > We could use a pragma to turn off selectively, but I'm more
> > inclined to just disable this new warning flag.
> > 
> 
> Well, I'm not sure how that affects the line where we actually use it
> (with the atomic variables) or whether that line is not needed anymore
> (if that was a fix for older compilers or something similar).  But I
> can send a patch for removing that warning.  How about the other
> warning we get when we turn off the first one?  I just found out.  I
> think that could be turned off as well, either for some particular
> places or for the whole build:
> 
> util/virtime.c: In function 'virTimeStringThenRaw':
> util/virtime.c:215:9: error: '%02d' directive output may be truncated writing between 2 and 11 bytes into a region of size between 5 and 21 [-Werror=format-truncation=]
>     if (snprintf(buf, VIR_TIME_STRING_BUFLEN,
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>                  "%4d-%02d-%02d %02d:%02d:%02d.%03d+0000",
>                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>                  fields.tm_year, fields.tm_mon, fields.tm_mday,
>                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>                  fields.tm_hour, fields.tm_min, fields.tm_sec,
>                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>                  (int) (when % 1000)) >= VIR_TIME_STRING_BUFLEN) {
>                  ~~~~~~~~~~~~~~~~~~~~
> util/virtime.c:215:9: note: using the range [-2147483648, 2147483647] for directive argument
> In file included from /usr/include/stdio.h:936:0,
>                 from ../gnulib/lib/stdio.h:43,
>                 from util/virtime.c:36:
> /usr/include/bits/stdio2.h:64:10: note: '__builtin___snprintf_chk' output between 29 and 89 bytes into a destination of size 29
>   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>        __bos (__s), __fmt, __va_arg_pack ());
>        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I think we might just want to switch to asprintf here instead of trying to
optimize into a fixed stack allocated buffer.


Regards,
Daniel
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