[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

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



On Wed, Jun 14, 2017 at 03:35:39PM +0100, Daniel P. Berrange wrote:
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.


I wanted to do that and started rewriting it, but I found out we use
static buffers in lot of places and lot of them then use snprintf or
similar.  In some cases it doesn't even make much of a sense, e.g.:

 snprintf(buf, 3, "%d", var)

even this can fail.  I get the reason for the warning, but I don't
really agree that it's something that is necessary to avoid, so I'm
inclining to ignoring that warning as well.


Regards,
Daniel
--
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|

Attachment: signature.asc
Description: Digital signature


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]