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

[Martin Kletzander]

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 at 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
>--
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