Re: [PATCH] build: silence stupid gcc warning on STREQ_NULLABLE

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

 



On Mon, Aug 20, 2012 at 01:51:49PM -0600, Eric Blake wrote:
> Our existing STRNEQ_NULLABLE() triggered a warning in gcc 4.7 when
> used with a literal NULL argument:
> 
> qemumonitorjsontest.c: In function 'testQemuMonitorJSONGetMachines':
> qemumonitorjsontest.c:289:5: error: null argument where non-null required (argument 1) [-Werror=nonnull]
> 
> even though the strcmp is provably dead when a null argument is
> present.  Squelch the warning by refactoring things so that gcc
> never sees strcmp() called with NULL arguments (we still compare
> NULL as not equal to "", this rewrite merely aids gcc).
> 
> Next, gcc has a valid warning about a literal NULLSTR(NULL):
> 
> qemumonitorjsontest.c:289:5: error: invalid application of 'sizeof' to a void type [-Werror=pointer-arith]
> 
> Of course, you'd never write NULLSTR(NULL) directly, but it is
> handy to use through macros.  And since we only really need the
> code to be warning-free when developing with modern gcc, and
> merely compiled correctly elsewhere, we can rely on gcc extensions
> to avoid dereferencing NULL even inside a sizeof operation.
> 
> * src/internal.h (STREQ_NULLABLE, STRNEQ_NULLABLE): Avoid gcc 4.7
> stupidity.
> (NULLSTR): Allow passing compile-time constants via macros.
> ---
>  src/internal.h | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)

Not sure I entirely understand the GCC black magic, but if it works
for you I'll ACK

Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|

--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list


[Index of Archives]     [Virt Tools]     [Libvirt Users]     [Lib OS Info]     [Fedora Users]     [Fedora Desktop]     [Fedora SELinux]     [Big List of Linux Books]     [Yosemite News]     [KDE Users]     [Fedora Tools]