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 :|