On Wed, Apr 05, 2017 at 12:38:23PM +0200, Martin Kletzander wrote:
On Wed, Apr 05, 2017 at 10:06:22AM +0100, Daniel P. Berrange wrote:
On Tue, Apr 04, 2017 at 09:51:47PM +0200, Martin Kletzander wrote:
On Tue, Apr 04, 2017 at 04:10:59PM +0100, Daniel P. Berrange wrote:
On Tue, Mar 28, 2017 at 01:46:31PM +0200, Martin Kletzander wrote:
The attribute (defined as ATTRIBUTE_NONNULL) was added long time ago (2009), but in 2012 (commit eefb881d4683) it was disabled for normal build, making it used only when coverity was building libvirt or on special request. It was disabled because it was being misused and misunderstood -- the attribute is there as an optimization hint for the compiler, not to enhance static analysis.
Actually the attribute does both and the primary intention of the attribute *is* build time warnings and/or static analysis warnings:
[quote] 'nonnull (ARG-INDEX, ...)' The 'nonnull' attribute specifies that some function parameters should be non-null pointers. For instance, the declaration:
extern void * my_memcpy (void *dest, const void *src, size_t len) __attribute__((nonnull (1, 2)));
causes the compiler to check that, in calls to 'my_memcpy', arguments DEST and SRC are non-null. If the compiler determines
This, however, happens only if we pass NULL directly. There's not much of a deeper analysis involved IIRC.
Yep, coverity is needed to do most deeper analysis of NULL handling
The use of nonnull attribute would help the compiler report mistakes, but the compiler only catches some easy cases at build time.
It would. But for now it is only enabled if STATIC_ANALYSIS=1 and that is only set if you are running in coverity (or explicitly specify that during configure, which almost nobody does).
Easily solvable by enabling it in CI.
How about we enable it by default for build with new enough GCC (so that it reports these errors without silently dropping the non-NULL checks)?
Yes, it seems that we can use -fno-delete-null-pointer-checks to prevent GCC from optimizing away the NULL pointer checks, while having nonnull attributes enabled all the time. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|