Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH V2 5/5] Tools: hv: kvp: Fix a warning of buffer overflow with gcc 8.0.1 | Date | Thu, 18 Oct 2018 15:08:34 +0000 |
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From: Dan Carpenter > Sent: 18 October 2018 07:33 > > On Thu, Oct 18, 2018 at 05:09:32AM +0000, kys@linuxonhyperv.com wrote: > > From: Dexuan Cui <decui@microsoft.com> > > > > The patch fixes: > > > > hv_kvp_daemon.c: In function 'kvp_set_ip_info': > > hv_kvp_daemon.c:1305:2: note: 'snprintf' output between 41 and 4136 bytes > > into a destination of size 4096 > > > > The "(unsigned int)str_len" is to avoid: > > > > hv_kvp_daemon.c:1309:30: warning: comparison of integer expressions of > > different signedness: 'int' and 'long unsigned int' [-Wsign-compare]
I usually use 'str_len + 0u' rather than a cast.
> Ugh... Any tool with the most basic flow analysis would realize this > was a false positive. We use at least three static analyzers which > catch signedness bugs. Can we turn off GCC's warning on this until they > improve it a bit?
Yes, would be nice if it attempted to follow the valid domain of variables.
I recently had to change: unsigned char a, b; unsigned int c; ... if (a + b < c) To stop a 'signedness' warning.
David
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