https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84732
Bug ID: 84732
Summary: false-positive -Wstringop-truncation warning with
-fsanitize-coverage=trace-pc
Product: gcc
Version: 8.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: arnd at linaro dot org
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
Created attachment 43576
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43576&action=edit
linux/drivers/staging/lustre/lnet/lnet/lib-socket.c, preprocessed, not reduced
I ran into this warning for what looks like correct code in the linux kernel
that we should not warn about:
$ aarch64-linux-gcc-8.0.1 -fno-strict-aliasing -Wno-pointer-sign
-fsanitize-coverage=trace-pc -Wall -O2 -c lib-socket.i
In file included from /git/arm-soc/arch/arm64/include/asm/processor.h:37,
from /git/arm-soc/arch/arm64/include/asm/spinlock.h:21,
from /git/arm-soc/include/linux/spinlock.h:88,
from /git/arm-soc/include/linux/wait.h:9,
from /git/arm-soc/include/linux/net.h:23,
from
/git/arm-soc/drivers/staging/lustre/lnet/lnet/lib-socket.c:37:
/git/arm-soc/drivers/staging/lustre/lnet/lnet/lib-socket.c: In function
'lnet_ipif_query':
/git/arm-soc/include/linux/string.h:254:9: warning: '__builtin_strncpy'
specified bound 16 equals destination size [-Wstringop-truncation]
return __builtin_strncpy(p, q, size);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/git/arm-soc/include/linux/string.h:254:9: warning: '__builtin_strncpy'
specified bound 16 equals destination size [-Wstringop-truncation]
return __builtin_strncpy(p, q, size);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/git/arm-soc/include/linux/string.h:254:9: warning: '__builtin_strncpy'
specified bound 16 equals destination size [-Wstringop-truncation]
return __builtin_strncpy(p, q, size);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
See
https://elixir.bootlin.com/linux/v4.15/source/drivers/staging/lustre/lnet/lnet/lib-socket.c#L99
for the original source code. Without -fsanitize-coverage=trace-pc, the
strlen() comparison is sufficient to avoid that warning, with
fsanitize=coverage=trace-pc, that logic fails:
if (strlen(name) > sizeof(ifr.ifr_name) - 1)
return -E2BIG;
strncpy(ifr.ifr_name, name, sizeof(ifr.ifr_name));
I can probably create a reduced test case if that helps.
