https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102316
Bug ID: 102316
Summary: Unexpected stringop-overflow Warnings on POWER CPU
Product: gcc
Version: 11.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: drc at linux dot vnet.ibm.com
Target Milestone: ---
Building DPDK with gcc (GCC) 11.1.1 20210531 (Red Hat 11.1.1-3) on a POWER9
host and powerpc64le-linux-gnu-gcc (GCC) 11.2.1 20210802 (Advance-Toolchain
15.0-0) [ebcfb7a665c2] on an x86_64 cross-compile host, generates the warning:
In function ‘i40e_flow_parse_fdir_pattern’,
inlined from ‘i40e_flow_parse_fdir_filter’ at
../drivers/net/i40e/i40e_flow.c:3274:8:
../drivers/net/i40e/i40e_flow.c:3052:69: warning: writing 1 byte into a region
of size 0 [-Wstringop-overflow=]
3052 | filter->input.flow_ext.flexbytes[j] =
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
3053 | raw_spec->pattern[i];
| ~~~~~~~~~~~~~~~~~~~~
In file included from ../drivers/net/i40e/i40e_flow.c:25:
../drivers/net/i40e/i40e_flow.c: In function ‘i40e_flow_parse_fdir_filter’:
../drivers/net/i40e/i40e_ethdev.h:630:17: note: at offset 16 into destination
object ‘flexbytes’ of size 16
630 | uint8_t flexbytes[RTE_ETH_FDIR_MAX_FLEXLEN];
| ^~~~~~~~~
See https://bugs.dpdk.org/show_bug.cgi?id=743 for additional details on DPDK
build failure.
Running cvise to reduce the failing code yields the following simplified test
failure:
#include <stdlib.h>
#define LEN 16
struct {
char c[LEN]
} d;
int a = LEN;
char* b;
int p() {
for (int i = 0; i < a; i++) {
d.c[i] = b[i];
}
return 0;
}
int main () {
int r = 0;
b = malloc(sizeof(char) * (LEN + 1));
r = p();
return r;
}
$ gcc -O3 test.c
test.c:6:1: warning: no semicolon at end of struct or union
6 | } d;
| ^
test.c: In function 'p':
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 16 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 17 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 18 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 19 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 20 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 21 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 22 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 23 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 24 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 25 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 26 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 27 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 28 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 29 into destination object 'c' of size 16
5 | char c[LEN]
| ^
test.c:13:12: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
13 | d.c[i] = b[i];
| ~~~~~~~^~~~~~
test.c:5:8: note: at offset 30 into destination object 'c' of size 16
5 | char c[LEN]
| ^
Compiling both the original DPDK and simplified code with -O3 for POWER systems
generates the given warnings, but compiling the code with -O2 for POWER systems
does not generate the warning.
Compiling the simplified code with either -O3 or -O2 for x86_64 systems does
not generate a warning.
