https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109298
Bug ID: 109298
Summary: warning: array subscript ‘...’ is partly outside array
bounds of ‘...’
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: ubizjak at gmail dot com
Target Milestone: ---
This warning/error is actually emitted when compiling
drivers/infiniband/core/user_mad.c linux source file.
The testcase:
--cut here--
enum {
IB_MGMT_RMPP_HDR = 36,
IB_MGMT_RMPP_DATA = 220,
};
struct ib_umad_packet {
int hdr;
unsigned char data[];
};
struct ib_rmpp_mad {
int class;
unsigned char data[IB_MGMT_RMPP_DATA];
};
int foo (const unsigned char *buf)
{
struct ib_umad_packet *packet;
struct ib_rmpp_mad *rmpp_mad;
packet = __builtin_malloc (sizeof *packet + IB_MGMT_RMPP_HDR);
__builtin_memcpy (&packet->data, buf, IB_MGMT_RMPP_HDR);
rmpp_mad = (struct ib_rmpp_mad *) packet->data;
return rmpp_mad->class;
}
--cut here--
-O2 -Wall
test.c: In function ‘foo’:
test.c:27:18: warning: array subscript ‘struct ib_rmpp_mad[0]’ is partly
outside array bounds of ‘unsigned char[40]’ [-Warray-bounds=]
27 | return rmpp_mad->class;
| ^~
test.c:21:12: note: at offset 4 into object of size 40 allocated by
‘__builtin_malloc’
21 | packet = __builtin_malloc (sizeof *packet + IB_MGMT_RMPP_HDR);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Adding -fno-strict-aliasing to compile flags does not help.
