https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92630
Bug ID: 92630
Summary: missing -Wrestrict with attribute access and restrict
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
Besides out-of-bounds reads and writes, the new attribute access also makes it
possible to detect overlapping copies. Calls in all four functions below
should be diagnosed as suggested in the comments.
$ cat t.c && gcc -O2 -S -Wall -Wextra t.c
typedef __SIZE_TYPE__ size_t;
void* memcpy (void* restrict, const void* restrict, size_t);
__attribute__ ((access (write_only, 1, 3), access (read_only, 2, 3))) void
f0 (void* restrict, const void *restrict, unsigned);
char a[8];
void f1 (void)
{
memcpy (a, a + 2, 8); // -Wstringop-overflow (good)
}
void f2 (void)
{
memcpy (a, a + 2, 4); // -Wsrestrict (good)
}
__attribute__ ((access (write_only, 1, 3), access (read_only, 2, 3))) void
mycpy (void* restrict, const void *restrict, unsigned);
void g1 (void)
{
mycpy (a, a + 2, 8); // warning (good)
}
void g2 (void)
{
mycpy (a, a + 2, 4); // missing -Wsrestrict
}
t.c: In function ‘f2’:
t.c:17:3: warning: ‘memcpy’ accessing 4 bytes at offsets 0 and 2 overlaps 2
bytes at offset 2 [-Wrestrict]
17 | memcpy (a, a + 2, 4); // -Wsrestrict (good)
| ^~~~~~~~~~~~~~~~~~~~
t.c: In function ‘f1’:
t.c:12:3: warning: ‘memcpy’ forming offset [8, 9] is out of the bounds [0, 8]
of object ‘a’ with type ‘char[8]’ [-Warray-bounds]
12 | memcpy (a, a + 2, 8); // warning (good)
| ^~~~~~~~~~~~~~~~~~~~
t.c:8:6: note: ‘a’ declared here
8 | char a[8];
| ^
t.c: In function ‘g1’:
t.c:25:3: warning: ‘mycpy’ reading 8 bytes from a region of size 6
[-Wstringop-overflow=]
25 | mycpy (a, a + 2, 8); // -Wstringop-overflow (good)
| ^~~~~~~~~~~~~~~~~~~
t.c:21:1: note: in a call to function ‘mycpy’ declared with attribute
‘read_only (2, 3)’
21 | mycpy (void* restrict, const void *restrict, unsigned);
| ^~~~~
