https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88992
Bug ID: 88992
Summary: missing -Warray-bounds indexing into a zero-length
array
Product: gcc
Version: 9.0
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: ---
Also while adding a test for the fix for bug 88956 I noticed that GCC doesn't
diagnose indexing into zero-length arrays. The out-of-bounds accesses to the
global zero-length arrays are folded to zero while those to the local ones are
emitted.
$ gcc -O2 -S -Wall t.c
const char s1[1] = { };
int f1 (void)
{
return s1[3]; // -Warray-bounds (good)
}
const char s0[0] = { };
int f0 (void)
{
return s0[3]; // missing warning
}
int g1 (void)
{
const char s1[1] = { };
return s1[3]; // -Warray-bounds (good)
}
int g0 (void)
{
const char s0[0] = { };
return s0[3]; // missing warning
}
t.c: In function ‘f1’:
t.c:4:12: warning: array subscript 3 is above array bounds of ‘const char[1]’
[-Warray-bounds]
4 | return s1[3]; // -Warray-bounds (good)
| ~~^~~
t.c:1:12: note: while referencing ‘s1’
1 | const char s1[1] = { };
| ^~
t.c: In function ‘g1’:
t.c:17:12: warning: array subscript 3 is above array bounds of ‘const char[1]’
[-Warray-bounds]
17 | return s1[3]; // -Warray-bounds (good)
| ~~^~~
t.c:16:14: note: while referencing ‘s1’
16 | const char s1[1] = { };
| ^~
