https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122764
Bug ID: 122764
Summary: -Warray-bounds false negative
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: [email protected]
Target Milestone: ---
alx@devuan:~/tmp$ cat bo.c
void f(int n, int a[n])
{
a[n + 100] = 42;
}
void g(int n, int (*a)[n])
{
(*a)[n + 100] = 42;
}
void h(int a[10])
{
a[10 + 100] = 42;
}
void i(int (*a)[10])
{
(*a)[10 + 100] = 42;
}
alx@devuan:~/tmp$ gcc -Wall -Wextra -O3 -fanalyzer -S bo.c
bo.c: In function ‘h’:
bo.c:11:10: warning: array subscript 110 is outside array bounds of ‘int[10]’
[-Warray-bounds=]
11 | a[10 + 100] = 42;
| ~^~~~~~~~~~
bo.c:9:12: note: at offset 440 into object ‘a’ of size [0, 40]
9 | void h(int a[10])
| ~~~~^~~~~
bo.c: In function ‘i’:
bo.c:15:13: warning: array subscript 110 is above array bounds of ‘int[10]’
[-Warray-bounds=]
15 | (*a)[10 + 100] = 42;
| ~~~~^~~~~~~~~~
bo.c:13:14: note: while referencing ‘a’
13 | void i(int (*a)[10])
| ~~~~~~^~~~~~
Would it be possible to diagnose this? The compiler doesn't know the value of
n, but it should know that n+100 is not within the bounds of the array.
