https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86622
Bug ID: 86622
Summary: incorrect strlen of array of array plus variable
offset
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
As discussed in https://gcc.gnu.org/ml/gcc-patches/2018-07/msg01215.html, GCC
emits incorrect code for the following test case:
$ cat c.c && gcc c.c && ./a.out
static const char a[3][8] = { "1234", "12345", "123456" };
int main ()
{
volatile int i = 1;
int n = __builtin_strlen (*(&a[1] + i));
if (n != 6)
__builtin_abort ();
}
Aborted (core dumped)
The root cause is the handling of POINTER_PLUS expressions in
string_constant(). The original code (before the handling of aggregates was
added in r262522) just dealt with string constants. The new code does much
more but doesn't get this case right in these cases.
