[Bug tree-optimization/82042] New: signed integer overflow in ao_ref_init_from_ptr_and_size

["msebor at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82042

            Bug ID: 82042
           Summary: signed integer overflow in
                    ao_ref_init_from_ptr_and_size
           Product: gcc
           Version: 8.0
            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: ---

When compiled with today's top of trunk (GCC 8.0) configured for x86_64-linux
--with-build-config=bootstrap-ubsan the following test case triggers a runtime
error in the ao_ref_init_from_ptr_and_size() function in tree-ssa-alias.c
(besides a number of others).

$ cat t.c && gcc -O2 -S -Wall -ftracer t.c

char *p;

extern char a[];

void f (int i)
{
  __SIZE_TYPE__ idx = __SIZE_MAX__ / 2 - 1;
  p = __builtin_stpcpy (&a[idx], i ? "123" : "12345");
}

/src/gcc/git/gcc/tree-ssa-alias.c:704:30: runtime error: signed integer
overflow: 9223372036854775806 * 8 cannot be represented in type 'long int'
/src/gcc/git/gcc/alias.c:2583:21: runtime error: signed integer overflow:
-9223372036854775806 - 9223372036854775806 cannot be represented in type 'long
int'
/src/gcc/git/gcc/cse.c:2195:10: runtime error: signed integer overflow:
-9223372036854775805 - 9223372036854775806 cannot be represented in type 'long
int'
/src/gcc/git/gcc/dse.c:932:38: runtime error: signed integer overflow:
9223372036854775806 + 4 cannot be represented in type 'long int'
/src/gcc/git/gcc/dse.c:1539:28: runtime error: signed integer overflow: 4 +
9223372036854775806 cannot be represented in type 'long int'