[Bug tree-optimization/63989] New: tree-ssa-strlen.c doesn't handle constant pointer plus and array refs if constant offset is smaller than known constant string length

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63989

            Bug ID: 63989
           Summary: tree-ssa-strlen.c doesn't handle constant pointer plus
                    and array refs if constant offset is smaller than
                    known constant string length
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
                CC: dimhen at gmail dot com, jakub at gcc dot gnu.org,
                    nheghathivhistha at gmail dot com, rguenth at gcc dot 
gnu.org,
                    trippels at gcc dot gnu.org
        Depends on: 61773
            Blocks: 63787

+++ This bug was initially created as a clone of Bug #61773 +++

char *foo (void)
{
  char *p = __builtin_malloc (64);
  char *q = __builtin_malloc (64);
  __builtin_strcat (q, "abcde");
  __builtin_strcat (p, "ab");
  p[1] = q[3];
  __builtin_strcat (p, q);
  return q;
}

gives

> ../../obj2/gcc/cc1 -quiet -O2 t.c
t.c: In function ‘foo’:
t.c:1:7: internal compiler error: in get_string_length, at
tree-ssa-strlen.c:417
 char *foo (void)
       ^
0x876c3d2 get_string_length
        /space/rguenther/tramp3d/trunk/gcc/tree-ssa-strlen.c:417
0x8772b02 get_string_length
        /space/rguenther/tramp3d/trunk/gcc/tree.h:2731
0x8772b02 handle_builtin_strlen
        /space/rguenther/tramp3d/trunk/gcc/tree-ssa-strlen.c:899

(gdb) up
#1  0x0876c3d3 in get_string_length (si=0x3c)
    at /space/rguenther/tramp3d/trunk/gcc/tree-ssa-strlen.c:417
417           gcc_assert (builtin_decl_implicit_p (BUILT_IN_STPCPY));


while trying to write a testcase that shows that handle_char_store should
handle a character copy from a known non-zero value.  Well, while really
trying to incrementally teach handle_char_store to handle arbitrary
stores.