Hi,
As mentioned in PR, the issue is that cddce1 marks the call to
__builtin_strdup as necessary:
marking necessary through .MEM_6 stmt p_7 = __builtin_strdup (&d);

and since p_7 doesn't get added to worklist in propagate_necessity()
because it's used only within free(), it's treated as "dead"
and wrongly gets released.
The patch fixes that by adding strdup/strndup in corresponding condition
in eliminate_unnecessary_stmts().

Another issue, was that my previous patch failed to remove multiple
calls to strdup:
char *f(char **tt)
{
  char *t = *tt;
  char *p;

  p = __builtin_strdup (t);
  p = __builtin_strdup (t);
  return p;
}

That's fixed in patch by adding strdup/strndup to another
corresponding condition in propagate_necessity() so that only one
instance of strdup would be kept.

Bootstrapped+tested on x86_64-unknown-linux-gnu.
Cross-testing on arm*-*-* and aarch64*-*-* in progress.
OK to commit if testing passes ?

Thanks
Prathamesh