[PATCH] avoid using strnlen result for late calls to strlen (PR 82604)

[Jeff Law]

On 06/18/2018 01:15 PM, Martin Sebor wrote:
> While looking into opportunities to detect strnlen/strlen coding
> mistakes (pr86199) I noticed a bug in the strnlen implementation
> I committed earlier today that lets a strnlen() result be saved
> and used in subsequent calls to strlen() with the same argument.
> The attached patch changes the handle_builtin_strlen() function
> to discard the strnlen() result unless its bound is greater than
> the length of the string.
> 
> Martin
> 
> gcc-86204.diff
> 
> 
> PR tree-optimization/86204 -  wrong strlen result after prior strnlen
> 
> gcc/ChangeLog:
> 
> 	PR tree-optimization/86204
> 	* tree-ssa-strlen.c (handle_builtin_strlen): Avoid storing
> 	a strnlen result if it's less than the length of the string.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR tree-optimization/86204
> 	* gcc.dg/strlenopt-46.c: New test.
OK.  Though I must admit I don't like having variables "bounded" and
"bound" in the same function.  So consider renaming one to avoid future
confusion.

jeff