On Tue, Feb 20, 2018 at 01:13:13PM -0700, Martin Sebor wrote:
> A safer and even more conservative alternative that should be
> equivalent to your approach while avoiding the sprintf regressions
> is to add another mode to the function and have it clear *minlen
> as an option.  This lets the strlen code obtain the conservative
> lower bound without compromising the sprintf warnings.

I fail to see what it would be good for to set *MINLEN to zero and
*MAXLEN to all ones for the non-warning use cases, we simply don't know
anything about it, both NULL_TREEs i.e. returning false is better.  I'm
offering two alternate patches which use
fuzzy == 0 for the previous !fuzzy, fuzzy == 1 for conservatively correct
code that assumes strlen can't cross field/variable boundaries in
compliant programs and fuzzy == 2 which does that + whatever the warning
code wants.  Additionally, I've rewritten the COND_EXPR handling, so that
it matches exactly the PHI handling.

The first patch doesn't change the 2 argument get_range_strlen and changes
gimple_fold_builtin_strlen to use the 6 argument one, the second patch
changes also the 2 argument get_range_strlen similarly to what you've done
in your patch.

Tested on x86_64-linux and i686-linux, ok for trunk if it passes
bootstrap/regtest?  Which one?

	Jakub