Re: [committed] correct strcmp() == 0 result for unknown strings (PR 92157)

[Jeff Law <law at redhat dot com>]

On 10/18/19 4:27 PM, Martin Sebor wrote:
> The optimization to fold (strcmp() == 0) results involving
> arrays/strings of unequal size/length has a bug where it is
> unprepared for the compute_string_length() function to return
> an invalid length as an indication that the length is unknown.
> This leads to some strings that are unequal being considered
> equal.
> 
> The attached patch corrects this handling.  I have committed
> it in r277194 with Jeff's okay.
And just for the record, this was caught by the Fedora tester I spoke
about at Cauldron.  I'm spinning the entire distro against our weekly
snapshots again.

Most of the issues have been package level problems (missing #includes,
narrowing conversions, fortran argument passing, assumptions about the
inliner, etc).   Those are largely under control, leading to...

My focus now is on chasing down the codegen issues and I've contacted a
few folks already with problems in their code.  There'll certainly be
more over time.  I'm starting with the easier to understand problems in
the hopes the tough ones (python & perl interpreters) get fixed along
the way.

The nastiest problem so far is the improved tail call opts from Jakub in
May.  AFAICT they're doing the right thing in the caller which is a good
indication that something is going wrong in the indirect sibling callee
(ugh).

jeff