Re: gcc4 vs gcc3: a case (kerTeX)

[Chuck Swiger <cswiger%mac.com@localhost>]

On Mar 9, 2011, at 11:50 AM, tlaronde%polynum.com@localhost wrote:
>> Does "-O2 -fno-strict-aliasing" work better?
>> 
>> C99's type-punning assumptions (implied by -O2 in gcc-4.x including 
>> -fstrict-aliasing) aren't safe with older code which worked fine with prior 
>> versions of the compiler.
> 
> Thanks for the tip, but in this case no: it doesn't work.

OK.  Too bad, but it was the most likely candidate and worth a try.

If you wanted to triage the issue more carefully, you'd need to enable the 
various suboptions which are enabled by -O2 which are not in -O1 and figure out 
which one(s) are responsible.

On Mar 9, 2011, at 11:53 AM, Martin Husemann wrote:
> Well, I wouldn't bet on it, but so far, every time something like this
> came up, it ended with gcc being correct and the C code violating the
> standard in some subtle way.

Um, there are ~700+ open bug reports listed here:

http://gcc.gnu.org/bugzilla/buglist.cgi?product=gcc&component=rtl-optimization&resolution=---
http://gcc.gnu.org/bugzilla/buglist.cgi?product=gcc&component=tree-optimization&resolution=---

Remove "&resolution=---" (and be prepared to wait), and there are many 
thousands of bugs which have been closed....

Regards,
-- 
-Chuck