GCC-4 compiler bug

Stanislav Sedov stas at FreeBSD.org
Sat Dec 8 16:21:53 PST 2007

On Wed, Nov 28, 2007 at 02:51:35PM -0800 Matthew Dillon mentioned:
>     Yah, it sounds like we need to get GCC updated.  Would someone like to
>     take on that task?  We have about a month and a half to both do and
>     test a compiler upgrade.
>     I was rather surprised that the compiler barfed on that code.  That code
>     was, in fact, explicitly testing for an overflow.  Regardless of what
>     C99 says, it would be ultra stupid for any compiler to stray outside of
>     the type's width.

Beware, I'll decide to update gcc. We have recently discovered a yet one problem
in gcc 4.2: it brokes code with -O2 optimization level and strict-aliasing
turned on (default).

See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32328 for more details.
Unfortunately, there's no fix for 4.2, and it seems it'd be hard to produce.
Furthermore, it's not clean will you be able to update to 4.3, or not, since
it's under GPL3.

For me, it looks like 4.2.1 was more clean release, than 4.2. So probably
it would be better to just steal patches from 4.2 branch for now.

Stanislav Sedov

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