Messages in this thread |  | | From | (Linus Torvalds) | Subject | Re: Invalid compilation without -fno-strict-aliasing | Date | Wed, 26 Feb 2003 17:26:37 +0000 (UTC) |
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In article <20030225234646.GB30611@bougret.hpl.hp.com>, Jean Tourrilhes <jt@bougret.hpl.hp.com> wrote: > > It looks like a compiler bug to me...
Why do you think the kernel uses "-fno-strict-aliasing"?
The gcc people are more interested in trying to find out what can be allowed by the c99 specs than about making things actually _work_. The aliasing code in particular is not even worth enabling, it's just not possible to sanely tell gcc when some things can alias.
> Some users have complained that when the following code is >compiled without the -fno-strict-aliasing, the order of the write and >memcpy is inverted (which mean a bogus len is mem-copied into the >stream).
The "problem" is that we inline the memcpy(), at which point gcc won't care about the fact that it can alias, so they'll just re-order everything and claim it's out own fault. Even though there is no sane way for us to even tell gcc about it.
I tried to get a sane way a few years ago, and the gcc developers really didn't care about the real world in this area. I'd be surprised if that had changed, judging by the replies I have already seen.
I'm not going to bother to fight it.
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