Re: PATCH: Initialize tmp_obstack

[Daniel Jacobowitz <drow@false.org>]

On Tue, Dec 05, 2006 at 10:48:40PM +0100, Mark Kettenis wrote:
> Sorry, yes, this was meant to go to the list.  My proposal is not to "fix"
> this at all.  It's a GCC bug, that's presumably fixed, and we'll ship
> with -Werror turned off by default anyway.

Well, there seem to be enough systems with affected GCC that HJ, Jim,
and I all hit it - Ubuntu Edgy is one such.

We could discuss this till we're blue in the face without getting
anywhere; the uninitialized warnings are not reliable in face of this
sort of pattern (isn't it a classical example of why uninitialized
warnings are hard?).

I think we're being overly optimistic if we expect GCC to get it right
all the time.  In fact, I asked a bunch of GCC developers about it on
IRC and the best response I got was "then you are screwed".  Or Diego's
explanation:

> We don't explicitly try to handle it.  it's mostly side-effect of
> various optimizations.  some times it's jump-threading, others it's
> PRE, others it's CCP, others it's VRP.

> that irritates the hell out of me.  we depend on optimizations for
> this warning.

I know that's a widely held position.

-- 
Daniel Jacobowitz
CodeSourcery