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Re: OpenBSD pch, take 2

From: Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>
To: espie at nerim dot net, GCC Development <gcc at gcc dot gnu dot org>
Date: Mon, 31 Jan 2005 15:47:56 +0100
Subject: Re: OpenBSD pch, take 2
References: <20050131121547.GA24600@tetto.home>

The very nasty thing is that they will *appear* to work. Namely, loading
a pch file will work 95% of the time... and fail whenever the file cannot
be mmaped at the same address due to randomization issues.
So, mark them as completely unreliable.

You may want to find the largest VMA and make the PCH reside in the 200 MB in the middle of it, or allocate the topmost free 200 MB in the address space, etc.

Linux has similar problems, see host-linux.c. If you bring the percentage up to 99% or so, it can be ok because PCH should only cause a compilation slowdown rather than incorrect results.

Paolo

Follow-Ups:
- Re: OpenBSD pch, take 2
  - From: Marc Espie

References:
- OpenBSD pch, take 2
  - From: Marc Espie

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