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Date: Thu, 11 Aug 2011 14:16:11 +0200
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Subject: Re: [Qemu-devel] [PATCH] tcg: Reload local variables after return
	from longjmp
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Blue Swirl <blauwirbel@gmail.com>, TeLeMan <geleman@gmail.com>, Jan Kiszka <jan.kiszka@web.de>, qemu-devel <qemu-devel@nongnu.org>, David Gilbert <david.gilbert@linaro.org>

On 08/11/2011 01:30 PM, Peter Maydell wrote:
>> >  Recent compilers look deep into cpu_exec, find longjmp as a noreturn
>> >  function and decide to smash some stack variables as they won't be used
>> >  again. This may lead to env becoming invalid after return from setjmp,
>> >  causing crashes. Fix it by reloading env from cpu_single_env in that
>> >  case.
> Can you give more details of what compiler/platform this was
> a problem for? My reading of the C standard is that the compiler
> isn't allowed to trash env across this longjmp, because it's
> a variable of automatic scope which isn't modified between the
> setjmp and the longjmp...

longjmp can destroy any non-volatile variable (-Wclobbered warns about 
this).

Paolo