[patch 4/4] -fstrict-volatile-bitfields cleanup v3: remove from defaults on all targets
Joseph S. Myers
joseph@codesourcery.com
Mon Sep 2 16:05:00 GMT 2013
On Mon, 2 Sep 2013, Richard Earnshaw wrote:
> On 01/09/13 14:10, Bernd Edlinger wrote:
> > IMHO the AAPCS forbids packed structures. Therefore we need not
> > interfere with the C++ memory model if we have unaligned data.
>
> The AAPCS neither forbids nor requires packed structures. They're a GNU
> extension and as such not part of standard C++. Thus the semantics of
> such an operation are irrelavant to the AAPCS: you get to chose what the
> behaviour is in this case...
The trouble is that AAPCS semantics are incompatible with the default GNU
semantics for non-packed structures as well - AAPCS
strict-volatile-bitfields is only compatible with --param
allow-store-data-races=1, which is not the default for any language
variant accepted by GCC (and I say that the default language semantics
here should not depend on the target architecture).
--
Joseph S. Myers
joseph@codesourcery.com
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