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 jos...@codesourcery.com
