El 08/01/2013 17:32, Tim Blechmann escribió:
of course, if the compiler implements std::atomic, there is absolutely no need for boost::atomic in the first place ... the whole point is to provide a compatibility layer to provide c++11-style atomics for old compilers, that don't support c++11 atomics ... which, btw is one of the reason why the original author decided to use inline assembly instead of compiler intrinsics
I have no experience on assembler coding, but porting assembler code from one compiler to another on the same architecture is hard? Looking at boost/smart_ptr/detail/sp_counted_base_xxx.hpp I see that gcc x86 code for atomic_exchange_and_add is: // int r = *pw; // *pw += dv; // return r; __asm__ __volatile__ ( "lock\n\t" "xadd %1, %0": "=m"( *pw ), "=r"( r ): // outputs (%0, %1) "m"( *pw ), "1"( dv ): // inputs (%2, %3 == %1) "memory", "cc" // clobbers ); whereas codewarrior code looks like this: // int r = *pw; // *pw += dv; // return r; asm { mov esi, [pw] mov eax, dv lock xadd dword ptr [esi], eax } Obviously we have "lock" and "xadd" on both cases but we have a lot of additional stuff in the gcc case. If porting between compilers in the same architecture is not very hard, Boost.Atomic already supports most widely used architectures (i386, x86_64, ppc32, ppc64, armv5, armv6, armv7, alpha), then support for more compilers wouldn't be hard to add. On the other hard, if we need to write a very different assembler in each compiler, the work will be much harder. Best, Ion