On Sun, 2007-10-21 at 20:16 +0400, Tomash Brechko wrote: > But if C99 is thread-neutral, then it's compiler's responsibility to > ensure the same result as some abstract machine
No. The compiler is responsible for ensuring that things work if, and only if: 1. your program conforms in required ways 2. you only call functions in the standard library or functions you define in your program Therefore, when making calls to ANY external library, all bets are off UNLESS that library also meets the above conditions. Interfacing the operating system in any way OTHER than the C standard library functions immediately relieves the compiler of all responsibility -- and that includes calls to Posix functions which are not implemented entirely in Standard C. Of course, a C compiler may make additional guarantees, for example, Posix compliance, but then you must check the Posix standard to see what additional things it promises. AFAIK, access to a shared variable is sound if serialised by a mutex. However that isn't a proper description, there are situations where you can safely read a shared variable without a lock being held, for example if you know another thread has not modified it since the last synchronisation. -- John Skaller <skaller at users dot sf dot net> Felix, successor to C++: http://felix.sf.net
