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pthreads and standard C library calls and maybe magic Xcode switches
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pthreads and standard C library calls and maybe magic Xcode switches


  • Subject: pthreads and standard C library calls and maybe magic Xcode switches
  • From: Cem Karan <email@hidden>
  • Date: Tue, 21 Aug 2007 16:14:02 -0400

I'm continuing to work on my pthreads based program, and realized that I've run into a potential problem. When I access memory that is shared between two threads, I always mark the memory as volatile, and I use a lock around it. This works for my own code, but what about code that is coming in from the standard libraries, like memcpy()? I can put locks around it all day, but that doesn't make memcpy() have volatile qualified arguments, which means that there may be caching going on that makes a copy done by one thread on one processor invisible to a thread on another processor (that is what the volatile is for) despite locking. I'm quite willing to write wrappers like that below where needed, but my question is, is there a thread-aware version of the standard C library? If so, how do I tell Xcode to use it? Better yet, is there a magic switch somewhere that I can throw that will tell Xcode to be aware that my code is threaded, and that therefore all the caches must be kept fully coherent between the cores/processors?

inline volatile void *memcpy(volatile void *dest, volatile void *source, size_t len)
{
return memcpy(dest, source, len);
}


Thanks,
Cem Karan
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