Re: FreeBSD/i386 thread test

Bruce Momjian wrote:
> Manfred Spraul wrote:
> > Jeroen Ruigrok/asmodai wrote:
> > 
> > >-On [20030908 23:52], Peter Eisentraut (peter_e@gmx.net) wrote:
> > >  
> > >
> > >>Why would FreeBSD have a "library of thread-safe libc functions" (libc_r)
> > >>if the functions weren't thread-safe?  I think the test is faulty.
> > >>    
> > >>
> > A thread-safe library has a per-thread errno value (i.e. errno is a 
> > #define to a function call), thread-safe io buffers for stdio, etc. Some 
> > of these changes cause a noticable overhead, thus a seperate library for 
> > those users who want to avoid that overhead.
> > 
> > Reentrancy is independant from _r: If you look at the prototype of 
> > gethostbyname(), it's just not possible to make that thread safe with 
> > reasonable effort - the C library would have to keep one buffer per 
> > thread around.
> 
> See the top of src/port/thread.c --- that's exactly what is does (keep
> one buffer per thread around).
> 
>  *  Threading sometimes requires specially-named versions of functions
>  *  that return data in static buffers, like strerror_r() instead of
>  *  strerror().  Other operating systems use pthread_setspecific()
>  *  and pthread_getspecific() internally to allow standard library
>  *  functions to return static data to threaded applications.

And that's exactly what src/tools/test_thread_funcs.c tests for.
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