Re: FreeBSD/i386 thread test

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.

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