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Date: Sat, 01 Jan 2005 09:32:31 -0700
From: Brian Inglis <Brian DOT Inglis AT SystematicSw DOT ab DOT ca>
Subject: Re: More complaints from tests/libclink/check
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On Sat, 01 Jan 2005 12:57:25 +0200, Eli Zaretskii <eliz AT gnu DOT org>
wrote:

>> Date: Fri, 31 Dec 2004 23:01:02 -0700
>> From: Brian Inglis <Brian DOT Inglis AT SystematicSw DOT ab DOT ca>
>> 
>> >You just define your (POSIX) functions that does the real work, adding
>> >them as stubs to <libc/stubs.h> and letting the C (89 or 99) call them
>> >as necessary.
>> 
>> I am not sure what you mean by stubs here? 
>
>See src/libc/stubs/mkstubs.c.  This program is invoked during the
>library build; it scans the libc/stubs.h header and for each stub
>there produces a stubNN.S file that defines a function which simply
>jmp's to its alias.  Thus, e.g., localtime_r will simply jmp to
>localtime.  The resulting stubNN.S files are then assembled and linked
>into libc.a.
>
>> If the POSIX functions are not declared by including the appropriate
>> header, or by calling them with a local declaration in scope, or if
>> compiler options specify -ansi, we should not pollute the ISO Standard
>> C namespace. 
>
>The stub method solves this problem, as you only get localtime_r
>linked in if you reference it in your program.
>
>The question is, as I wrote elsewhere in this thread, do we want the
>*_r functions as simple aliases for the non-*_r functions, or do we
>really want reentrancy.

The *_r _POSIX_THREAD_SAFE_FUNCTIONS have different interfaces that
support reentrancy/threads by allowing the caller to pass a
buffer/struct pointer instead of using/returning an internal static
buffer/struct. 

The ISO interfaces can just allocate their static buffer/struct and
call the internal _*_r function, whereas the POSIX *_r interface can
be stubbed jumps to the internal _*_r function. 

-- 
Thanks. Take care, Brian Inglis