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List:       pcc-list
Subject:    Re: Correct way to redirect functions at asm level?
From:       Gregory McGarry <greg () bitlynx ! com>
Date:       2009-08-24 21:25:29
Message-ID: 2B2839F7-3891-433E-B0B3-DD452A3671DD () bitlynx ! com
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On 25/08/2009, at 1:07 AM, Detlef Riekenberg wrote:

> glibc does a redirection for several c functions at the asm level.
> (lstat, pread, pwrite as examples).
>
> I added "defined __PCC__" to the Macro definition <sys/cdefs.h>
>
> Is this the correct way to do that?
>
> -------- part of sys/cdefs.h --
> /* __asm__ ("xyz") is used throughout the headers to rename functions
>    at the assembly language level.  This is wrapped by the __REDIRECT
>    macro, in order to support compilers that can do this some other
>    way.  When compilers don't support asm-names at all, we have to do
>    preprocessor tricks instead (which don't have exactly the right
>    semantics, but it's the best we can do).
>
>    Example:
>    int __REDIRECT(setpgrp, (__pid_t pid, __pid_t pgrp), setpgid); */
>
> #if defined __PCC__ || (defined __GNUC__ && __GNUC__ >= 2)
>
> # define __REDIRECT(name, proto, alias) name proto __asm__ (__ASMNAME
> (#alias))
> # ifdef __cplusplus
> #  define __REDIRECT_NTH(name, proto, alias) \
>      name proto __THROW __asm__ (__ASMNAME (#alias))
> # else
> #  define __REDIRECT_NTH(name, proto, alias) \
>      name proto __asm__ (__ASMNAME (#alias)) __THROW
> # endif
> # define __ASMNAME(cname)  __ASMNAME2 (__USER_LABEL_PREFIX__, cname)
> # define __ASMNAME2(prefix, cname) __STRING (prefix) cname
>
> /*
> #elif __SOME_OTHER_COMPILER__
>
> # define __REDIRECT(name, proto, alias) name proto; \
> 	_Pragma("let " #name " = " #alias)
> */
> #endif
> ------------------------------

I believe that should work.  The OSX headers and mingw sources do the  
same thing.

#if __DARWIN_UNIX03 && !defined(__LP64__)
#define __DARWIN_ALIAS(sym) __asm("_" __STRING(sym) "$UNIX2003")
#else
#define __DARWIN_ALIAS(sym)
#endif


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