#pragma redefine_extname old_extname new_extname
This pragma causes every externally defined occurrence of the name old_extname in the object code to be replaced by new_extname. As a result, the linker sees the name new_extname only at link time. If #pragma redefine_extname is encountered after the first use of old_extname, as a function definition, an initializer, or an expression, the effect is undefined. (This pragma is not supported in– Xs mode.)
When #pragma redefine_extname is available, the compiler provides a definition of the predefined macro __PRAGMA_REDEFINE_EXTNAME, which you can use to write portable code that works both with and without #pragma redefine_extname.
#pragma redefine_extname provides an efficient means of redefining a function interface when the name of the function cannot be changed. For example, if the original function definition must be maintained in a library for compatibility with existing programs along with a new definition of the same function for use by new programs, you can add the new function definition to the library by a new name. Subsequently, the header file that declares the function uses #pragma redefine_extname so that all of the uses of the function are linked with the new definition of that function.
#if defined(__STDC__)
#ifdef __PRAGMA_REDEFINE_EXTNAME
extern int myroutine(const long *, int *);
#pragma redefine_extname myroutine __fixed_myroutine
#else /* __PRAGMA_REDEFINE_EXTNAME */
static int
myroutine(const long * arg1, int * arg2)
{
extern int __myroutine(const long *, int*);
return (__myroutine(arg1, arg2));
}
#endif /* __PRAGMA_REDEFINE_EXTNAME */
#else /* __STDC__ */
#ifdef __PRAGMA_REDEFINE_EXTNAME
extern int myroutine();
#pragma redefine_extname myroutine __fixed_myroutine
#else /* __PRAGMA_REDEFINE_EXTNAME */
static int
myroutine(arg1, arg2)
long *arg1;
int *arg2;
{
extern int __fixed_myroutine();
return (__fixed_myroutine(arg1, arg2));
}
#endif /* __PRAGMA_REDEFINE_EXTNAME */
#endif /* __STDC__ */