Please help with __attribute__ weak

[Dimitry Golubovsky <dimitry at golubovsky dot org>]

I need to declare a symbol which is weaker in the executable than in any 
external static or dynamic library.

In other words, the executable provides some fallback function 
implementation (in my example, for "write"). But if the linker or 
dynamic linker resolves it, the symbol definition from an external 
library must be used.

I use:

__f_write_weak_alias(int __fd, __const __ptr_t __buf, size_t __n) 
__attribute__((weak, alias ("write"))); /* alias declaration */

int write(int __fd, __const __ptr_t __buf, size_t __n) {
  printf("Abort\n");
} /* fallback implementation */

But even though "write" is resolved, calling the __f_write_weak_alias 
just prints "Abort" i. e. the symbol "write" was not overridden by the 
library definition.

What is the right way to do this?

Thanks for any advice.

Dimitry Golubovsky
Middletown, CT