The #pragma weak directive adds an alternate function name
with weak binding for the function function_name.
>>--#--pragma--weak--(--function_name--,--backup_function_name--)--><
If the definition for the function function_name is not found, the linker resolves the function call to the definition for the function backup_function_name. Otherwise, the linker resolves the function call to the definition for function_name.
If function_name is not referenced, neither function_name nor backup_function_name needs to be declared.
If function_name is referenced, both function_name and backup_function_name must be declared.
Note: Both functions must have full prototypes within the compilation unit. Neither function can be a C++ member function.
In the following example , after the program is linked, the
call to specialization resolves to the definition of
generalization because no definition of specialization exists.
#include <stdio.h>
int generalization(int i) {
printf("in generalization\n");
}
#pragma weak (specialization, generalization)
int main() {
printf("in main\n");
return specialization(6);
}