blog/2021-04-25-weak-symbol

[giscus[bot]]

blog/2021-04-25-weak-symbol

Updated in 2023-10. C/C++ GCC and Clang support attribute((weak)) which marks a symbol weak. The same effect can be achieved with a preprocessor directive #pragma weak symbol. Object file format I

https://maskray.me/blog/2021-04-25-weak-symbol

[ghost]

Under the section Mach-O:

A weak definition in the executable takes precedence over a strong definition in a dylib. [...]

Perhaps this sentence could be clarified by noting that a weak definition in the executable does not override a strong definition in a dylib when the symbol is used within the dylib itself. For example:

// shared.c
#include <stdio.h>
void f(void) { puts(__FILE_NAME__); }
void g(void) { f(); }

// main.c
#include <stdio.h>
[[gnu::weak]] void f(void) { puts(__FILE_NAME__); }
void g(void);
int main(void) {
  f(); // prints "main.c"
  g(); // prints "shared.c"
  return 0;
}

[MaskRay]

Thanks for the example! Incorporated