[PATCH] D28596: [compiler-rt] General definition for weak functions.

[Marcos Pividori via Phabricator via llvm-commits]

mpividori added a comment.

@kubabrecka @aizatsky  Ok, thanks for your comments.

So, we can't take the same approach for all platforms because: Windows supports "weak aliases" , Linux support weak functions and weak aliases, Darwin support weak functions.
So, we need to continue with this approach:

- Weak functions with default implementation for Linux and Darwin:

  __attribute__ ((weak)) void fun () {
    // Default implementation
  }

- Use an auxiliar function for windows and define a weak alias:

  void fun_def() {
    // Default implementation
  }
  WIN_WEAK_ALIAS(fun, fun__def)

Do you agree on this point? Would you do it differently?

-----------------

So, if we include that code, we have some duplicated code:

  #if ! SANITIZER_WINDOWS
   __attribute__ ((weak)) void fun () {
     // Default implementation
   }
  #else
   void fun_def() {
     // Default implementation
   }
   WIN_WEAK_ALIAS(fun, fun__def)
  #endif

To avoid duplicated code, I will define a macro `WEAK_DEF()`, so we can reduce that code to:

  WEAK_DEF(void, fun, ()) {
     // Default implementation
   }

Would you agree on this point? Would you do it differently?

-----------------

In the headers, I also need to export the default function on Windows ("fun__def").
So, we can use "#ifdef" and declare the functions as:

  SANITIZER_INTERFACE_ATTRIBUTE void fun();
  #ifdef SANITIZER_WINDOWS
  SANITIZER_INTERFACE_ATTRIBUTE void fun__def();
  #endif

To avoid that, I will define a macro `WEAK_INTERFACE_DECL()`, so we can reduce that code to:

  WEAK_INTERFACE_DECL(void, fun, ());

Would you agree on this point? Would you do it differently?

-----------------

As we declare many weak functions in different sanitizers, not only in `sanitizer_common`, I thought it would be appropriate to use the macros that I mention instead of using "#ifdefs".

I would appreciate your comment on this. I really want to finish with these changes to continue focused on libFuzzer.

Thanks.


https://reviews.llvm.org/D28596