General definition for weak functions

In this diff, I define a general macro for defining weak functions
with a default implementation: "SANITIZER_INTERFACE_WEAK_DEF()".
This way, we simplify the implementation for different platforms.

For example, we cannot define weak functions on Windows, but we can
use linker pragmas to create an alias to a default implementation.
All of these implementation details are hidden in the new macro.

Also, as I modify the name for exported weak symbols on Windows, I
needed to temporarily disable "dll_host" test for asan, which checks
the list of functions included in asan_win_dll_thunk.

Differential Revision: https://reviews.llvm.org/D28596

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@293419 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 8 deletions

diff --git a/lib/sanitizer_common/sanitizer_printf.cc b/lib/sanitizer_common/sanitizer_printf.cc
index c8317be60..99b7ff1b5 100644
--- a/lib/sanitizer_common/sanitizer_printf.cc
+++ b/lib/sanitizer_common/sanitizer_printf.cc
@@ -214,15 +214,11 @@ void SetPrintfAndReportCallback(void (*callback)(const char *)) {
 }
 
 // Can be overriden in frontend.
-#if SANITIZER_SUPPORTS_WEAK_HOOKS
-SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
-void OnPrint(const char *str) {
-  (void)str;
-}
-#elif SANITIZER_GO && defined(TSAN_EXTERNAL_HOOKS)
-void OnPrint(const char *str);
+#if SANITIZER_GO && defined(TSAN_EXTERNAL_HOOKS)
+// Implementation must be defined in frontend.
+extern "C" void OnPrint(const char *str);
 #else
-void OnPrint(const char *str) {
+SANITIZER_INTERFACE_WEAK_DEF(void, OnPrint, const char *str) {
   (void)str;
 }
 #endif