Define MEMORY_SANITIZER when appropriate.

gpshead · gpshead · commit dcf57d416742 · 2018-11-11T23:15:44.000-08:00
This allows code to easily take conditional action when in an msan
build.  Usually used for telling msan things it can't otherwise
figure out such as syscall, asm behavior, or about libc functions
it isn't yet aware of.
diff --git a/Include/Python.h b/Include/Python.h
@@ -53,6 +53,15 @@
 #include "pyport.h"
 #include "pymacro.h"
 
+/* A convenient way for code to know if clang's memory sanitizer is enabled. */
+#if defined(__has_feature)
+#  if __has_feature(memory_sanitizer)
+#    if !defined(MEMORY_SANITIZER)
+#      define MEMORY_SANITIZER
+#    endif
+#  endif
+#endif
+
 /* Debug-mode build with pymalloc implies PYMALLOC_DEBUG.
  *  PYMALLOC_DEBUG is in error if pymalloc is not in use.
  */
