[Bug sanitizer/109882] sanitizer/common_interface_defs.h bogusly defines __has_feature

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109882

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Libstdc++ itself does this:

#if __SANITIZE_THREAD__
#  define _GLIBCXX_TSAN 1
#elif defined __has_feature
# if __has_feature(thread_sanitizer)
#  define _GLIBCXX_TSAN 1
# endif
#endif

The sanitizers could do something similar, although it looks like they don't
actually need to. The only use of __has_feature in the public API is in
asan_interface.h and that could easily be replaced. Then __has_feature can be
redefined in the internal headers, which (I assume) aren't meant to be included
by user code.

Something like this (untested):

diff --git a/libsanitizer/include/sanitizer/asan_interface.h
b/libsanitizer/include/sanitizer/asan_interface.h
index 9bff21c117b..186269ad694 100644
--- a/libsanitizer/include/sanitizer/asan_interface.h
+++ b/libsanitizer/include/sanitizer/asan_interface.h
@@ -48,7 +48,15 @@ void __asan_poison_memory_region(void const volatile *addr,
size_t size);
 void __asan_unpoison_memory_region(void const volatile *addr, size_t size);

 // Macros provided for convenience.
-#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+#ifdef __has_feature
+#if __has_feature(address_sanitizer)
+#define ASAN_DEFINE_REGION_MACROS
+#endif
+#elif defined(__SANITIZE_ADDRESS__)
+#define ASAN_DEFINE_REGION_MACROS
+#endif
+
+#ifdef ASAN_DEFINE_REGION_MACROS
 /// Marks a memory region as unaddressable.
 ///
 /// \note Macro provided for convenience; defined as a no-op if ASan is not
@@ -74,6 +82,7 @@ void __asan_unpoison_memory_region(void const volatile *addr,
size_t size);
 #define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
   ((void)(addr), (void)(size))
 #endif
+#undef ASAN_DEFINE_REGION_MACROS

 /// Checks if an address is poisoned.
 ///
diff --git a/libsanitizer/include/sanitizer/common_interface_defs.h
b/libsanitizer/include/sanitizer/common_interface_defs.h
index 2f415bd9e85..2f9c83ef74e 100644
--- a/libsanitizer/include/sanitizer/common_interface_defs.h
+++ b/libsanitizer/include/sanitizer/common_interface_defs.h
@@ -15,11 +15,6 @@
 #include <stddef.h>
 #include <stdint.h>

-// GCC does not understand __has_feature.
-#if !defined(__has_feature)
-#define __has_feature(x) 0
-#endif
-
 #ifdef __cplusplus
 extern "C" {
 #endif
diff --git a/libsanitizer/sanitizer_common/sanitizer_internal_defs.h
b/libsanitizer/sanitizer_common/sanitizer_internal_defs.h
index 98186c429e9..7574dce7f4a 100644
--- a/libsanitizer/sanitizer_common/sanitizer_internal_defs.h
+++ b/libsanitizer/sanitizer_common/sanitizer_internal_defs.h
@@ -14,6 +14,11 @@

 #include "sanitizer_platform.h"

+// GCC does not understand __has_feature.
+#if !defined(__has_feature)
+#define __has_feature(x) 0
+#endif
+
 #ifndef SANITIZER_DEBUG
 # define SANITIZER_DEBUG 0
 #endif