warning unknown attribute 'no_sanitize' in hb.hh with xlc16/xlclang

[MBaesken]

When building the currently included harfbuzz in OpenJDK on AIX with the latest xlc16/xlclang compiler, we run into this warning :

In file included from /jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-aat-layout.cc:37:
In file included from /jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-aat-layout-kerx-table.hh:31:
/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb-kern.hh:46:3: warning: unknown attribute 'no_sanitize' ignored [-Wunknown-attributes]
HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW
^
/jdk/src/java.desktop/share/native/libfontmanager/harfbuzz/hb.hh:363:63: note: expanded from macro 'HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW'
#define HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW attribute((no_sanitize("signed-integer-overflow")))

Coding : in hb.hh :

#if defined(clang)
/* Disable certain sanitizer errors. /
/ #1247 */
#define HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW attribute((no_sanitize("signed-integer-overflow")))
#else
#define HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW
#endif

I think the “#else” - case of the macro should be used when building with AIX xlc16/xlclang .

[MBaesken]

Small potential patch for the issue

--- a/harfbuzz/hb.hh	Fri Jul 19 12:35:33 2019 +0200
+++ b/harfbuzz/hb.hh	Fri Jul 19 13:19:24 2019 +0200
@@ -357,7 +357,7 @@
 #  define HB_FALLTHROUGH /* FALLTHROUGH */
 #endif
 
-#if defined(__clang__)
+#if defined(__clang__) && !(defined(_AIX) && (defined(__IBMCPP__) || defined(__ibmxl__)))
 /* Disable certain sanitizer errors. */
 /* https://github.com/harfbuzz/harfbuzz/issues/1247 */
 #define HB_NO_SANITIZE_SIGNED_INTEGER_OVERFLOW __attribute__((no_sanitize("signed-integer-overflow")))

[behdad]

Thanks. Given that the compiler involved does seem to impersonate clang, and that this is just a warning, any reason we should fix it instead of just ignoring?

[MBaesken]

Reason is that we want to achieve building the codebase in OpenJDK (including harfbuzz) with "warnings as errors" (we do this already on most other platforms).

[behdad]

I'm glad to hear that the code compiles almost warning-free. Fixed. Thanks.