From 369e264e2ee07cd30188e24e12673a24d1c52dcc Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Mon, 9 May 2016 22:55:21 -0700
Subject: [PATCH] dsp.h: add WEBP_UBSAN_IGNORE_UNDEF

only defined when WEBP_FORCE_ALIGNED isn't. use it to quiet alignment
warnings VP8LoadNewBytes().

Change-Id: I710a74bb9375285974e97022540551a3f4eda414
---
 src/dsp/dsp.h              | 13 +++++++++++++
 src/utils/bit_reader_inl.h |  3 ++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/dsp/dsp.h b/src/dsp/dsp.h
index 10c16ee4..f09d7cdd 100644
--- a/src/dsp/dsp.h
+++ b/src/dsp/dsp.h
@@ -101,6 +101,19 @@ extern "C" {
 #endif
 #endif
 
+// This macro prevents the undefined behavior sanitizer from reporting
+// failures. This is only meant to silence unaligned loads on platforms that
+// are known to support them.
+#define WEBP_UBSAN_IGNORE_UNDEF
+#if !defined(WEBP_FORCE_ALIGNED) && defined(__clang__) && \
+    defined(__has_attribute)
+#if __has_attribute(no_sanitize)
+#undef WEBP_UBSAN_IGNORE_UNDEF
+#define WEBP_UBSAN_IGNORE_UNDEF \
+  __attribute__((no_sanitize("undefined")))
+#endif
+#endif
+
 typedef enum {
   kSSE2,
   kSSE3,
diff --git a/src/utils/bit_reader_inl.h b/src/utils/bit_reader_inl.h
index 37215702..99ed3137 100644
--- a/src/utils/bit_reader_inl.h
+++ b/src/utils/bit_reader_inl.h
@@ -55,7 +55,8 @@ void VP8LoadFinalBytes(VP8BitReader* const br);
 // Inlined critical functions
 
 // makes sure br->value_ has at least BITS bits worth of data
-static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
+static WEBP_UBSAN_IGNORE_UNDEF WEBP_INLINE
+void VP8LoadNewBytes(VP8BitReader* const br) {
   assert(br != NULL && br->buf_ != NULL);
   // Read 'BITS' bits at a time if possible.
   if (br->buf_ < br->buf_max_) {