Switch to memcpy for accessing misaligned data.

Bug: http://b/31532493

Using misaligned pointers forces us to potentially take the address of
members in a packed structure (which is now a warning/error in the
latest Clang). Using memcpy() is the proper way to handle this kind of
problem, as the compiler can insert the proper instructions (and usually
elide the memcpy() entirely).

Test: Built correctly with updated compilers.
Change-Id: Ia1f6eb62cf19404ff76b71d3c6c7ffffa1403120

1 files changed, 7 insertions, 13 deletions

diff --git a/base/include/android-base/memory.h b/base/include/android-base/memory.h
index 3a2f8fad6..997122623 100644
--- a/base/include/android-base/memory.h
+++ b/base/include/android-base/memory.h
@@ -20,25 +20,19 @@
 namespace android {
 namespace base {
 
-// Use packed structures for access to unaligned data on targets with alignment
+// Use memcpy for access to unaligned data on targets with alignment
 // restrictions.  The compiler will generate appropriate code to access these
 // structures without generating alignment exceptions.
 template <typename T>
-static inline T get_unaligned(const T* address) {
-  struct unaligned {
-    T v;
-  } __attribute__((packed));
-  const unaligned* p = reinterpret_cast<const unaligned*>(address);
-  return p->v;
+static inline T get_unaligned(const void* address) {
+  T result;
+  memcpy(&result, address, sizeof(T));
+  return result;
 }
 
 template <typename T>
-static inline void put_unaligned(T* address, T v) {
-  struct unaligned {
-    T v;
-  } __attribute__((packed));
-  unaligned* p = reinterpret_cast<unaligned*>(address);
-  p->v = v;
+static inline void put_unaligned(void* address, T v) {
+  memcpy(address, &v, sizeof(T));
 }
 
 } // namespace base