[patch][gold] Avoid invalid unaligned write

[Rafael EspÃndola <rafael dot espindola at gmail dot com>]

A simple testcase with just

movl $foo, %edi
foo:

will cause an unaligned access in gold. A backtrace found with
-fsanitize=alignment is attached.

The attached patch avoids the unaligned access.

Cheers,
Rafael

2015-06-07  Rafael Ãvila de EspÃndola  <rafael.espindola@gmail.com>

* elfcpp_swap.h (Swap::writeval): Avoid unaligned access.

Attachment: trace
Description: Binary data

diff --git a/elfcpp/elfcpp_swap.h b/elfcpp/elfcpp_swap.h
index 5b9a915..cddc0b3 100644
--- a/elfcpp/elfcpp_swap.h
+++ b/elfcpp/elfcpp_swap.h
@@ -234,7 +234,10 @@ struct Swap
 
   static inline void
   writeval(Valtype* wv, Valtype v)
-  { *wv = Convert<size, big_endian>::convert_host(v); }
+  {
+    Valtype T = Convert<size, big_endian>::convert_host(v);
+    memcpy(wv, &T, sizeof(T));
+  }
 
   static inline Valtype
   readval(const unsigned char* wv)