Prevent an implicit int promotion in malloc/tst-alloc_buffer.c

According to ISO C11, section 6.5.3.3 "Unary arithmetic operators", the
result of the ~ operator is the bitwise complement of its (promoted)
operand.
This can lead to a comparison of a char with another integer type.

Tested on powerpc, powerpc64 and powerpc64le.

	* malloc/tst-alloc_buffer.c (test_misaligned): Cast to char
	before comparing with another char.

2 files changed, 6 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index b213e7c493..9e19f62d9d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-06-26  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
+
+	* malloc/tst-alloc_buffer.c (test_misaligned): Cast to char
+	before comparing with another char.
+
 2017-06-25  Rical Jasan  <ricaljasan@pacific.net>
 
 	* manual/math.texi: Fix a grammatical error.
diff --git a/malloc/tst-alloc_buffer.c b/malloc/tst-alloc_buffer.c
index 1c143999c7..9b2bd2046a 100644
--- a/malloc/tst-alloc_buffer.c
+++ b/malloc/tst-alloc_buffer.c
@@ -429,7 +429,7 @@ test_misaligned (char pad)
   }
 
   /* Verify that padding was not overwritten.  */
-  TEST_VERIFY (backing[0] == ~pad);
+  TEST_VERIFY (backing[0] == (char) ~pad);
   TEST_VERIFY (backing[SIZE + 1] == pad);
   free (backing);
 }