linux: fix a warning in the process_util unittest

base/process_util_unittest.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #define _CRT_SECURE_NO_WARNINGS
 
 #include <limits>
 
 #include "base/command_line.h"
 #include "base/eintr_wrapper.h"
@@ skipping 397 matching lines @@
 
 TEST_F(OutOfMemoryTest, Pvalloc) {
   ASSERT_DEATH(value_ = pvalloc(test_size_), "");
 }
 
 TEST_F(OutOfMemoryTest, Memalign) {
   ASSERT_DEATH(value_ = memalign(4, test_size_), "");
 }
 
 TEST_F(OutOfMemoryTest, Posix_memalign) {
-  ASSERT_DEATH(posix_memalign(&value_, 8, test_size_), "");
+  // Grab the return value of posix_memalign to silence a compiler
+  // warning about unused variables.  We don't actually care about
+  // the return value, since we're asserting death.
+  int ret;
+  ASSERT_DEATH(ret = posix_memalign(&value_, 8, test_size_), "");
 }
 
 extern "C" {
 
 void* __libc_malloc(size_t size);
 void* __libc_realloc(void* ptr, size_t size);
 void* __libc_calloc(size_t nmemb, size_t size);
 void* __libc_valloc(size_t size);
 void* __libc_pvalloc(size_t size);
 void* __libc_memalign(size_t alignment, size_t size);
@@ skipping 20 matching lines @@
   ASSERT_DEATH(value_ = __libc_pvalloc(test_size_), "");
 }
 
 TEST_F(OutOfMemoryTest, __libc_memalign) {
   ASSERT_DEATH(value_ = __libc_memalign(4, test_size_), "");
 }
 
 #endif  // defined(OS_LINUX)
 
 }  // namespace base