diff --git a/libutils/Android.mk b/libutils/Android.mk
index 1c48619..3afc1ec 100644
--- a/libutils/Android.mk
+++ b/libutils/Android.mk
@@ -43,7 +43,7 @@
 	VectorImpl.cpp \
 	misc.cpp
 
-host_commonCflags := -DLIBUTILS_NATIVE=1 $(TOOL_CFLAGS)
+host_commonCflags := -DLIBUTILS_NATIVE=1 $(TOOL_CFLAGS) -Werror
 
 ifeq ($(HOST_OS),windows)
 ifeq ($(strip $(USE_CYGWIN),),)
@@ -99,6 +99,7 @@
 ifeq ($(TARGET_ARCH),mips)
 LOCAL_CFLAGS += -DALIGN_DOUBLE
 endif
+LOCAL_CFLAGS += -Werror
 
 LOCAL_C_INCLUDES += \
 		bionic/libc/private \
@@ -126,7 +127,8 @@
         libbacktrace \
         libcutils \
         libdl \
-        liblog \
+        liblog
+LOCAL_CFLAGS := -Werror
 
 include external/stlport/libstlport.mk
 
diff --git a/libutils/BlobCache.cpp b/libutils/BlobCache.cpp
index 660917b..f00bf14 100644
--- a/libutils/BlobCache.cpp
+++ b/libutils/BlobCache.cpp
@@ -28,7 +28,7 @@
 namespace android {
 
 // BlobCache::Header::mMagicNumber value
-static const uint32_t blobCacheMagic = '_Bb$';
+static const uint32_t blobCacheMagic = ('_' << 24) + ('B' << 16) + ('b' << 8) + '$';
 
 // BlobCache::Header::mBlobCacheVersion value
 static const uint32_t blobCacheVersion = 1;
@@ -49,7 +49,7 @@
     mRandState[1] = (now >> 16) & 0xFFFF;
     mRandState[2] = (now >> 32) & 0xFFFF;
 #endif
-    ALOGV("initializing random seed using %lld", now);
+    ALOGV("initializing random seed using %lld", (unsigned long long)now);
 }
 
 void BlobCache::set(const void* key, size_t keySize, const void* value,
diff --git a/libutils/FileMap.cpp b/libutils/FileMap.cpp
index 933e7aa..be4b14f 100644
--- a/libutils/FileMap.cpp
+++ b/libutils/FileMap.cpp
@@ -23,7 +23,13 @@
 #include <utils/FileMap.h>
 #include <utils/Log.h>
 
+#if defined(HAVE_WIN32_FILEMAP) && !defined(__USE_MINGW_ANSI_STDIO)
+# define PRId32 "I32d"
+# define PRIx32 "I32x"
+# define PRId64 "I64d"
+#else
 #include <inttypes.h>
+#endif
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -169,8 +175,8 @@
             goto try_again;
         }
 
-        ALOGE("mmap(%" PRId64 ",%zu) failed: %s\n",
-            adjOffset, adjLength, strerror(errno));
+        ALOGE("mmap(%lld,%zu) failed: %s\n",
+            (long long)adjOffset, adjLength, strerror(errno));
         return false;
     }
     mBasePtr = ptr;
diff --git a/libutils/LinearAllocator.cpp b/libutils/LinearAllocator.cpp
index a07a291..8b90696 100644
--- a/libutils/LinearAllocator.cpp
+++ b/libutils/LinearAllocator.cpp
@@ -92,7 +92,7 @@
         : mNextPage(0)
     {}
 
-    void* operator new(size_t size, void* buf) { return buf; }
+    void* operator new(size_t /*size*/, void* buf) { return buf; }
 
     void* start() {
         return (void*) (((size_t)this) + sizeof(Page));
@@ -103,7 +103,7 @@
     }
 
 private:
-    Page(const Page& other) {}
+    Page(const Page& /*other*/) {}
     Page* mNextPage;
 };
 
diff --git a/libutils/RefBase.cpp b/libutils/RefBase.cpp
index 385c226..02907ad 100644
--- a/libutils/RefBase.cpp
+++ b/libutils/RefBase.cpp
@@ -17,6 +17,14 @@
 #define LOG_TAG "RefBase"
 // #define LOG_NDEBUG 0
 
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <typeinfo>
+#include <unistd.h>
+
 #include <utils/RefBase.h>
 
 #include <utils/Atomic.h>
@@ -24,13 +32,9 @@
 #include <utils/Log.h>
 #include <utils/threads.h>
 
-#include <stdlib.h>
-#include <stdio.h>
-#include <typeinfo>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <unistd.h>
+#ifndef __unused
+#define __unused __attribute__((__unused__))
+#endif
 
 // compile with refcounting debugging enabled
 #define DEBUG_REFS                      0
@@ -388,7 +392,7 @@
 {
     weakref_impl* const impl = static_cast<weakref_impl*>(this);
     impl->addWeakRef(id);
-    const int32_t c = android_atomic_inc(&impl->mWeak);
+    const int32_t c __unused = android_atomic_inc(&impl->mWeak);
     ALOG_ASSERT(c >= 0, "incWeak called on %p after last weak ref", this);
 }
 
@@ -615,7 +619,7 @@
 {
 }
 
-bool RefBase::onIncStrongAttempted(uint32_t flags, const void* id)
+bool RefBase::onIncStrongAttempted(uint32_t flags, const void* /*id*/)
 {
     return (flags&FIRST_INC_STRONG) ? true : false;
 }
@@ -626,13 +630,15 @@
 
 // ---------------------------------------------------------------------------
 
-void RefBase::renameRefs(size_t n, const ReferenceRenamer& renamer) {
 #if DEBUG_REFS
+void RefBase::renameRefs(size_t n, const ReferenceRenamer& renamer) {
     for (size_t i=0 ; i<n ; i++) {
         renamer(i);
     }
-#endif
 }
+#else
+void RefBase::renameRefs(size_t /*n*/, const ReferenceRenamer& /*renamer*/) { }
+#endif
 
 void RefBase::renameRefId(weakref_type* ref,
         const void* old_id, const void* new_id) {
diff --git a/libutils/StopWatch.cpp b/libutils/StopWatch.cpp
index b1708d6..8c7b596 100644
--- a/libutils/StopWatch.cpp
+++ b/libutils/StopWatch.cpp
@@ -21,7 +21,9 @@
 #include <stdio.h>
 
 /* for PRId64 */
+#ifndef __STDC_FORMAT_MACROS
 #define __STDC_FORMAT_MACROS 1
+#endif
 #include <inttypes.h>
 
 #include <utils/Log.h>
diff --git a/libutils/String16.cpp b/libutils/String16.cpp
index 3bdc349..91efdaa 100644
--- a/libutils/String16.cpp
+++ b/libutils/String16.cpp
@@ -66,8 +66,6 @@
         return getEmptyString();
     }
 
-    const uint8_t* const u8end = u8cur + u8len;
-
     SharedBuffer* buf = SharedBuffer::alloc(sizeof(char16_t)*(u16len+1));
     if (buf) {
         u8cur = (const uint8_t*) u8str;
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index 8acb4d4..49340bb 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -551,7 +551,6 @@
 {
     const char* lastSlash;
     const char* lastDot;
-    int extLen;
     const char* const str = mString;
 
     // only look at the filename
diff --git a/libutils/SystemClock.cpp b/libutils/SystemClock.cpp
index 413250f..dbad581 100644
--- a/libutils/SystemClock.cpp
+++ b/libutils/SystemClock.cpp
@@ -68,13 +68,7 @@
  */
 #define DEBUG_TIMESTAMP         0
 
-static const char *gettime_method_names[] = {
-    "clock_gettime",
-    "ioctl",
-    "systemTime",
-};
-
-#if DEBUG_TIMESTAMP
+#if DEBUG_TIMESTAMP && defined(ARCH_ARM)
 static inline void checkTimeStamps(int64_t timestamp,
                                    int64_t volatile *prevTimestampPtr,
                                    int volatile *prevMethodPtr,
@@ -85,11 +79,16 @@
      * gettid, and int64_t is different on the ARM platform
      * (ie long vs long long).
      */
-#ifdef ARCH_ARM
     int64_t prevTimestamp = *prevTimestampPtr;
     int prevMethod = *prevMethodPtr;
 
     if (timestamp < prevTimestamp) {
+        static const char *gettime_method_names[] = {
+            "clock_gettime",
+            "ioctl",
+            "systemTime",
+        };
+
         ALOGW("time going backwards: prev %lld(%s) vs now %lld(%s), tid=%d",
               prevTimestamp, gettime_method_names[prevMethod],
               timestamp, gettime_method_names[curMethod],
@@ -99,7 +98,6 @@
     // write is interrupted or not observed as a whole.
     *prevTimestampPtr = timestamp;
     *prevMethodPtr = curMethod;
-#endif
 }
 #else
 #define checkTimeStamps(timestamp, prevTimestampPtr, prevMethodPtr, curMethod)
diff --git a/libutils/Threads.cpp b/libutils/Threads.cpp
index ff74914..cc7fe89 100644
--- a/libutils/Threads.cpp
+++ b/libutils/Threads.cpp
@@ -17,16 +17,11 @@
 // #define LOG_NDEBUG 0
 #define LOG_TAG "libutils.threads"
 
-#include <utils/threads.h>
-#include <utils/Log.h>
-
-#include <cutils/sched_policy.h>
-
+#include <assert.h>
+#include <errno.h>
+#include <memory.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <memory.h>
-#include <errno.h>
-#include <assert.h>
 #include <unistd.h>
 
 #if defined(HAVE_PTHREADS)
@@ -47,6 +42,17 @@
 #include <sys/prctl.h>
 #endif
 
+#include <utils/threads.h>
+#include <utils/Log.h>
+
+#include <cutils/sched_policy.h>
+
+#ifdef HAVE_ANDROID_OS
+# define __android_unused
+#else
+# define __android_unused __attribute__((__unused__))
+#endif
+
 /*
  * ===========================================================================
  *      Thread wrappers
@@ -119,7 +125,7 @@
 
 int androidCreateRawThreadEtc(android_thread_func_t entryFunction,
                                void *userData,
-                               const char* threadName,
+                               const char* threadName __android_unused,
                                int32_t threadPriority,
                                size_t threadStackSize,
                                android_thread_id_t *threadId)
@@ -251,9 +257,9 @@
 
 int androidCreateRawThreadEtc(android_thread_func_t fn,
                                void *userData,
-                               const char* threadName,
-                               int32_t threadPriority,
-                               size_t threadStackSize,
+                               const char* /*threadName*/,
+                               int32_t /*threadPriority*/,
+                               size_t /*threadStackSize*/,
                                android_thread_id_t *threadId)
 {
     return doCreateThread(  fn, userData, threadId);
diff --git a/libutils/Timers.cpp b/libutils/Timers.cpp
index a431e92..4687d4d 100644
--- a/libutils/Timers.cpp
+++ b/libutils/Timers.cpp
@@ -32,9 +32,9 @@
 #include <windows.h>
 #endif
 
+#if defined(HAVE_ANDROID_OS)
 nsecs_t systemTime(int clock)
 {
-#if defined(HAVE_ANDROID_OS)
     static const clockid_t clocks[] = {
             CLOCK_REALTIME,
             CLOCK_MONOTONIC,
@@ -46,7 +46,10 @@
     t.tv_sec = t.tv_nsec = 0;
     clock_gettime(clocks[clock], &t);
     return nsecs_t(t.tv_sec)*1000000000LL + t.tv_nsec;
+}
 #else
+nsecs_t systemTime(int /*clock*/)
+{
     // Clock support varies widely across hosts. Mac OS doesn't support
     // posix clocks, older glibcs don't support CLOCK_BOOTTIME and Windows
     // is windows.
@@ -54,8 +57,8 @@
     t.tv_sec = t.tv_usec = 0;
     gettimeofday(&t, NULL);
     return nsecs_t(t.tv_sec)*1000000000LL + nsecs_t(t.tv_usec)*1000LL;
-#endif
 }
+#endif
 
 int toMillisecondTimeoutDelay(nsecs_t referenceTime, nsecs_t timeoutTime)
 {
diff --git a/libutils/Unicode.cpp b/libutils/Unicode.cpp
index a66e3bb..fe8887d 100644
--- a/libutils/Unicode.cpp
+++ b/libutils/Unicode.cpp
@@ -576,7 +576,7 @@
 char16_t* utf8_to_utf16_n(const uint8_t* src, size_t srcLen, char16_t* dst, size_t dstLen) {
     const uint8_t* const u8end = src + srcLen;
     const uint8_t* u8cur = src;
-    const uint16_t* const u16end = dst + dstLen;
+    const char16_t* const u16end = dst + dstLen;
     char16_t* u16cur = dst;
 
     while (u8cur < u8end && u16cur < u16end) {
diff --git a/libutils/tests/BlobCache_test.cpp b/libutils/tests/BlobCache_test.cpp
index 7202123..dac4e2c 100644
--- a/libutils/tests/BlobCache_test.cpp
+++ b/libutils/tests/BlobCache_test.cpp
@@ -44,7 +44,7 @@
 };
 
 TEST_F(BlobCacheTest, CacheSingleValueSucceeds) {
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
     ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 4));
     ASSERT_EQ('e', buf[0]);
@@ -54,7 +54,7 @@
 }
 
 TEST_F(BlobCacheTest, CacheTwoValuesSucceeds) {
-    char buf[2] = { 0xee, 0xee };
+    unsigned char buf[2] = { 0xee, 0xee };
     mBC->set("ab", 2, "cd", 2);
     mBC->set("ef", 2, "gh", 2);
     ASSERT_EQ(size_t(2), mBC->get("ab", 2, buf, 2));
@@ -66,7 +66,7 @@
 }
 
 TEST_F(BlobCacheTest, GetOnlyWritesInsideBounds) {
-    char buf[6] = { 0xee, 0xee, 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[6] = { 0xee, 0xee, 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
     ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf+1, 4));
     ASSERT_EQ(0xee, buf[0]);
@@ -78,7 +78,7 @@
 }
 
 TEST_F(BlobCacheTest, GetOnlyWritesIfBufferIsLargeEnough) {
-    char buf[3] = { 0xee, 0xee, 0xee };
+    unsigned char buf[3] = { 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
     ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 3));
     ASSERT_EQ(0xee, buf[0]);
@@ -92,7 +92,7 @@
 }
 
 TEST_F(BlobCacheTest, MultipleSetsCacheLatestValue) {
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
     mBC->set("abcd", 4, "ijkl", 4);
     ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 4));
@@ -103,7 +103,7 @@
 }
 
 TEST_F(BlobCacheTest, SecondSetKeepsFirstValueIfTooLarge) {
-    char buf[MAX_VALUE_SIZE+1] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[MAX_VALUE_SIZE+1] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
     mBC->set("abcd", 4, buf, MAX_VALUE_SIZE+1);
     ASSERT_EQ(size_t(4), mBC->get("abcd", 4, buf, 4));
@@ -115,7 +115,7 @@
 
 TEST_F(BlobCacheTest, DoesntCacheIfKeyIsTooBig) {
     char key[MAX_KEY_SIZE+1];
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     for (int i = 0; i < MAX_KEY_SIZE+1; i++) {
         key[i] = 'a';
     }
@@ -165,7 +165,7 @@
 
 TEST_F(BlobCacheTest, CacheMaxKeySizeSucceeds) {
     char key[MAX_KEY_SIZE];
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     for (int i = 0; i < MAX_KEY_SIZE; i++) {
         key[i] = 'a';
     }
@@ -214,7 +214,7 @@
 }
 
 TEST_F(BlobCacheTest, CacheMinKeyAndValueSizeSucceeds) {
-    char buf[1] = { 0xee };
+    unsigned char buf[1] = { 0xee };
     mBC->set("x", 1, "y", 1);
     ASSERT_EQ(size_t(1), mBC->get("x", 1, buf, 1));
     ASSERT_EQ('y', buf[0]);
@@ -282,7 +282,7 @@
 };
 
 TEST_F(BlobCacheFlattenTest, FlattenOneValue) {
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
     roundTrip();
     ASSERT_EQ(size_t(4), mBC2->get("abcd", 4, buf, 4));
@@ -348,7 +348,7 @@
 }
 
 TEST_F(BlobCacheFlattenTest, UnflattenCatchesBadMagic) {
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
 
     size_t size = mBC->getFlattenedSize();
@@ -365,7 +365,7 @@
 }
 
 TEST_F(BlobCacheFlattenTest, UnflattenCatchesBadBlobCacheVersion) {
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
 
     size_t size = mBC->getFlattenedSize();
@@ -384,7 +384,7 @@
 }
 
 TEST_F(BlobCacheFlattenTest, UnflattenCatchesBadBlobCacheDeviceVersion) {
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
 
     size_t size = mBC->getFlattenedSize();
@@ -403,7 +403,7 @@
 }
 
 TEST_F(BlobCacheFlattenTest, UnflattenCatchesBufferTooSmall) {
-    char buf[4] = { 0xee, 0xee, 0xee, 0xee };
+    unsigned char buf[4] = { 0xee, 0xee, 0xee, 0xee };
     mBC->set("abcd", 4, "efgh", 4);
 
     size_t size = mBC->getFlattenedSize();