diff --git a/configure.ac b/configure.ac
index ca8b2538d..b8b063fb2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -223,8 +223,8 @@ AC_PROG_LN_S
 #   -Wall                        CC, CXX
 #
 
-PROSPECTIVE_CFLAGS="-Wall -std=c99 -pedantic-errors"
-PROSPECTIVE_CXXFLAGS="-Wall"
+PROSPECTIVE_CFLAGS="-Wall -Wextra -Wshadow -Werror -std=c99 -pedantic-errors"
+PROSPECTIVE_CXXFLAGS="-Wall -Wextra -Wshadow -Werror"
 
 AC_CACHE_CHECK([whether $CC is Clang],
     [nl_cv_clang],
diff --git a/examples/Makefile-cc2538 b/examples/Makefile-cc2538
index b0d78b540..4206c9d5c 100644
--- a/examples/Makefile-cc2538
+++ b/examples/Makefile-cc2538
@@ -54,9 +54,6 @@ COMMONCFLAGS                   := \
     -ffunction-sections           \
     -Os                           \
     -g                            \
-    -Wall                         \
-    -Wextra                       \
-    -Werror                       \
     $(NULL)
 
 CPPFLAGS                       += \
diff --git a/examples/Makefile-posix b/examples/Makefile-posix
index 42eac0f13..fc1fc5fe5 100644
--- a/examples/Makefile-posix
+++ b/examples/Makefile-posix
@@ -44,9 +44,6 @@ BuildJobs                      ?= 99
 COMMONCFLAGS                   := \
     -O1                           \
     -g                            \
-    -Wall                         \
-    -Wextra                       \
-    -Werror                       \
     $(NULL)
 
 CPPFLAGS                       += \
diff --git a/examples/platforms/posix/logging.c b/examples/platforms/posix/logging.c
index 05e3a02e6..912fb7754 100644
--- a/examples/platforms/posix/logging.c
+++ b/examples/platforms/posix/logging.c
@@ -41,21 +41,21 @@
 // Macro to append content to end of the log string.
 
 #define LOG_PRINTF(...)                                                                     \
-    charsWritten = snprintf(&logString[index], sizeof(logString) - index , __VA_ARGS__);    \
-    VerifyOrExit(charsWritten >= 0, logString[index] = 0);                                  \
-    index += (unsigned int)charsWritten;                                    \
-    VerifyOrExit(index < sizeof(logString), logString[sizeof(logString) -1 ] = 0)
+    charsWritten = snprintf(&logString[offset], sizeof(logString) - offset , __VA_ARGS__);    \
+    VerifyOrExit(charsWritten >= 0, logString[offset] = 0);                                  \
+    offset += (unsigned int)charsWritten;                                    \
+    VerifyOrExit(offset < sizeof(logString), logString[sizeof(logString) -1 ] = 0)
 
 void otPlatLog(otLogLevel aLogLevel, otLogRegion aLogRegion, const char *aFormat, ...)
 {
     struct timeval tv;
     char timeString[40];
     char logString[512];
-    unsigned int index;
+    unsigned int offset;
     int charsWritten;
     va_list args;
 
-    index = 0;
+    offset = 0;
 
     gettimeofday(&tv, NULL);
     strftime(timeString, sizeof(timeString), "%Y-%m-%d %H:%M:%S", localtime(&tv.tv_sec));
@@ -129,10 +129,10 @@ void otPlatLog(otLogLevel aLogLevel, otLogRegion aLogRegion, const char *aFormat
     }
 
     va_start(args, aFormat);
-    charsWritten = vsnprintf(&logString[index], sizeof(logString) - index, aFormat, args);
+    charsWritten = vsnprintf(&logString[offset], sizeof(logString) - offset, aFormat, args);
     va_end(args);
 
-    VerifyOrExit(charsWritten >= 0, logString[index] = 0);
+    VerifyOrExit(charsWritten >= 0, logString[offset] = 0);
 
 exit:
     fprintf(stderr, "%s\r", logString);
diff --git a/tests/unit/test_diag.cpp b/tests/unit/test_diag.cpp
index 488c773af..88fd8b367 100644
--- a/tests/unit/test_diag.cpp
+++ b/tests/unit/test_diag.cpp
@@ -143,7 +143,7 @@ void TestDiag()
 
     // initialize platform layer
     int argc = 2;
-    char *argv[2] = {(char *)"test_diag", (char *)"1"};
+    char *argv[8] = {(char *)"test_diag", (char *)"1"};
     PlatformInit(argc, argv);
 
     // initialize diagnostics module
@@ -156,12 +156,11 @@ void TestDiag()
     {
         char string[50];
         int length = strlen(tests[i].command);
-
         char *cmd;
-        char *argv[8];
-        int argc = 0;
         char *output = NULL;
 
+	argc = 0;
+
         memcpy(string, tests[i].command, length + 1);
 
         for (cmd = string + 1; (cmd < string + length) && (cmd != NULL); ++cmd)
diff --git a/tests/unit/test_lowpan.cpp b/tests/unit/test_lowpan.cpp
index 7a03fcccd..f2b392983 100644
--- a/tests/unit/test_lowpan.cpp
+++ b/tests/unit/test_lowpan.cpp
@@ -145,12 +145,12 @@ void TestLowpanIphc(void)
                      "6lo: Lowpan::Decompress failed");
 
         // ===> Test Lowpan::Compress
-        int resultLength = sMockLowpan.Compress(*message, macSource, macDest,
-                                                result);
+        int compressBytes = sMockLowpan.Compress(*message, macSource, macDest,
+                                                 result);
         printf("Compressed OpenThread:\n");
-        otTestPrintHex(result, resultLength);
+        otTestPrintHex(result, compressBytes);
 
-        VerifyOrQuit(memcmp(frame.GetPayload(), result, resultLength) == 0,
+        VerifyOrQuit(memcmp(frame.GetPayload(), result, compressBytes) == 0,
                      "6lo: Lowpan::Compress failed");
 
         SuccessOrQuit(Message::Free(*message), "6lo: Message:Free failed");