diff --git a/.github/workflows/android.yml b/.github/workflows/android.yml
index 859824e03..e5f8c2e01 100644
--- a/.github/workflows/android.yml
+++ b/.github/workflows/android.yml
@@ -31,7 +31,7 @@ jobs:
 
       - name: Configure
         env:
-          CXXFLAGS: -Wall -Wextra -Wpedantic -Wsign-conversion -Wtautological-compare -Werror ${{env.CXXFLAGS}}
+          CXXFLAGS: -Wall -Wextra -Wpedantic -Wsign-conversion -Wtautological-compare -Wformat-nonliteral -Wundef -Werror ${{env.CXXFLAGS}}
         run: |
           cmake -S . -B build_${{matrix.abi}} \
                 -DANDROID_ABI=${{matrix.abi}} \
diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index fe0b07a96..c9ac1a4c1 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -67,7 +67,7 @@ jobs:
 
       - name: Configure
         env:
-          CXXFLAGS: -Wall -Wextra -Wsign-conversion -Wtautological-compare -Werror ${{env.CXXFLAGS}}
+          CXXFLAGS: -Wall -Wextra -Wsign-conversion -Wtautological-compare -Wformat-nonliteral -Wundef -Werror ${{env.CXXFLAGS}}
         run: |
           cmake -S . -B build_${{matrix.build_type}} \
             -DBUILD_SHARED_LIBS=${{matrix.lib == 'shared'}} \
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index be09b97ba..0b20ed270 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -34,7 +34,7 @@ jobs:
       - name: Configure
         shell: bash
         env:
-          CXXFLAGS: -Wall -Wextra -Wsign-conversion -Wtautological-compare -Werror ${{env.CXXFLAGS}}
+          CXXFLAGS: -Wall -Wextra -Wsign-conversion -Wtautological-compare -Wformat-nonliteral -Wundef -Werror ${{env.CXXFLAGS}}
         run: |
           cmake -S . -B build_${{matrix.build_type}} \
                 -DCMAKE_CXX_EXTENSIONS=OFF \
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 2e6ae8cd6..72a26fa68 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -104,7 +104,7 @@ jobs:
 
       - name: Configure
         env:
-          CXXFLAGS: -Wall -Wextra -Wpedantic -Wsign-conversion -Wtautological-compare -Werror ${{env.CXXFLAGS}}
+          CXXFLAGS: -Wall -Wextra -Wpedantic -Wsign-conversion -Wtautological-compare -Wformat-nonliteral -Wundef -Werror ${{env.CXXFLAGS}}
         run: |
           if [[ ${{matrix.build_type}} == "Debug" ]]; then
             export CXXFLAGS="--coverage ${CXXFLAGS}"
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8cb747724..f166f7b96 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -145,7 +145,11 @@ check_cxx_compiler_flag (-Wunnamed-type-template-args
     HAVE_NO_UNNAMED_TYPE_TEMPLATE_ARGS)
 
 cmake_push_check_state (RESET)
-set (CMAKE_REQUIRED_LIBRARIES Threads::Threads)
+
+if (Threads_FOUND)
+  set (CMAKE_REQUIRED_LIBRARIES Threads::Threads)
+endif (Threads_FOUND)
+
 check_cxx_symbol_exists (pthread_threadid_np "pthread.h" HAVE_PTHREAD_THREADID_NP)
 cmake_pop_check_state ()
 
diff --git a/src/logging_custom_prefix_unittest.cc b/src/logging_custom_prefix_unittest.cc
index ac25f04b0..04a71787a 100644
--- a/src/logging_custom_prefix_unittest.cc
+++ b/src/logging_custom_prefix_unittest.cc
@@ -371,7 +371,7 @@ void TestRawLogging() {
   RAW_LOG(ERROR, "%s%d%c%010d%s%1x", foo->c_str(), j, ' ', j, " ", j);
   RAW_VLOG(0, "foo %d", j);
 
-#ifdef NDEBUG
+#if defined(NDEBUG)
   RAW_LOG(INFO, "foo %d", j);  // so that have same stderr to compare
 #else
   RAW_DLOG(INFO, "foo %d", j);  // test RAW_DLOG in debug mode
@@ -393,7 +393,7 @@ void TestRawLogging() {
   RAW_VLOG(2, "vlog 2 on");
   RAW_VLOG(3, "vlog 3 off");
 
-#ifdef NDEBUG
+#if defined(NDEBUG)
   RAW_DCHECK(1 == 2, " RAW_DCHECK's shouldn't be compiled in normal mode");
 #endif
 
@@ -599,7 +599,7 @@ void TestCHECK() {
 }
 
 void TestDCHECK() {
-#ifdef NDEBUG
+#if defined(NDEBUG)
   DCHECK( 1 == 2 ) << " DCHECK's shouldn't be compiled in normal mode";
 #endif
   DCHECK( 1 == 1 );
@@ -1228,7 +1228,7 @@ static void MyCheck(bool a, bool b) {
 TEST(DVLog, Basic) {
   ScopedMockLog log;
 
-#if NDEBUG
+#if defined(NDEBUG)
   // We are expecting that nothing is logged.
   EXPECT_CALL(log, Log(_, _, _)).Times(0);
 #else
@@ -1279,7 +1279,7 @@ TEST(TestExitOnDFatal, ToBeOrNotToBe) {
     // LOG(DFATAL) has severity FATAL if debugging, but is
     // downgraded to ERROR if not debugging.
     const LogSeverity severity =
-#ifdef NDEBUG
+#if defined(NDEBUG)
         GLOG_ERROR;
 #else
         GLOG_FATAL;
diff --git a/src/logging_unittest.cc b/src/logging_unittest.cc
index 72b892f62..30bad773f 100644
--- a/src/logging_unittest.cc
+++ b/src/logging_unittest.cc
@@ -348,7 +348,7 @@ void TestRawLogging() {
   RAW_LOG(ERROR, "%s%d%c%010d%s%1x", foo->c_str(), j, ' ', j, " ", j);
   RAW_VLOG(0, "foo %d", j);
 
-#ifdef NDEBUG
+#if defined(NDEBUG)
   RAW_LOG(INFO, "foo %d", j);  // so that have same stderr to compare
 #else
   RAW_DLOG(INFO, "foo %d", j);  // test RAW_DLOG in debug mode
@@ -370,7 +370,7 @@ void TestRawLogging() {
   RAW_VLOG(2, "vlog 2 on");
   RAW_VLOG(3, "vlog 3 off");
 
-#ifdef NDEBUG
+#if defined(NDEBUG)
   RAW_DCHECK(1 == 2, " RAW_DCHECK's shouldn't be compiled in normal mode");
 #endif
 
@@ -594,7 +594,7 @@ void TestCHECK() {
 }
 
 void TestDCHECK() {
-#ifdef NDEBUG
+#if defined(NDEBUG)
   DCHECK( 1 == 2 ) << " DCHECK's shouldn't be compiled in normal mode";
 #endif
   DCHECK( 1 == 1 );
@@ -1316,7 +1316,7 @@ static void MyCheck(bool a, bool b) {
 TEST(DVLog, Basic) {
   ScopedMockLog log;
 
-#if NDEBUG
+#if defined(NDEBUG)
   // We are expecting that nothing is logged.
   EXPECT_CALL(log, Log(_, _, _)).Times(0);
 #else
@@ -1367,7 +1367,7 @@ TEST(TestExitOnDFatal, ToBeOrNotToBe) {
     // LOG(DFATAL) has severity FATAL if debugging, but is
     // downgraded to ERROR if not debugging.
     const LogSeverity severity =
-#ifdef NDEBUG
+#if defined(NDEBUG)
         GLOG_ERROR;
 #else
         GLOG_FATAL;
diff --git a/src/raw_logging.cc b/src/raw_logging.cc
index 8cedabd0f..7b0f89ce3 100644
--- a/src/raw_logging.cc
+++ b/src/raw_logging.cc
@@ -68,6 +68,16 @@
 
 _START_GOOGLE_NAMESPACE_
 
+#if defined(__GNUC__)
+#define GLOG_ATTRIBUTE_FORMAT(archetype, stringIndex, firstToCheck) \
+  __attribute__((format(archetype, stringIndex, firstToCheck)))
+#define GLOG_ATTRIBUTE_FORMAT_ARG(stringIndex) \
+  __attribute__((format_arg(stringIndex)))
+#else
+#define GLOG_ATTRIBUTE_FORMAT(archetype, stringIndex, firstToCheck)
+#define GLOG_ATTRIBUTE_FORMAT_ARG(stringIndex)
+#endif
+
 // CAVEAT: vsnprintf called from *DoRawLog below has some (exotic) code paths
 // that invoke malloc() and getenv() that might acquire some locks.
 // If this becomes a problem we should reimplement a subset of vsnprintf
@@ -76,6 +86,7 @@ _START_GOOGLE_NAMESPACE_
 // Helper for RawLog__ below.
 // *DoRawLog writes to *buf of *size and move them past the written portion.
 // It returns true iff there was no overflow or error.
+GLOG_ATTRIBUTE_FORMAT(printf, 3, 4)
 static bool DoRawLog(char** buf, size_t* size, const char* format, ...) {
   va_list ap;
   va_start(ap, format);
@@ -90,7 +101,14 @@ static bool DoRawLog(char** buf, size_t* size, const char* format, ...) {
 // Helper for RawLog__ below.
 inline static bool VADoRawLog(char** buf, size_t* size,
                               const char* format, va_list ap) {
+#if defined(__GNUC__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-nonliteral"
+#endif
   int n = vsnprintf(*buf, *size, format, ap);
+#if defined(__GNUC__)
+#pragma GCC diagnostic pop
+#endif
   if (n < 0 || static_cast<size_t>(n) > *size) return false;
   *size -= static_cast<size_t>(n);
   *buf += n;
@@ -102,6 +120,7 @@ static bool crashed = false;
 static CrashReason crash_reason;
 static char crash_buf[kLogBufSize + 1] = { 0 };  // Will end in '\0'
 
+GLOG_ATTRIBUTE_FORMAT(printf, 4, 5)
 void RawLog__(LogSeverity severity, const char* file, int line,
               const char* format, ...) {
   if (!(FLAGS_logtostderr || severity >= FLAGS_stderrthreshold ||
diff --git a/src/symbolize_unittest.cc b/src/symbolize_unittest.cc
index a07ab7935..a50e44aff 100644
--- a/src/symbolize_unittest.cc
+++ b/src/symbolize_unittest.cc
@@ -71,7 +71,7 @@ static const char *TrySymbolize(void *pc) {
 #if defined(__GNUC__) && !defined(__OPENCC__)
 #  if __GNUC__ >= 4
 #    define TEST_WITH_MODERN_GCC
-#    if __i386__  // always_inline isn't supported for x86_64 with GCC 4.1.0.
+#    if defined(__i386__) && __i386__  // always_inline isn't supported for x86_64 with GCC 4.1.0.
 #      undef always_inline
 #      define always_inline __attribute__((always_inline))
 #      define HAVE_ALWAYS_INLINE