diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 0e5f8982..474741f3 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -21,7 +21,7 @@ basic-build-fork:
   script:
     - sh build/gitlab-ci cmake "Unix Makefiles" Debug static
 
-basic-build-main:
+basic-build:
   stage: pre-build
   rules:
     - if: '$CI_PROJECT_PATH == "libtiff/libtiff"'
diff --git a/build/gitlab-ci b/build/gitlab-ci
index 6e6c72d1..76852880 100644
--- a/build/gitlab-ci
+++ b/build/gitlab-ci
@@ -45,7 +45,7 @@ cmake_build()
     fi
     mkdir cmake-build
     cd cmake-build
-    opts="-Dfatal-warnings=ON"
+    opts="-Dfatal-warnings=ON -Dextra-warnings=ON -Dcxx-compat-warnings=ON"
     para3=`echo "$3" | sed 's/./\L&/g'`
     if [ "$para3" = "static" ]; then
         opts2="-DBUILD_SHARED_LIBS:BOOL=OFF"
@@ -55,7 +55,7 @@ cmake_build()
         opts2=""
     fi
     echo "Running cmake -G "$1" -DCMAKE_UNITY_BUILD=ON -DCMAKE_BUILD_TYPE="$2" -DCMAKE_INSTALL_PREFIX=../cmake-install ${opts} ${opts2} .."
-    cmake -G "$1" -DCMAKE_UNITY_BUILD=ON -DCMAKE_BUILD_TYPE="$2" -DCMAKE_INSTALL_PREFIX=../cmake-install -DCMAKE_C_FLAGS="-Wall -Wextra -Werror" -Dcxx-compat-warnings=ON ${opts} ${opts2} ..
+    cmake -G "$1" -DCMAKE_UNITY_BUILD=ON -DCMAKE_BUILD_TYPE="$2" -DCMAKE_INSTALL_PREFIX=../cmake-install ${opts} ${opts2} ..
     $COVERITY_BUILD cmake --build .
     cmake --build . --target install
     ctest -V
diff --git a/build/gitlab-ci-cygwin b/build/gitlab-ci-cygwin
index a5d0342d..582c03e9 100644
--- a/build/gitlab-ci-cygwin
+++ b/build/gitlab-ci-cygwin
@@ -51,7 +51,7 @@ cmake --version
 gcc --version || { echo "gcc not found in Cygwin"; exit 1; }
 
 # Configure CMake options
-CMAKE_OPTS="-Dfatal-warnings=ON"
+CMAKE_OPTS="-Dfatal-warnings=ON -Dextra-warnings=ON -Dcxx-compat-warnings=ON"
 CMAKE_OPTS="$CMAKE_OPTS -DCMAKE_UNITY_BUILD=ON"
 CMAKE_OPTS="$CMAKE_OPTS -DCMAKE_C_FLAGS=-Wall -Wextra -Werror"
 
diff --git a/build/gitlab-ci-mingw b/build/gitlab-ci-mingw
index c3300a01..1d7858d0 100644
--- a/build/gitlab-ci-mingw
+++ b/build/gitlab-ci-mingw
@@ -53,7 +53,7 @@ cmake --version
 gcc --version || { echo "gcc not found in MinGW"; exit 1; }
 
 # Configure CMake options
-CMAKE_OPTS="-Dfatal-warnings=ON"
+CMAKE_OPTS="-Dfatal-warnings=ON -Dextra-warnings=ON -Dcxx-compat-warnings=ON"
 CMAKE_OPTS="$CMAKE_OPTS -DCMAKE_UNITY_BUILD=ON"
 CMAKE_OPTS="$CMAKE_OPTS -DCMAKE_C_FLAGS=-Wall -Wextra -Werror"
 
diff --git a/build/gitlab-ci.ps1 b/build/gitlab-ci.ps1
index 8320da23..075f979f 100644
--- a/build/gitlab-ci.ps1
+++ b/build/gitlab-ci.ps1
@@ -210,7 +210,8 @@ function Invoke-CMakeConfigure {
             "-DCMAKE_INSTALL_PREFIX=$InstallDir",
             "-DCMAKE_UNITY_BUILD=ON",
             "-Dfatal-warnings=ON",
-            "-Dextra-warnings=ON"
+            "-Dextra-warnings=ON",
+            "-Dcxx-compat-warnings=ON"
         )
 
         # Add vcpkg toolchain if available
@@ -235,9 +236,6 @@ function Invoke-CMakeConfigure {
             $cmakeArgs += "-DBUILD_SHARED_LIBS=ON"
         }
 
-        # Add MSVC-specific warning flags
-        $cmakeArgs += "-DCMAKE_C_FLAGS=/W4 /WX"
-
         $cmakeArgs += $SourceDir
 
         Write-Host "Running: cmake $($cmakeArgs -join ' ')"
diff --git a/cmake/CompilerChecks.cmake b/cmake/CompilerChecks.cmake
index 71f08127..39b62ef0 100644
--- a/cmake/CompilerChecks.cmake
+++ b/cmake/CompilerChecks.cmake
@@ -29,9 +29,17 @@ include(CheckCCompilerFlag)
 
 # These are annoyingly verbose, produce false positives or don't work
 # nicely with all supported compiler versions, so are disabled unless
-# explicitly enabled.
+# explicitly enabled.  These warnings are expected to be clean for
+# CI builds when combined with fatal-warnings.
 option(extra-warnings "Enable extra compiler warnings" OFF)
 
+# These are annoyingly verbose, produce false positives or don't work
+# nicely with all supported compiler versions, so are disabled unless
+# explicitly enabled.  Not used in CI builds because it cannot be
+# guaranteed that the builds will be warning-free and so cannot be
+# combined with fatal-warnings without breaking the builds.
+option(broken-warnings "Enable compiler warnings which will warn erroneously or are broken on some platforms" OFF)
+
 # This will cause the compiler to fail when an error occurs.
 option(fatal-warnings "Compiler warnings are errors" OFF)
 
@@ -71,6 +79,10 @@ if(CMAKE_C_COMPILER_ID STREQUAL "GNU" OR
         list(APPEND test_flags
                 -pedantic
                 -Wextra
+        )
+    endif()
+    if(broken-warnings)
+        list(APPEND test_flags
                 -Wformat
                 -Wformat-overflow
                 -Wformat-nonliteral