Treat warnings as errors in CI builds

The CMake files now add "-Werror"/"/WX" if the "WERROR" CMake variable
is true.  By default it is not; the CI builds set this.

Signed-off-by: Erik Boasson <eb@ilities.com>

.travis.yml

@@ -164,6 +164,7 @@ script:
           -DCMAKE_INSTALL_PREFIX=$(pwd)/install
           -DUSE_SANITIZER=${ASAN}
           -DBUILD_TESTING=on
+          -DWERROR=on
           -G "${GENERATOR}" ../src
   - ${SCAN_BUILD} cmake --build . --config ${BUILD_TYPE} --target install
   - CYCLONEDDS_URI='<CycloneDDS><DDSI2E><Internal><EnableExpensiveChecks>all</EnableExpensiveChecks></Internal></DDSI2E></CycloneDDS>' ctest -T test -C ${BUILD_TYPE}

appveyor.yml

@@ -36,7 +36,7 @@ build_script:
   - mkdir build
   - cd build
   - conan install -s arch=%ARCH% -s build_type=%CONFIGURATION% ..
-  - cmake -DBUILD_TESTING=on -DCMAKE_BUILD_TYPE=%CONFIGURATION% -DCMAKE_INSTALL_PREFIX=%CD%/install -G "%GENERATOR%" ../src
+  - cmake -DBUILD_TESTING=on -DWERROR=ON -DCMAKE_BUILD_TYPE=%CONFIGURATION% -DCMAKE_INSTALL_PREFIX=%CD%/install -G "%GENERATOR%" ../src
   - cmake --build . --config %CONFIGURATION% --target install -- /maxcpucount
   - cd install/share/CycloneDDS/examples/helloworld
   - mkdir build

src/CMakeLists.txt

@@ -22,6 +22,11 @@ if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
     "Debug" "Release" "MinSizeRel" "RelWithDebInfo")
 endif()
 
+# By default don't treat warnings as errors, else anyone building it with a different compiler that
+# just happens to generate a warning, as well as anyone adding or modifying something and making a
+# small mistake would run into errors.  CI builds can be configured differently.
+option(WERROR "Treat compiler warnings as errors" OFF)
+
 FUNCTION(PREPEND var prefix)
    SET(listVar "")
    FOREACH(f ${ARGN})
@@ -86,18 +91,30 @@ endif()
 
 # Set reasonably strict warning options for clang, gcc, msvc
 # Enable coloured ouput if Ninja is used for building
-if(${CMAKE_C_COMPILER_ID} STREQUAL "Clang" OR ${CMAKE_C_COMPILER_ID} STREQUAL "AppleClang")
-  add_definitions(-Wall -Wextra -Wconversion -Wunused -Wmissing-prototypes)
-  if(${CMAKE_GENERATOR} STREQUAL "Ninja")
-    add_definitions(-Xclang -fcolor-diagnostics)
+if("${CMAKE_C_COMPILER_ID}" STREQUAL "Clang" OR "${CMAKE_C_COMPILER_ID}" STREQUAL "AppleClang")
+  #message(STATUS clang)
+  add_compile_options(-Wall -Wextra -Wconversion -Wunused -Wmissing-prototypes)
+  if(${WERROR})
+    add_compile_options(-Werror)
   endif()
-elseif(${CMAKE_C_COMPILER_ID} STREQUAL "GNU")
-  add_definitions(-Wall -Wextra -Wconversion -Wmissing-prototypes)
-  if(${CMAKE_GENERATOR} STREQUAL "Ninja")
-    add_definitions(-fdiagnostics-color=always)
+  if("${CMAKE_GENERATOR}" STREQUAL "Ninja")
+    add_compile_options(-Xclang -fcolor-diagnostics)
+  endif()
+elseif("${CMAKE_C_COMPILER_ID}" STREQUAL "GNU")
+  #message(STATUS gcc)
+  add_compile_options(-Wall -Wextra -Wconversion -Wmissing-prototypes)
+  if(${WERROR})
+    add_compile_options(-Werror)
+  endif()
+  if("${CMAKE_GENERATOR}" STREQUAL "Ninja")
+    add_compile_options(-fdiagnostics-color=always)
+  endif()
+elseif("${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC")
+  #message(STATUS msvc)
+  add_compile_options(/W3)
+  if(${WERROR})
+    add_compile_options(/WX)
   endif()
-elseif(${CMAKE_C_COMPILER_ID} STREQUAL "MSVC")
-  add_definitions(/W3)
 endif()
 
 # I don't know how to enable warnings properly so that it ends up in Xcode projects as well