Add a CMake option to not turn warnings into errors

We have some warnings in Release configuration because of:
- unused arguments (some calls to `assert`, that are completly removed in
  release mode, cause some arguments to be unused) in such a pattern:

    void f(bool b)
    {
        assert(b);
    }
- strict aliasing rules violation in floating point tests. Since this is only
  test code, it is not considered critical.

Add an option (on by default) to add the -Werror flag. Have travis travis build
the Parameter Framework in "Release" configuration (it previously built in
"Debug" and "None" configurations) without the -Werror flag. Also, forcefully
remove the "/WX" flag on windows (equivalent to -Werror) because we are not
warning-free yet, even in debug mode.

Signed-off-by: David Wagner <[email protected]>

Author: dawagner

.travis.yml

@@ -57,13 +57,13 @@ script:
         make -j &&
         CTEST_OUTPUT_ON_FAILURE=1 make ExperimentalTest ExperimentalMemCheck )
   - ( mkdir build && cd build &&
-        cmake -DCMAKE_PREFIX_PATH=$PREFIX -DCMAKE_INSTALL_PREFIX=../install .. &&
+        cmake -DCMAKE_PREFIX_PATH=$PREFIX -DCMAKE_INSTALL_PREFIX=../install -DCMAKE_BUILD_TYPE=Release .. &&
         make -j &&
         CTEST_OUTPUT_ON_FAILURE=1 make test &&
         make install &&
         cpack --verbose -G DEB && dpkg --info *.deb)
   - ( cd skeleton-subsystem &&
-        cmake -DCMAKE_INSTALL_PREFIX=../install . &&
+        cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=../install . &&
         make &&
         CTEST_OUTPUT_ON_FAILURE=1 make ExperimentalTest ExperimentalMemCheck &&
         make install )

CMakeLists.txt

@@ -42,7 +42,7 @@ option(DOXYGEN "Enable doxygen generation (you still have to run 'make doc')" OF
 option(REQUIREMENTS "Generate the html version of the 'requirements' documentation" OFF)
 option(PYTHON_BINDINGS "Python library to use the Parameter Framework from python" ON)
 option(C_BINDINGS "Library to use the Parameter Framework using a C API" ON)
-
+option(FATAL_WARNINGS "Turn warnings into errors (-Werror flag)" ON)
 
 # find and set the Parameter Framework's version
 execute_process(COMMAND git describe --tags --dirty
@@ -73,8 +73,14 @@ if(WIN32)
     # only public methods instead of the whole class, but they are too many to
     # do that. A separated plugin interface would fix that.
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4 /FIiso646.h -wd4127 -wd4251")
+
+    # FIXME: Once we have removed all warnings on windows, add the /WX flags if
+    # FATAL_WARNINGS is enabled
 else()
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Werror -Wall -Wextra -Wconversion -Wno-sign-conversion")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wextra -Wconversion -Wno-sign-conversion")
+    if(FATAL_WARNINGS)
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror")
+    endif()
 endif()
 
 # Hide symbols by default, then exposed symbols are the same in linux and windows

bindings/python/CMakeLists.txt

@@ -50,7 +50,10 @@ find_package(PythonLibs ${PYTHON_VERSION_STRING} EXACT REQUIRED)
 include_directories(${PYTHON_INCLUDE_DIRS})
 
 set_property(SOURCE pfw.i PROPERTY CPLUSPLUS ON)
-set_property(SOURCE pfw.i PROPERTY SWIG_FLAGS "-Wall" "-Werror")
+set_property(SOURCE pfw.i PROPERTY SWIG_FLAGS "-Wall")
+if(FATAL_WARNINGS)
+    set_property(SOURCE pfw.i APPEND PROPERTY SWIG_FLAGS "-Werror")
+endif()
 
 swig_add_module(PyPfw python pfw.i)
 swig_link_libraries(PyPfw parameter ${PYTHON_LIBRARIES})
@@ -70,7 +73,8 @@ set_property(TARGET _PyPfw PROPERTY LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BIN
 # spurious anyway, as it relates to "ILogger *" which is an abstract
 # class/interface class and as such cannot be destroyed.
 # -Wno-error is set to prevent compilation failure in case of the code
-# generated by swig generates warnings
+# generated by swig generates warnings. We don't apply the FATAL_WARNING policy
+# here, since we consider this generated code as external.
 target_compile_definitions(_PyPfw PRIVATE SWIG_PYTHON_SILENT_MEMLEAK)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-error")