CMakeLists.txt: various fixes

Bumped minimal version of cmake to 3.5, because versions below
3.5 will be removed soon from cmake. Removed manual setting
of optimization flags. These are already set to decent defaults, and
it should be possible to set them from the outside if need be.

Also made an option SOPHUS_INSANE_CFLAGS which defaults to off. The
issue is, that (more) modern compilers will not compile the tests / code
with -Werror on. Werror is therefore harmful to production, albeit
useful for developers. Hence, it is an option to be set.

Signed-off-by: Matthias Schoepfer <matthias.schoepfer@googlemail.com>

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 project(Sophus VERSION 1.22.10)
 
 include(CMakePackageConfigHelpers)
@@ -17,6 +17,8 @@ endif ()
 option(SOPHUS_INSTALL "Generate the install target." ${SOPHUS_MASTER_PROJECT})
 option(SOPHUS_USE_BASIC_LOGGING "Use basic logging (in ensure and test macros)" OFF)
 
+option(SOPHUS_INSANE_CFLAGS "Add a bunch of extra cflags to expose more warnings" OFF)
+
 if(SOPHUS_MASTER_PROJECT)
   # Release by default
   # Turn on Debug with "-DCMAKE_BUILD_TYPE=Debug"
@@ -27,17 +29,15 @@ if(SOPHUS_MASTER_PROJECT)
   set(CMAKE_CXX_STANDARD 14)
 
   # Set compiler specific settings (FixMe: Should not cmake do this for us automatically?)
-  IF("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-    SET(CMAKE_CXX_FLAGS_DEBUG  "-O0 -g")
-    SET(CMAKE_CXX_FLAGS_RELEASE "-O3")
+  IF("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND ${SOPHUS_INSANE_CFLAGS})
     SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -Wextra  -Wno-deprecated-register -Qunused-arguments -fcolor-diagnostics")
   ELSEIF("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
-    SET(CMAKE_CXX_FLAGS_DEBUG  "-O0 -g")
-    SET(CMAKE_CXX_FLAGS_RELEASE "-O3")
-    SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -Wextra -std=c++14 -Wno-deprecated-declarations -ftemplate-backtrace-limit=0")
     SET(CMAKE_CXX_FLAGS_COVERAGE "${CMAKE_CXX_FLAGS_DEBUG} --coverage -fno-inline -fno-inline-small-functions -fno-default-inline")
     SET(CMAKE_EXE_LINKER_FLAGS_COVERAGE "${CMAKE_EXE_LINKER_FLAGS_DEBUG} --coverage")
     SET(CMAKE_SHARED_LINKER_FLAGS_COVERAGE "${CMAKE_SHARED_LINKER_FLAGS_DEBUG} --coverage")
+    IF (${SOPHUS_INSANE_CFLAGS})
+      SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -Wextra -Wno-deprecated-declarations -ftemplate-backtrace-limit=0")
+    ENDIF()
   ELSEIF(CMAKE_CXX_COMPILER_ID MATCHES "^MSVC$")
     ADD_DEFINITIONS("-D _USE_MATH_DEFINES /bigobj /wd4305 /wd4244 /MP")
   ENDIF()