[cmake] Require and enforce C++11 project wide.

  - Instead of allowing C++11 on a target by target basis when needed,
    enable it globally. We would not be able to have a working omc or
    simulation as it is now without a compiler with C++11 support. So
    require it globally.

  - Unfortunately, we can not enforce c89/90 standards on our code at the
    moment as we rely heavily on C99 features and GNU extensions.

OMCompiler/CMakeLists.txt

@@ -18,7 +18,6 @@ string(REPLACE "-DNDEBUG" "" CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}
 string(REPLACE "-DNDEBUG" "" CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO}")
 string(REPLACE "-DNDEBUG" "" CMAKE_C_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")
 
-# set(CMAKE_VERBOSE_MAKEFILE ON)
 
 # include utility macros.
 include(.cmake/omc_utils.cmake)
@@ -30,6 +29,20 @@ omc_add_to_report(CMAKE_CXX_COMPILER_ID)
 omc_add_to_report(CMAKE_C_COMPILER_ID)
 omc_add_to_report(CMAKE_LIBRARY_ARCHITECTURE)
 
+#########################################################################################################
+## Set the C standard to use. Unfortunately, we can not enforce c90.
+## Our sources contain a lot of c99 and gnu extension code.
+# set(CMAKE_C_STANDARD 90)
+
+## Set the C++ standard to use.
+set(CMAKE_CXX_STANDARD 11)
+set(CXX_STANDARD_REQUIRED ON)
+## Make sure we do not start relying on extensions down the road.
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+#########################################################################################################
+## Enable verbose Makefiles if you want to debug. (you can also instead use 'make VERBOSE=1')
+# set(CMAKE_VERBOSE_MAKEFILE ON)
 
 # Export compile commands (compile_commands.json) for each source file. This helps editors (e.g. vscode, emacs) have
 # a more accurate code navigation and intellisense. E.g. includes can be pinpointed instead of

OMCompiler/Compiler/CMakeLists.txt

@@ -150,7 +150,6 @@ add_custom_target(INTERFACE_CHECK
 # Add a small dependency scanner program. This reads a list of list of dependencies and generates
 # a list of dependents for each entry.
 add_executable(dep_scanner ${CMAKE_CURRENT_SOURCE_DIR}/.cmake/dep_scanner.cpp)
-target_compile_features(dep_scanner PRIVATE cxx_std_11)
 
 # Write out a new line separated list of all MM source files to a list so that it can be easily
 # parsed by the small MetaModelica dependency scanner we have now. (c++ code)

OMCompiler/Compiler/runtime/CMakeLists.txt

@@ -69,7 +69,6 @@ add_library(omcruntime STATIC)
 add_library(omc::compiler::runtime ALIAS omcruntime)
 
 target_sources(omcruntime PRIVATE ${OMC_RUNTIIME_SOURCES})
-target_compile_features(omcruntime PRIVATE cxx_std_11)
 
 target_link_libraries(omcruntime PUBLIC omc::config)
 target_link_libraries(omcruntime PUBLIC CURL::libcurl)