How to set warning level in CMake?

Question

How to set the warning level for a project (not the whole solution) using CMake? Should work on Visual Studio and GCC.

I found various options but most seem either not to work or are not consistent with the documentation.

Answer 1

Here is the best solution I found so far (including a compiler check):

if(CMAKE_BUILD_TOOL MATCHES "(msdev|devenv|nmake)")
    add_definitions(/W2)
endif()

This will set warning level 2 in Visual Studio. I suppose with a -W2 it would work in GCC too (untested).

Answer 2

You can do something similar to this:

if(MSVC)
  # Force to always compile with W4
  if(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
    string(REGEX REPLACE "/W[0-4]" "/W4" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
  else()
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4")
  endif()
elseif(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
  # Update if necessary
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wno-long-long -pedantic")
endif()