[CMake] Visual Studio Warning Level

[James Bigler]

I manage all the warning levels by hand.

If you are truly in a rush this is what I do:

# The idea is to match a string that ends with cl but doesn't have icl in it.
set(COMPILER_NAME_REGEXPR "([^i]|^)cl.*$")
if(CMAKE_C_COMPILER MATCHES ${COMPILER_NAME_REGEXPR}
    AND CMAKE_CXX_COMPILER MATCHES ${COMPILER_NAME_REGEXPR})
  set(USING_WINDOWS_CL TRUE)
  # We should set this macro as well to get our nice trig functions
  add_definitions(-D_USE_MATH_DEFINES)
  # Microsoft does some stupid things like #define min and max.
  add_definitions(-DNOMINMAX)
endif()

# This code is kind of off the seat of my pants, but I do something similar.
if(USING_WINDOWS_CL)
  set(flag "/W4")
  # Only add the flag in once
  if(NOT CMAKE_CXX_FLAGS MATCHES "${flag}")
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${flag}" CACHE LIST
"Compile flags" FORCE)
  endif()
endif()

James