Ignore warnings in external modules when using CMake

Question

I am using CMake GUI (no version) with CMake 3.6.1. I am using an external module with add_subdirectory that shows me some warnings th

Answer 1

Turning my comments into an answer

That sounds like your external module does have a project() command. This resets the policies for this sub-module and below.

To demonstrate a possible solution, lets say you have a external project as the following:

g3log/CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
project(g3log NONE)

set(VAR1 "Hello World")
set(VAR2 "VAR1")
if ("${VAR2}" STREQUAL "${VAR1}")
    message("CMP0054 old behavior")
endif()

You can now set CMAKE_POLICY_DEFAULT_CMP0054 to OLD (or even better to NEW; nobody really wanted the "OLD" behavior) to get rid of the "Policy CMP0054 is not set" warnings you will get with newer versions of CMake:

CMakeLists.txt

cmake_minimum_required(VERSION 3.1)
project(PolicyOverwrite NONE)

set(CMAKE_POLICY_DEFAULT_CMP0054 NEW)
add_subdirectory(g3log)

Now you have set a default for policy CMP0054 to be used if none is explicitly given in your project or one of the external projects you are using.