[CMake] Variable scope

[Jorge Rodriguez]

I'm experiencing some strange behavior with variable scope in cmake 2.0.5.

To explain the situation, say I have this directory structure:

CMakeLists.txt
include.cmake
src/CMakeLists.txt

include.cmake has this:

# Figure out what version of the C++ compiler we're using so we
# can tag dlls with it later.
SET(VS_COMPILER "60")

IF(WIN32)
  EXEC_PROGRAM(cl OUTPUT_VARIABLE COMPILER_VERSION)
  IF(COMPILER_VERSION MATCHES ".*13\\.10.*")
    SET(VS_COMPILER "71")
  ENDIF(COMPILER_VERSION MATCHES ".*13\\.10.*")
ENDIF(WIN32)

in CMakeLists.txt (top-level) you have this:

PROJET(PROJ)
SET(VS_COMPILER "60")
INCLUDE(${PROJ_SOURCE_DIR}/include.cmake)
MESSAGE("Compiler 1: ${VS_COMPILER}")
SUBDIRS(src)

and in srcs/CMakeLists.txt:

MESSAGE("Compiler 2: ${VS_COMPILER}")

The output of this when cmake is run is:

Compiler 1: 71
Compiler 2: 60

So, it seems that the value of VS_COMPILER set in include.cmake is reset 
in the srcs subdirectory to what it was originally set to. Am I 
hallucinating?

Also, it's fairly apparent that the goal of this arrangement is to 
determine what version of Microsoft's Visual Studio compiler is being 
used. Is there a better way of doing that which I should be using instead?