[CMake] overruling compiler fails to work

[J.S. van Bethlehem]

Hello everybody,

Let me say from the get-going: this is the worst question I could ask on 
this list because I'm pretty sure I don't provide enough information for 
a solution and the problem is likely not with CMake, but I can't think 
of anything else currently, so I'll give it a go anyway, hoping that 
someone recognizes the symptoms.

In my lists-files I write currently at the very top:
if (NOT CMAKE_CXX_COMPILER)
  set(CMAKE_CXX_COMPILER g++-4.6)
endif(NOT CMAKE_CXX_COMPILER)

It seems a bit contrived, but I use a lot of c++0x-stuff, the compiler 
on the system is still at version 4.4 and so I have to rely on a local 
installation of the more recent compiler. The if()-construct is there to 
allow setting the variable through the environment or on the cmdline. 
This worked fine for me, until this morning. I seemed to have changed 
something that causes CMake to miss this. But AFAICS I didn't change 
anything to the CMake-installation or to the lists-file(s) or to any 
part of my system for that matter. Well.... obviously I'm overlooking 
something. I put a message() before this construct and the output of 
that command appears right after all the standard messages regarding 
compilers (but used to appear before it - I know that for sure, because 
when I started to learn CMake I put a similar message there to test the 
construct I created):
-- The C compiler identification is GNU
-- The CXX compiler identification is GNU
-- Check for working C compiler: /usr/bin/gcc
-- Check for working C compiler: /usr/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Compiler = /usr/bin/c++   #   <- result of message(STATUS "Compiler = 
${CMAKE_CXX_COMPILER}") in front of the if()-construct
...

Again: I'm well aware that I don't nearly provide enough info about 
this. And odds are almost certain that no one can 'guess' what I'm 
overlooking here. My hope is just that by chance someone came across a 
similar situation and did manage to figure out what is going on. 
Hopefully that was the same mistake I'm making....

Yours sincerely,
Jakob van Bethlehem