[CMake] ccmake gets all squirrelly over which C++ compiler to use.

[Mathieu Malaterre]

I have had this issue an infinite number of time. Debian packager
would be using inconsistant c++ compiler and I could not use both ITK
and VTK at the same time (from debian package). So I provided an
(undocumented) hack:
CMAKE_OVERRIDE_COMPILER_MISMATCH

2cts

On Mon, Mar 2, 2009 at 8:27 PM, kent williams <nkwmailinglists at gmail.com> wrote:
> Version 2.6 patch 2 on OS X and Linux -- you know your code is
> portable when the same issue happens on multiple platforms!
>
> Here's the scenario -- a guy in our department was having trouble
> getting ccmake to generate makefiles.
>
> My diagnosis was pretty simple: His project depended on both ITK and
> VTK. ITK had been compiled with and VTK had been compiled with
> '/usr/bin/g++'.  So he got into an infinite loop where CMake would
> force the CMAKE_CXX_COMPILER to '/usr/bin/c++' when it processed
> UseITK.cmake, then when it processed UseVTK.cmake, it woud force it
> back to '/usr/bin/g++'.  Then it would tell you it had to delete
> CMakeCache.txt, and re-run the Configuration pass.
>
> This turns the CCMake run into effectively an endless loop with a
> human in the loop, endlessly trying to reconfigure.
>
> The solution was obvious -- make sure both VTK and ITK use the same
> compiler Of course on most machines /usr/bin/c++ is a symbolic link to
> /usr/bin/g++ (or vice versa) but CCMake can't assume that's the
> case...
>
> But here is the real problem, the 'squirrelyness' referred to in the
> subject line:
>
> In ccmake, once VTK and ITK were built with the same compiler, I
> changed CMAKE_CXX_COMPILER to match what VTK and ITK were reporting,
> set ITK_DIR and VTK_DIR , and hit compile.
>
> But again it would pop up a warning, and when I exited the warning
> screen, CCMake had forgotten what I'd entered for CMAKE_CXX_COMPILER,
> ITK_DIR, and VTK_DIR, so I had to type them in a second time.  Once I
> did that, the Configure pass would finish and I could get through the
> Generate pass.
>
> This is one specific case, but I've noticed in general that if the
> Configure pass has an error, it forgets everything you just entered
> and you have to re-enter it, and fix the error, and Configure again.
> This is extremely frustrating, like dying in a video game and having
> to go back and re-run all levels to get back to where you died.
>
> What's the story? Can this be fixed?
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-- 
Mathieu