[cmake-developers] [CMake 0014294]: Command-line options overwritten by re-run

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://public.kitware.com/Bug/view.php?id=14294 
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Reported By:                Greg Coombe
Assigned To:                
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Project:                    CMake
Issue ID:                   14294
Category:                   CMake
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
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Date Submitted:             2013-07-15 20:17 EDT
Last Modified:              2013-07-15 20:17 EDT
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Summary:                    Command-line options overwritten by re-run
Description: 
If I specify a command-line option using the "option()" function and provide it
on the command line along with CMAKE_<lang>_COMPILER option (specified without
full path), it is overwritten. 

Steps to Reproduce: 
1. Make a small CMakeLists.txt:

cmake_minimum_required(VERSION 2.8.11)
option(RERUN_TEST "Re-run me!" OFF)
message(STATUS "Re-run test variable is " ${RERUN_TEST})


2. Run twice with both the option specified, as well as the compiler:

$ cmake  -D RERUN_TEST=ON -D CMAKE_CXX_COMPILER=g++ CMakeLists.txt
-- The C compiler identification is GNU 4.6.3
-- The CXX compiler identification is GNU 4.6.3
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/g++
-- Check for working CXX compiler: /usr/bin/g++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Re-run test variable is ON
-- Configuring done
-- Generating done


$ cmake  -D RERUN_TEST=ON -D CMAKE_CXX_COMPILER=g++ CMakeLists.txt
-- Re-run test variable is ON
-- Configuring done
You have changed variables that require your cache to be deleted.
Configure will be re-run and you may have to reset some variables.
The following variables have changed:
CMAKE_CXX_COMPILER= g++

-- The C compiler identification is GNU 4.6.3
-- The CXX compiler identification is GNU 4.6.3
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/g++
-- Check for working CXX compiler: /usr/bin/g++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Re-run test variable is OFF
-- Configuring done
-- Generating done


So now we've built the project without the command-line option.

3. Interestingly, note that using the full path of the compiler doesn't have the
same behavior:

$ cmake  -D RERUN_TEST=ON -D CMAKE_CXX_COMPILER=/usr/bin/g++ CMakeLists.txt
-- Re-run test variable is ON
-- Configuring done
-- Generating done




Additional Information: 
Speculation:
It appears that CMake is writing the CMAKE_<lang>_COMPILER value to the cache
before expanding it, then interpreting the different value as requiring a
re-run. This re-run ignores the command-line options (maybe because the cache is
nuked: http://public.kitware.com/Bug/view.php?id=13756).
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Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2013-07-15 20:17 Greg Coombe    New Issue                                    
2013-07-15 20:17 Greg Coombe    File Added: CMakeLists.txt                    
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