[cmake-developers] [CMake 0015757]: Including a project from parent subdirectory causes CMake to produce wrong build files for Ninja generator

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://public.kitware.com/Bug/view.php?id=15757 
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Reported By:                Pavel Solodovnikov
Assigned To:                
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Project:                    CMake
Issue ID:                   15757
Category:                   CMake
Reproducibility:            always
Severity:                   major
Priority:                   high
Status:                     new
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Date Submitted:             2015-09-23 05:28 EDT
Last Modified:              2015-09-23 05:28 EDT
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Summary:                    Including a project from parent subdirectory causes
CMake to produce wrong build files for Ninja generator
Description: 
Suppose we have following project structure:

testing_ninja/
--- mylib1/
------ CMakeLists.txt
------ src.cpp
--- mylib2/
------ CMakeLists.txt
------ src.cpp

CMakeLists.txt for mylib1 creates a library mylib1.dll, which exports some
symbols needed by mylib2, so mylib2 depends on mylib1 ( via
target_link_libraries(mylib2 mylib1) ). If mylib1 CMakelists.txt contains
following line, which includes mylib2 project:

add_subdirectory("../mylib2" "../mylib2")

then if we use Ninja generator to produce build files (invoking cmake inside
mylib1 directory), the generated build.ninja file contains errors.

CMake-generated build.ninja file contains mixed absolute-relative paths for
mylib1.lib target which confuses ninja in such a way:

when ninja is invoked it immediately reports an error that it couldn't find
mylib1.lib binary needed by mylib2 (however it should be generated at build time
and ninja should not rely on its existence). Error message is as follows:

E:\testing_ninja\mylib1>ninja
ninja: error: 'E:/testing_ninja/mylib1/mylib1.lib', needed by 'E:/testing_ninja/
mylib2/mylib2.dll', missing and no known rule to make it

As I understand it happens because CMake generates a list of phony targets for
each build target (expressed via relative path to target), so ninja does not
need these files to exist at the beginning of build. And because CMake is mixing
up relative and absolute paths in this case, ninja does not recognize phony
targets anymore (they are expressed as absolute paths now) and fails. If I move
mylib2 project inside mylib1 directory so the whole source tree stays inside the
folder in which the root CMakeLists.txt file is placed, this behavior does not
happen.

To note one important moment: this only does happen if mylib1 appears to be
dynamic library, if we build static libraries instead everything is alright.

I've attached a test project to demonstrate such behavior. Tested only on
Windows but I assume that it could be reproduced under the same conditions on
other platforms.

Steps to Reproduce: 
1) Extract attached archive
2) Invoke cmake inside mylib1 directory with following arguments:
cmake -G "Ninja" .
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Issue History 
Date Modified    Username       Field                    Change               
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2015-09-23 05:28 Pavel SolodovnikovNew Issue                                    
2015-09-23 05:28 Pavel SolodovnikovFile Added: testing_ninja.zip                
   
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