[cmake-developers] [CMake 0013889]: Multiple add_custom_command for the same output file lead to multiple rules being generated for the same file

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://www.cmake.org/Bug/view.php?id=13889 
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Reported By:                Micha Hergarden
Assigned To:                
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Project:                    CMake
Issue ID:                   13889
Category:                   CMake
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
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Date Submitted:             2013-02-04 06:00 EST
Last Modified:              2013-02-04 06:00 EST
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Summary:                    Multiple add_custom_command for the same output file
lead to multiple rules being generated for the same file
Description: 
The cmake ninja generator adds multiple build rules for the same file, when
there are multiple add_custom_command supplied in subdirectories. When ninja is
run with the generated build.ninja file this leads to the following warning:

ninja: warning: multiple rules generate /tmp/test.c. build will not be correct;
continuing anyway

I am using the latest ninja from the git repository:
https://github.com/martine/ninja.git
commit 05736568b9a26599865dd7452e62f70ecdbc9e41

Steps to Reproduce: 
1. Create a CMakeLists.txt file which adds two subdirectories, e.g.:

cmake_minimum_required(VERSION 2.8)
ADD_SUBDIRECTORY(tst1)
ADD_SUBDIRECTORY(tst2)

2. Create two CMakeLists.txt files for the subdirectories, both of which add a
custom command for the same output file, and an executable using that file,
e.g.:
ADD_CUSTOM_COMMAND(OUTPUT /tmp/test.c COMMAND cmake ARGS -E copy
/home/test/test.c /tmp/test.c)
ADD_EXECUTABLE(test1 /tmp/test.c)

3. Run cmake -G Ninja
   You can now examine the build.ninja file to see the multiple build rules
4. Run ninja
   You will now see the ninja warning.

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Issue History 
Date Modified    Username       Field                    Change               
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2013-02-04 06:00 Micha HergardenNew Issue                                    
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