[cmake-developers] [CMake 0015968]: Ninja generator is non-deterministic

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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https://public.kitware.com/Bug/view.php?id=15968 
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Reported By:                Chris
Assigned To:                
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Project:                    CMake
Issue ID:                   15968
Category:                   CMake
Reproducibility:            always
Severity:                   major
Priority:                   high
Status:                     new
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Date Submitted:             2016-02-10 12:13 EST
Last Modified:              2016-02-10 12:13 EST
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Summary:                    Ninja generator is non-deterministic
Description: 
CMake's Ninja generator is non-deterministic on our project (LLVM). This is
trivially reproducible by configuring llvm into a clean directory multiple times
and comparing the results.

This is a very real problem for our project because the nondeterminism in the
generated ninja build seems to be the cause of non-determinism in our build
outputs. One of the important methods of compiler testing is what we call a
3-stage build. The process is basically:

(1) build clang
(2) use clang from step 1 to build clang again
(3) use clang from step 2 to build clang again
(4) ensure clang from step 2 and clang from step 3 are binary identical

Today this works using the CMake Unix Makefile generator, but not using the
Ninja generator. This issue reproduces on CMake 3.4.x and CMake 3.5.0 rc1. I
assume it probably goes back quite a long ways too.

Steps to Reproduce: 
mkdir scratch
cd scratch
cmake -G Ninja <path to llvm>
cp build.ninja ..
rm -rf
cmake -G Ninja <path to llvm>
diff build.ninja ../build.ninja
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Issue History 
Date Modified    Username       Field                    Change               
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2016-02-10 12:13 Chris          New Issue                                    
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