[cmake-developers] [CMake 0014771]: Ninja generator does not always honor SYMBOLIC rules with no command

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://www.cmake.org/Bug/view.php?id=14771 
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Reported By:                Brad King
Assigned To:                
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Project:                    CMake
Issue ID:                   14771
Category:                   CMake
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
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Date Submitted:             2014-02-25 09:50 EST
Last Modified:              2014-02-25 09:50 EST
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Summary:                    Ninja generator does not always honor SYMBOLIC rules
with no command
Description: 
The SYMBOLIC source file property is a mark typically used on a custom command
output to say that the file will never actually exist.  This can be used to
create always-out-of-date rules that run on every build.

When a custom command has no actual command line and a symbolic output the Ninja
generator implements this by creating a phony build rule.  However, the Ninja
documentation states:

 "If a phony build statement is written without any dependencies,
  the target will be considered out of date if it does not exist."

If there are order-only dependencies then Ninja does not consider a phony target
to be out of date.


Steps to Reproduce: 
$ cat ../CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
project(OrderedBuildAlways NONE)
add_custom_target(first)
add_custom_command(
  OUTPUT never-created
  COMMAND
  VERBATIM
  )
add_custom_command(
  OUTPUT always-printed
  COMMAND ${CMAKE_COMMAND} -E echo "always printed"
  COMMAND ${CMAKE_COMMAND} -E touch always-printed
  DEPENDS never-created
  VERBATIM
  )
set_property(SOURCE never-created PROPERTY SYMBOLIC 1)
add_custom_target(drive ALL DEPENDS always-printed)
add_dependencies(drive first)

$ cmake .. -G Ninja
$ ninja
[1/1] Generating always-printed
always printed
$ ninja
ninja: no work to do.

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Issue History 
Date Modified    Username       Field                    Change               
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2014-02-25 09:50 Brad King      New Issue                                    
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