[cmake-developers] [CMake 0014721]: Ninja: warning message related to WriteUnknownExplicitDependencies() for CMakeCache.txt: file entry simply not supported yet??

[Mantis Bug Tracker]

The following issue has been SUBMITTED. 
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http://public.kitware.com/Bug/view.php?id=14721 
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Reported By:                Andreas Mohr
Assigned To:                
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Project:                    CMake
Issue ID:                   14721
Category:                   CMake
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     new
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Date Submitted:             2014-01-27 11:00 EST
Last Modified:              2014-01-27 11:00 EST
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Summary:                    Ninja: warning message related to
WriteUnknownExplicitDependencies() for CMakeCache.txt: file entry simply not
supported yet??
Description: 
See minimal test case below.

amoh at lxamoh9010:~/cmake_tests/ninja_cmakecache_txt/build$ ninja
ninja: warning: multiple rules generate CMakeCache.txt. builds involving this
target will not be correct; continuing anyway
ninja: no work to do.


Ninja 1.4.0, using CMake trunk.

Steps to Reproduce: 
cmake_minimum_required(VERSION 2.8)

project(ninja_cmakecache_txt C)

# ...and add a default target to create a backup of CMakeCache.txt,
# since that file might get destroyed too easily (at least CMake 2.6.4
# will kill it on out-of-disk-space, resulting in complete abort of
# configuration run):
if(NOT TARGET master_backup_CMakeCache)
  # CMAKE_CACHEFILE_DIR defined when cache already existing only...
  if(DEFINED CMAKE_CACHEFILE_DIR)
    # Better reference specific CMAKE_CACHEFILE_DIR variable (same as
CMAKE_BINARY_DIR).
    # Unfortunately there's no CMake file name variable for "CMakeCache.txt"
    # (source code of CMake always open-codes that name),
    # thus there's nothing to reference here.
    set(CMakeCache_file "${CMAKE_CACHEFILE_DIR}/CMakeCache.txt")
    set(CMakeCache_file_backup "${CMakeCache_file}.backup")
    add_custom_command(OUTPUT "${CMakeCache_file_backup}"
      # copy_if_different _not_ needed (target dependency needs remaking? -->
_do_ copy!)
      COMMAND "${CMAKE_COMMAND}" -E copy "${CMakeCache_file}"
"${CMakeCache_file_backup}"
      DEPENDS "${CMakeCache_file}"
      COMMENT "creating CMakeCache backup (${CMakeCache_file_backup})"
    )
    add_custom_target(master_backup_CMakeCache ALL DEPENDS
"${CMakeCache_file_backup}")
  endif(DEFINED CMAKE_CACHEFILE_DIR)
endif(NOT TARGET master_backup_CMakeCache)

file(WRITE test1.c "int main() { return 1; }")
add_library(test1 SHARED test1.c)


Additional Information: 
WriteUnknownExplicitDependencies() seems to be the function responsible for
creating/filtering out these parts.

Manually removing the part

# =============================================================================
# Unknown Build Time Dependencies.
# Tell Ninja that they may appear as side effects of build rules
# otherwise ordered by order-only dependencies.

build CMakeCache.txt: phony CMakeCache.txt


from build.ninja makes the warning message go away, in fact.


So tell me that WriteUnknownExplicitDependencies() handling simply failed to
have CMakeCache.txt listed as a build-environment-related file?
Or perhaps my sample is completely invalid since there might be a problem?
(read: "I don't know what I'm doing here" :)

Thanks,

Andreas Mohr
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Issue History 
Date Modified    Username       Field                    Change               
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2014-01-27 11:00 Andreas Mohr   New Issue                                    
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