MantisBT - CMake
View Issue Details
IDProjectCategoryView StatusDate SubmittedLast Update
0015116CMakeCMakepublic2014-08-29 13:112015-11-02 09:13
ReporterVijay Pradeep 
Assigned ToBrad King 
PrioritynormalSeverityminorReproducibilityalways
StatusclosedResolutionfixed 
PlatformLinuxOSUbuntuOS Version12.04
Product VersionCMake 2.8.12.2 
Target VersionCMake 3.2.1Fixed in VersionCMake 3.2.1 
Summary0015116: cmake add_custom_command issue with multiple output files
DescriptionI'm noticing some potential incorrect behavior in cmake when working with add_custom_command and multiple output files. I've been able to isolate the problem to a minimal example (see below). It seems that when I have two output files specified in my add_custom_command, the second output file's upstream dependencies are not being tracked correctly in some cases. The cmake documentation clearly mentions that multiple output files are allowed. What's interesting here is that swapping the order of the output files causes different behavior, suggesting that the first OUTPUT file is being treated differently.

(Crossposted here: http://stackoverflow.com/questions/24416133/cmake-add-custom-command-issue-with-multiple-output-files [^])
Steps To ReproduceExample CMakeLists.txt:

cmake_minimum_required(VERSION 2.8)

add_library(mybaz baz.cpp)

add_custom_command(
  OUTPUT baz2.cpp
  COMMAND cp baz.cpp baz2.cpp
  DEPENDS baz.cpp
  COMMENT "Copying baz.cpp to baz2.cpp")

add_custom_target(mytarget
  DEPENDS baz2.cpp
  COMMENT "Running mytarget")

add_dependencies(mybaz mytarget)

add_custom_command(
  OUTPUT bar.cpp baz.cpp
  COMMAND cat a.txt > bar.cpp
  COMMAND cat a.txt > baz.cpp
  DEPENDS a.txt
  COMMENT "Generating bar.cpp and baz.cpp")

======================================================

Below are the commands that I run:

> touch a.txt
> cmake .
    ...snip... (configuration runs fine)
> make
Scanning dependencies of target mytarget
[ 20%] Generating bar.cpp and baz.cpp
[ 40%] Copying baz.cpp to baz2.cpp
[ 60%] Running mytarget
[ 60%] Built target mytarget
Scanning dependencies of target mybaz
[ 80%] Building CXX object CMakeFiles/mybaz.dir/baz.cpp.o
Linking CXX static library libmybaz.a
[100%] Built target mybaz
  (everything looks good)

> touch a.txt
> make
[ 20%] Generating bar.cpp and baz.cpp
[ 40%] Running mytarget
[ 60%] Built target mytarget
Scanning dependencies of target mybaz
[ 80%] Building CXX object CMakeFiles/mybaz.dir/baz.cpp.o
Linking CXX static library libmybaz.a
[100%] Built target mybaz
  (I seem to be missing the 'Copying baz.cpp to baz2.cpp' line)

> make
[ 20%] Copying baz.cpp to baz2.cpp
[ 40%] Running mytarget
[ 60%] Built target mytarget
[100%] Built target mybaz
  ( The 'Copying baz.cpp to baz2.cpp' executes this time )
Additional Information
TagsNo tags attached.
Relationships
Attached Filestxt console_output_ubuntu_14_04_cmake_2_8_12_2.txt (2,558) 2014-12-04 11:41
https://public.kitware.com/Bug/file/5310/console_output_ubuntu_14_04_cmake_2_8_12_2.txt
Issue History
Date ModifiedUsernameFieldChange
2014-08-29 13:11Vijay PradeepNew Issue
2014-09-18 12:36ShootfastNote Added: 0036825
2014-11-28 23:17Rongcui DongNote Added: 0037312
2014-12-04 11:41Vijay PradeepFile Added: console_output_ubuntu_14_04_cmake_2_8_12_2.txt
2014-12-04 11:48Vijay PradeepNote Added: 0037382
2014-12-04 15:06Rongcui DongNote Added: 0037388
2014-12-04 15:13Brad KingNote Added: 0037389
2014-12-04 15:13Brad KingAssigned To => Brad King
2014-12-04 15:13Brad KingStatusnew => assigned
2014-12-04 15:13Brad KingTarget Version => CMake 3.2
2014-12-08 09:02Brad KingNote Added: 0037404
2014-12-12 11:22Brad KingStatusassigned => resolved
2014-12-12 11:22Brad KingResolutionopen => fixed
2014-12-12 11:22Brad KingFixed in Version => CMake 3.2
2014-12-12 12:12Vijay PradeepNote Added: 0037447
2015-03-06 15:35Brad KingNote Added: 0038168
2015-03-06 15:35Brad KingStatusresolved => assigned
2015-03-06 15:35Brad KingResolutionfixed => open
2015-03-06 15:35Brad KingFixed in VersionCMake 3.2 =>
2015-03-06 15:39Brad KingNote Added: 0038169
2015-03-06 15:42Brad KingNote Added: 0038170
2015-03-06 18:14Brad KingNote Edited: 0038170bug_revision_view_page.php?bugnote_id=38170#r1722
2015-03-06 20:00Brad KingNote Edited: 0038170bug_revision_view_page.php?bugnote_id=38170#r1723
2015-03-09 09:43Brad KingStatusassigned => resolved
2015-03-09 09:43Brad KingResolutionopen => fixed
2015-03-09 09:43Brad KingFixed in Version => CMake 3.2
2015-03-09 09:44Brad KingFixed in VersionCMake 3.2 => CMake 3.2.1
2015-03-09 09:44Brad KingTarget VersionCMake 3.2 => CMake 3.2.1
2015-11-02 09:13Robert MaynardNote Added: 0039723
2015-11-02 09:13Robert MaynardStatusresolved => closed

Notes
(0036825)
Shootfast   
2014-09-18 12:36   
Hi, just reporting that I am also experiencing this bug on cmake 3.0.0.
(0037312)
Rongcui Dong   
2014-11-28 23:17   
Not reproduced on cmake version 2.8.12.2 under Ubuntu 14.04
(0037382)
Vijay Pradeep   
2014-12-04 11:48   
Hi Rongcui, I just repeated the posted 'steps to reproduce' on Ubuntu 14.04 with CMake 2.8.12.2, and I am still seeing the error. I've also uploaded my full console output from this test for further inspection at console_output_ubuntu_14_04_cmake_2_8_12_2.txt.

I'm not sure why we would be seeing different outcomes when we're running the same OS and CMake. I think it would be insightful to compare your console output the the one I just uploaded. If you have a moment, could you please rerun the experiment and upload it? Thanks!
(0037388)
Rongcui Dong   
2014-12-04 15:06   
Wait, I think I misunderstood your output. Yes, it behaves exactly like your post. I missed that "Copying" part.
(0037389)
Brad King   
2014-12-04 15:13   
I can reproduce this too.

You're correct that the first output is being treated specially by the Makefile generator. I'm not sure why things were done that way. Instead the multiple output rules should list all outputs on the left hand side of the make rule.

I'm working on a fix.
(0037404)
Brad King   
2014-12-08 09:02   
Fixed and test added:

 Xcode: Fix rebuild with multiple custom command outputs
 http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=8a4c6d2d [^]

 Makefile: Fix rebuild with multiple custom command outputs
 http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=644b4688 [^]

 Tests: Cover rebuild with multiple custom command outputs
 http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=65ea5eb7 [^]

 Makefile: Workaround Borland Make bug with multiple outputs
 http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=6c67b816 [^]
(0037447)
Vijay Pradeep   
2014-12-12 12:12   
@(Brad King): Thanks for the fix! This will definitely help streamline users' CMake experiences when trying to put together and debug complex CMake projects.
(0038168)
Brad King   
2015-03-06 15:35   
The fixes in 0015116:0037404 caused a major regression:

 Wrong behavior with 3.2.0-rc2
 http://thread.gmane.org/gmane.comp.programming.tools.cmake.user/51919 [^]

Using the style

out1 out2: depends...
        commands...


is actually just equivalent to

out1: depends...
        commands...
out2: depends...
        commands...


so in parallel builds the commands run multiple times at once.
(0038169)
Brad King   
2015-03-06 15:39   
Re 0015116:0038168: This is likely the cause of this report too:

 Parallel build of webkitgtk4 fails with cmake 3.2
 https://bugzilla.redhat.com/show_bug.cgi?id=1199360 [^]
(0038170)
Brad King   
2015-03-06 15:42   
(edited on: 2015-03-06 20:00)
Re 0015116:0038168: I've drafted the following fix:

 Makefile: Fix multiple custom command outputs regression
 http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=66a9c90c [^]

which will be included in 3.2 if it passes nightly testing, and will otherwise be revised.
(0039723)
Robert Maynard   
2015-11-02 09:13   
Closing resolved issues that have not been updated in more than 4 months.