[cmake-developers] ExternalProject: Use native paths as substitute for directory tokens

Kislinskiy, Stefan s.kislinskiy at Dkfz-Heidelberg.de
Wed Aug 26 03:35:24 EDT 2015


Would you prefer to have a switch for each *_DIR variable for all target steps, or a common switch but for each target step, like the new USE_TERMINAL switches in the master?
________________________________________
Von: CHEVRIER, Marc [marc.chevrier at sap.com]
Gesendet: Mittwoch, 26. August 2015 08:49
An: David Cole; Kislinskiy, Stefan
Cc: cmake-developers at cmake.org
Betreff: Re: [cmake-developers] ExternalProject: Use native paths as substitute for directory tokens

I agree with David.

Offering the possibility to manage native paths in an easy way is a very good enhancement (Today, I rely on some specific actions when I am on Win32 to manage native path for ONE specific step of ExternalProject) BUT, offering only the alternative to have NONE or ALL paths in native form is, by far, too restrictive.
So I am for the solution providing new patterns as alternative to current ones to manage native paths, i.e. Adding <*_NATIVE_DIR> for all already available <*_DIR> patterns.

Marc



On 25/08/15 17:31, "cmake-developers on behalf of David Cole via cmake-developers" <cmake-developers-bounces at cmake.org on behalf of cmake-developers at cmake.org> wrote:

>I'm going to let other CMake developers chime in on this one.
>
>It's better than the first patch, because it's opt-in, and you have to
>add something to get "different than previous" behavior, but I'm still
>of the opinion that this is very command specific, and you won't
>always want all _DIR references as native. In my opinion, it's better
>left to the person constructing the ExternalProject_Add call. But I am
>curious to hear other CMake devs give their opinions.
>
>
>David C.
>
>
>
>On Tue, Aug 25, 2015 at 3:18 AM, Kislinskiy, Stefan
><s.kislinskiy at dkfz-heidelberg.de> wrote:
>> Dear CMake developers,
>>
>> any thoughts on the fix? :)
>>
>> Best regards,
>> Stefan Kislinskiy
>> ________________________________________
>> Von: cmake-developers [cmake-developers-bounces at cmake.org] im Auftrag von Kislinskiy, Stefan [s.kislinskiy at dkfz-heidelberg.de]
>> Gesendet: Freitag, 21. August 2015 23:56
>> An: David Cole; James Johnston
>> Cc: cmake-developers at cmake.org
>> Betreff: Re: [cmake-developers] ExternalProject: Use native paths as substitute for directory tokens
>>
>> What do you think about the new patch I attached to this mail? It adds an option NATIVE_DIR_TOKENS to ExternalProjects_Add. I also attached a CMake script file which tests/shows this feature.
>>
>> Stefan Kislinskiy
>> ________________________________________
>> Von: cmake-developers [cmake-developers-bounces at cmake.org] im Auftrag von David Cole via cmake-developers [cmake-developers at cmake.org]
>> Gesendet: Donnerstag, 20. August 2015 23:20
>> An: James Johnston
>> Cc: cmake-developers at cmake.org
>> Betreff: Re: [cmake-developers] ExternalProject: Use native paths as substitute for directory tokens
>>
>> It's exactly what I am concerned about:
>>
>> You're asking to change the behavior of something for EVERYONE to
>> solve a problem which you have encountered. If you change it the way
>> you have proposed, you will cause problems for others. It has worked
>> the way it is now since ExternalProject_Add was introduced in CMake
>> 2.8. Changing it unconditionally the way you propose is simply not
>> feasible for backwards compatibility.
>>
>> I think commands that take native paths ought NOT to use the <*_DIR>
>> replacement values, and instead, ought to pass in variables that
>> contain the native paths in the first place.
>>
>>
>> David C.
>>
>>
>>
>> On Thu, Aug 20, 2015 at 2:58 PM, James Johnston
>> <johnstonj.public at codenest.com> wrote:
>>> Hi,
>>>
>>> Funny you are mailing the list about this, since I just ran into this same issue today building something totally different from Boost...  In this case it's a build tool that thinks the "/U" in "C:/Users" is a new command line argument, that isn't recognized - and then the subsequent "s" also ends up unrecognized... and it all fails...  And it has nothing to do with the working directory, so _Add_Step(WORKING_DIRECTORY) isn't a possible workaround for me.
>>>
>>> I think the issue with globally making this change to the existing tokens is that there could be some external tool/program that is EXPECTING to get CMake paths, not native paths.  Who knows?  I am guessing that is what David Cole was concerned about.
>>>
>>> Maybe the right answer is to introduce some NEW tokens while leaving the behavior of the old ones unchanged.  E.g. <BINARY_DIR_NATIVE> etc.  It would be good if the patch updates the documentation of ExternalProject and clearly states the path format of <BINARY_DIR> vs <BINARY_DIR_NATIVE>.  Then the user can pick whichever one suits them best, depending on the tool being invoked.
>>>
>>> Furthermore, sometimes <BINARY_DIR_NATIVE> still needs to be replaced with a CMake path, not native path.  For example, if the token is being found in a property like WORKING_DIRECTORY that eventually gets passed to add_custom_command(WORKING_DIRECTORY) then I'm guessing still has to be a CMake path.  I am guessing this is what David Cole was also concerned about.
>>>
>>> I still think your original method of building Boost is a bit unusual and would be better served by _Add_Step with a custom working directory - because that's the publicly documented/standard way of changing the working directory, but that is up to you.  :)
>>>
>>> Best regards,
>>>
>>> James Johnston
>>>
>>>
>>> ---- On Thu, 20 Aug 2015 14:37:08 +0000  Stefan Kislinskiy <s.kislinskiy at Dkfz-Heidelberg.de> wrote ----
>>>
>>>  > Hi,
>>>  >
>>>  > thank you for our suggestions. I am aware that I can solve my example differently and that it might look not directly connected the proposal, but well, it is an example just to show a single case and why it matters. :) I did not want to discuss the example itself. Working around here would just resolve a symptom.
>>>  >
>>>  > My point is the overall problem that would persist: A big part of ExternalProject is to issue commands for predefined and custom steps. Those commands are supposed to be executed by the shell/command line. According to the documentation and the source code of ExternalProject, directory tokens are mainly supposed to be replaced in commands. It is my understanding, that it is a bug, if CMake isn't able to assemble these commands correctly. This would include usage of the correct path style of the OS for shell/command line commands. As directory tokens are replaced internally right before a shell/command line command is assembled, I can't see why this would be kind of "API-breaking". You cannot interfere in your CMake code with these internal replacements.
>>>  >
>>>  > Therefore I would still prefer my solution as it is pretty simple without adding even more features to ExternalProject and in my opinion without breaking code in the wild. It is a true bug fix instead of a feature request for working directories, which is a different topic that just coincidentally arised because of my specific example I guess. The features you described wouldn't fix the actual bug.
>>>  >
>>>  > As you were not sure if my approach would even fix my problems: It does of course and this is what I am currently doing and what I tested extensively before creating the patch. :) Regarding your quote from the add_custom_command documentation I can tell you that this is how things are currently done in ExternalProject and always were as far as I know, for example (from ExternalProject.cmake):
>>>  >
>>>  >   add_custom_command(
>>>  >     OUTPUT ${stamp_file}
>>>  >     BYPRODUCTS ${byproducts}
>>>  >     COMMENT ${comment}
>>>  >     COMMAND ${command}
>>>  >     COMMAND ${touch}
>>>  >     DEPENDS ${depends}
>>>  >     WORKING_DIRECTORY ${work_dir}
>>>  >     VERBATIM
>>>  >     )
>>>  >
>>>  > Best regards,
>>>  > Stefan
>>>  >
>>>  >
>>>  > -----Original Message-----
>>>  > From: cmake-developers [mailto:cmake-developers-bounces at cmake.org] On Behalf Of James Johnston
>>>  > Sent: Donnerstag, 20. August 2015 15:37
>>>  > To: cmake-developers at cmake.org
>>>  > Subject: Re: [cmake-developers] ExternalProject: Use native paths as substitute for directory tokens
>>>  >
>>>  > > -----Original Message-----
>>>  > > From: cmake-developers [mailto:cmake-developers-bounces at cmake.org]
>>>  > > On Behalf Of Kislinskiy, Stefan
>>>  > > Sent: Thursday, August 20, 2015 09:02
>>>  > > To: David Cole
>>>  > > Cc: cmake-developers at cmake.org
>>>  > > Subject: Re: [cmake-developers] ExternalProject: Use native paths as
>>>  > > substitute for directory tokens
>>>  > >
>>>  > > Hi David,
>>>  > >
>>>  > > Example excerpt (it is not possible to change the working directory
>>>  > > for
>>>  > the
>>>  > > CONFIGURE_COMMAND as it is fixed to the BUILD_DIR, which might not be
>>>  > > sufficient):
>>>  >
>>>  > This doesn't really directly have to do with your proposal, but what if an option was added to change the working dir of the CONFIGURE_COMMAND?  E.g.
>>>  > WORKING_DIRECTORY_CONFIGURE.  And suppose you'd have it recognize the various tags like <SOURCE_DIR>, etc.  This might be useful to add to other steps as well, and would be more portable than your solution which is using cmd.exe-specific commands.  You'd want to audit for any resulting breakage (e.g. does ExternalProject make assumptions that the working directory of CONFIGURE is always the binary dir? - e.g. a relative path being used somewhere.  And probably only allow specification of WORKING_DIRECTORY_CONFIGURE if a CONFIGURE_COMMAND was also specified, as the built-in commands certainly assume the default working dir.)
>>>  >
>>>  > In your situation though, I'm not sure it's strictly needed.  From your sample, it looks like you're building boost.  In your case what if you:
>>>  >
>>>  >  * Use ExternalProject_Add_Step to bootstrap.  You can specify a WORKING_DIRECTORY here.  Note one problem: you can't do out of source build of b2, which breaks user expectations.
>>>  >  * Then use ExternalProject_Add_Step to build Boost.
>>>  >
>>>  > Yes, using _Add_Step is somewhat of a workaround, but in this case, I've found it wasn't much of a burden at all.  In fact the only case I can think of where it WOULD be a burden would be if the configure step is CMake.  But then you wouldn't need to change the working directory; changing it would break CMake.  In practice nobody will want to change WORKING_DIRECTORY unless it's a custom command and then it's easy to use _Add_Step anyway.
>>>  > That said, it might still be considered a little undesired and so maybe my proposal above would be a better way to handle it.
>>>  >
>>>  > Corrections from maintainers and others on the above commentary are welcome...
>>>  >
>>>  > >
>>>  > > set(bootstrap_cmd "<SOURCE_DIR>/bootstrap${shell_ext}"
>>>  > > ${bootstrap_toolset})
>>>  > >
>>>  > > if(WIN32)
>>>  > >   set(bootstrap_cmd pushd "<SOURCE_DIR>" COMMAND ${bootstrap_cmd}
>>>  > > COMMAND popd)
>>>  > > endif()
>>>  > >
>>>  > > ExternalProject_Add(Boost
>>>  > >   ...
>>>  > >   CONFIGURE_COMMAND ${bootstrap_cmd}
>>>  > >   ...
>>>  > > )
>>>  >
>>>  > From add_custom_command:  "If more than one COMMAND is specified they will be executed in order, but not necessarily composed into a stateful shell or batch script."
>>>  >
>>>  > So I am not sure your approach will work for you even if you fix the issue with path slashes.
>>>  >
>>>  > James
>>>  >
>>>
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>Powered by www.kitware.com
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>
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