Re: [Valgrind-developers] Out of tree build

[Gilles C. <gil...@xe...>]

Le 19/04/2014 18:10, Philippe Waroquiers a écrit :
> On Sat, 2014-04-19 at 17:53 +0200, Gilles Chanteperdrix wrote:
>> L
>>> Can you give more information about:
>>>   what do you mean exactly by "building valgrind out of its source tree" ?
>>>   why do you want to build it out of its source tree, if building it is
>>>     working ?
>>>   which OS ?
>>>   which distribution ?
>>>   what build error/error msg/... you have without the above change ?
>>
>> Building a project "out-of-tree" is a common feature for projects using
>> the autotools, see for instance:
>>
>> http://www.gnu.org/software/automake/manual/html_node/VPATH-Builds.html
>>
>> In a nut shell, by running the configure script from a build directory
>> different from the sources directory, the program gets built in this
>> build directory instead of inside the source tree.
>>
>> The reason I use this is that it allows me to build valgrind for
>> different platforms from the same source tree, without duplicating or
>> symlinking the source tree.
>>
>> The out-of-tree builds relies on make's VPATH variable. Makefiles are
>> run from a build tree, which does not contain the sources, but make
>> looks for the dependencies in the directory mentioned in the VPATH
>> variable, and passes the complete path to make rules when the dependency
>> is found in the VPATH tree.
>>
>> So, for instance, if a foo.supp exists in /tmp/bar and /tmp/qux/Makefile
>> contains:
>>
>> DEFAULT_SUPP_FILES=foo.supp
>>
>> VPATH = /tmp/bar
>>
>> default.supp: $(DEFAULT_SUPP_FILES)
>> 	echo $<
>>
>> Running "make default.supp" in /tmp/qux will print /tmp/bar/foo.supp
>> instead of just foo.supp, IOW, the rule gets passed the full path of the
>> dependency.
>>
>> Without this change, cat $(DEFAULT_SUPP_FILES) fails because the files
>> are not found in the build tree.
>>
>> I understand if you do not want to support that feature, but since the
>> modification to get it working is a one-liner, I assumed that it was an
>> already supported feature, and that the fact that it did not work in
>> 3.9.0 was an oversight.
> Thanks for the detailed explanation above.
> It looks effectively interesting to me to be able to use one source
> tree but build it in various other directories with different configure
> setup.
> 
> My knowledge of autotools and the valgrind build system is quite
> elementary, so I cannot judge what are the implications of supporting
> this. I suppose it does not imply to use particularly recent
> versions of some tools ?
> 
> I suggest you file a wishbug in bugzilla with the above explanation
> and your patch.
> You might as well complete your patch by updating the documentations
> giving the build instructions (i.e. adding a section or a paragraph
> in README explaining how to do a out of source tree build).
> 
> Thanks for looking at this

It is done with bug 333628. Note that the attached patch is for trunk,
which required quite a few more changes.

Note that a fix similar to mine had already been proposed since 3.6.0:
https://bugs.kde.org/show_bug.cgi?id=256174

-- 
Gilles.