Re: [Valgrind-developers] Out of tree build

[Philippe W. <phi...@sk...>]

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

Philippe