generated .pc files have no prefix information

[tho-]

Generated .pc files in ros-groovy define no "prefix" variable:
% pkg-config --variable=prefix roslib

%

It is customary to define prefix, includedir, libdir, datadir etc. in .pc files, so that one is able to retrieve this information whenever needed. In ros-fuerte, .pc files were correctly defining these. Was this dropped intentionnaly?

[dirk-thomas]

In Fuerte and before the variable was mainly used to put together the other relative paths:

prefix=/opt/ros/fuerte
includedir=${prefix}/include
libdir=${prefix}/lib

Name: roscpp
Description: Description of roscpp
Version: 1.8.16
Cflags: -I${includedir}
Libs: -L${libdir} -lroscpp
Requires: cpp_common rostime rosconsole roscpp_serialization roscpp_traits std_msgs rosgraph_msgs xmlrpcpp

Since Groovy the include and library information are build differently and in this step the variables prefix, includedir and libdir where removed. It would be easily possible to readd at least the prefix variable if there is need to provide the information (or that is commonly the case for most .pc files).

For other variables like includedir and libdir it would be problematic since the .pc files might contain Cflags and Libs with various different entries and not only a single folder anymore.

[tho-]

Well, all the point of a .pc file is to be able to deliver this kind of information :) You can't decide (or know) yourself in advance what a end-user will want, so removing it is going to imped those who need the information with no benefit.
And for that matter, I was using the prefix information ;)

I'd say that most .pc files are based on the same pattern:
% cd /usr/local/lib/pkgconfig
% grep ^prefix= *.pc | wc -l
387
% ls -1 *.pc | wc -l
390

If that's easy (I think it's bascially a matter of a @(CMAKE_INSTALL_PREFIX)), why not add it back, please? :)
Or is there another way to retrieve this information?

[dirk-thomas]

No, there is no other way to retrieve that information from a package. As mentioned, I can readd the prefix for sure. But likely not the other variables.

http://linux.die.net/man/1/pkg-config mentions that Most packages define the variable "prefix". So to follow that I will readd the prefix in the next release of catkin.

[tho-]

All right, thanks! I'm fine with re-adding just "prefix" :)

Regarding the other variables, I understand your point and I understand that with the current code it's difficult to compute. But I'm not sure to get the rationale. The .pc file is not supposed to include information regarding the dependencies of a package. It must just contain the information for the package itself. So, for instance for includedir, a package is unlikely to install headers in multiple locations. It will basically install its public header in some place (e.g. $prefix/include/$package), and includedir is just that value (it's thus a bit different from Cflags). Are there any ros packages that scatter their includes among multiple directories?

[dirk-thomas]

It is only true that a package has a single include folder when it has been installed. Inside the workspace (in the devel space) it might have multiple folders: e.g. one with the hand written header inside the package source folder, one inside the devel space containing generated code of for example messages.

[tho-]

Mmm... I see. I'm really puzzled with that idea of not installing software ... but ok, this is another topic and this is not the place to discuss it.

Thanks again for the quick replies :)

[tho-]

Thanks, but "prefix" should be a variable and set with `=', like so:
prefix=@PROJECT_SPACE_DIR

[dirk-thomas]

Thanks for catching this!