Linking a package against sci-physics/root

[AstroFloyd]

I am trying to write an ebuild that will install a package that will be called sci-libs/gds-dtt-2.19.7. Its libraries need to be linked to those of the sci-physics/root package, which is in portage, so I installed v6.24.06-r1 thence. The gds-dtt installer uses autotools and its configure locates the root installation correctly, as sitting in the (unusual) path /usr/lib/root/6.24, and the root-config script, which can provide compiler flags:

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checking for root-config... /usr/lib/root/6.24/bin/root-config
checking for ROOT... checking for ROOT cling... yes
/usr/lib/root/6.24

However, when linking, the libraries are not found:

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           /usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lGui
           /usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lCore
           /usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lImt
           /usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lNet
           /usr/lib/gcc/x86_64-pc-linux-gnu/10.3.0/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -lHist
           etc...

I'm guessing I need to get the correct compiler options from root-config into my ebuild somehow, but I am not sure how to do this. (I naively tried

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CXXFLAGS="${CXXFLAGS} `root-config --cflags`"

but external commands are not allowed.) It is possible that my question boils down to "how can I call external commands to change e.g. the CXXFLAGS environment variable in an ebuild?".

The tarball for the package can be found here and I posted my current ebuild and metadata.xml. I have written ebuilds for (hopefully) all dependencies, which can be found in the AstroFloyd overlay, which can be added using e.g. app-portage/layman.

[Phoenix591]

There's probably a better way to fix this particular problem, but use the flag-o-matic eclass to manipulate *FLAGS.

[larrys]

I was thinking this could be fixed by adding

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AM_LDFLAGS = "-L$(rootlib) "

to the top-level Makefile.am. Automake also supports per-program variables like "foo_LDFLAGS". OP already has the "rootlib" variable set by configure using the "root-config" script. It just needs to be passed to Automake and added to the link step. Don't really think the ebuild is the right place to handle this.

[AstroFloyd]

Thanks for your help, I'll have a look at your suggestions. Meanwhile I also found a workaround here:

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 if [[ ${EBUILD_PHASE} != depend ]]; then
    # safely execute commands in global scope here
    CXXFLAGS="${CXXFLAGS} `root-config --cflags`"
    LDFLAGS="${LDFLAGS} `root-config --libs`"
fi

Not sure how good this practice is though...

[sam_]

Thanks for your help, I'll have a look at your suggestions. Meanwhile I also found a workaround here:

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 if [[ ${EBUILD_PHASE} != depend ]]; then
    # safely execute commands in global scope here
    CXXFLAGS="${CXXFLAGS} `root-config --cflags`"
    LDFLAGS="${LDFLAGS} `root-config --libs`"
fi

Not sure how good this practice is though...

Order of preference:
1. Do it in the build system!
2. Do it in the ebuild. You should be able to just do append-cxxflags, append-ldflags (or append-libs ideally) from flag-o-matic.eclass.
3. Do it in the environment (ew).