[bug#54780] [PATCH] gnu: lttng-ust: Fix dependencies.

[Maxime Devos <maximedevos@telenet.be>]

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Olivier Dion schreef op vr 08-04-2022 om 13:17 [-0400]:
> --------------------
> (modify-phases %standard-phases
>          (add-after 'patch-source-shebangs 'patch-source-headers
>            (lambda* (#:key inputs #:allow-other-keys)
>              (substitute* (find-files "./include" ".h")
>                (("<(urcu/(compiler|pointer|arch|system|uatomic|config|list|tls-compat|debug|ref|rculist).h)>" _ letters _)
>                 (format #f "<~a>"
>                         (search-input-file inputs
>                                            (string-append "include/" letters))))))))

This is for the lttng-ust package, right?
The idea was to do this in a post-install phase of liburcu.

> --------------------
> 
> this seems to build the package correctly and also change the RCU
> headers for lttng-ust.  However, liburcu also include some architecture
> specific headers.  So I get the following error while compiling my
> program:
> 
> --------------------
> In file included from /gnu/store/5qk5mmffc1m9cla71jywn0qz03bk6yhi-profile/include/lttng/urcu/pointer.h:14,
>                  from /gnu/store/5qk5mmffc1m9cla71jywn0qz03bk6yhi-profile/include/lttng/tracepoint-rcu.h:11,
>                  from /gnu/store/5qk5mmffc1m9cla71jywn0qz03bk6yhi-profile/include/lttng/tracepoint.h:13,
>                  from tracepoint.h:10,
>                  from tracepoint.c:4:
> /gnu/store/25nlsljfziysgbhhj9nhwfm4qn5h4b71-liburcu-0.13.1/include/urcu/arch.h:65:10: fatal error: urcu/arch/x86.h: No such file or directory
>    65 | #include <urcu/arch/x86.h>
>       |          ^~~~~~~~~~~~~~~~~
> compilation terminated.
> --------------------
> 
> How could this be fix?   That would require to modify the inputs no?

I suggest moving the post-unpack substitute* phase from lttng-ust to a
post-install phase in liburcu.  That way, urcu/arch.h can be patched to
use an absolute file name.

Also, this ...

 (urcu/(compiler|pointer|arch|system|uatomic|config|list|tls compat|debug|ref|rculist).h)>

seems rather fragile and could easily break on future updates of lttng-ust.
The idea of the 'absolute-inclusions.scm' file I sent, is to automate things.
More concretely, my suggestion is to:

  * add absolute-inclusions.scm to the Guix repo, in guix/build
  * modify liburcu to:

  (package
    (name "liburcu")
    [...]
    (arguments
      (list #:imported-modules `(,@%gnu-build-system-modules (guix build absolute-inclusions))
            #:modules '((guix build gnu-build-system)
                        (guix build absolute-inclusions))
            #:phases
            #~(modify-phases %standard-phases
                (add-after 'install 'absolute-inclusions absolute-inclusions)))))

Greetings,
Maxime.

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