Re: [libgpiod][PATCH 1/1] dbus: manager: fix linker not finding libgpiod.so

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Thu, Feb 6, 2025 at 12:46 AM Börge Strümpfel
<boerge.struempfel@xxxxxxxxx> wrote:
>
> Hi Bart,
>
> While preparing a patch to add gpio-manager to mainline Buildroot, I
> encountered this issue again. That is, I can successfully compile the
> gpio-manager manually (using autotools/gcc/ld provided by ubuntu 2024) however,
> when using the Buildroot infrastructure, I get a compiler error, stating that
> the libgpiod.so.3 cannot be found.
>
> After further investigation, I'm increasingly unsure on how the
> libgpiod.so.3 is supposed to be found by the linker in the first place:
>
> From what I see, gpio-manager depends on:
> - bindings/glib/libgpiod-glib
> - dbus/lib/libgpiodbus

Correct.

> - lib/libgpiod

This one is an indirect dependency, it's already pulled in by libgpiod-glib.so.

>
> However, I see no direct reference in dbus/manager/Makefile.am, nor can I see
> an indirect reference via the Makefile.am files used to generate:
> - bindings/glib/libgpiod-glib.la
> - dbus/lib/libgpiodbus.la
>
> Am I missing something obvious?
>

These are generated in different directories, the Makefiles in there
take care of this.

> Furthermore upon review, I believe the solution I proposed last October was
> flawed - I should have used:
> LDADD += $(top_builddir)/lib/libgpiod.la

On Ubuntu, I see that gpio-manager is only linked against
libgpiod-glib.so and libgpiodbus.so. However if I cross-compile on
yocto, it's linked against libgpiod.so as well. I don't know exactly
what the differences in linker setup are but yocto is able to find
libgpiod without problems. Before we add an unnecessary flag, may I
suggest looking into how yocto does the linking?

Bart