Bug#964728: gtk-doc-tools: gtkdoc-scangobj fails in mipsel / Loongson when building webkit2gtk

[smcv at debian.org]

On Thu, 09 Jul 2020 at 17:42:35 +0200, Alberto Garcia wrote:
> the mipsel build of webkit2gtk is failing because of gtkdoc-scangobj:
...
> This is only happening on the mipsel builds, and I cannot reproduce
> the problem in eller.debian.org. Adrian Bunk says it fails on the
> Loongson buildds but succeeds on the others.

gtkdoc-scangobj works by compiling a small C program that it uses
to introspect GObject types. According to the build log, that program
exited with status -6 (which is probably Python's representation of it
being killed by signal 6, which is SIGABRT?) with no output.

The Loongson 3A "is known for having an FPU bug" (see #959845) -
perhaps that could be related, if webkit2gtk contains GObject types
with G_TYPE_FLOAT or G_TYPE_DOUBLE values? I'm not sure what individual
packages can do about this, or why we are using known-faulty CPUs on
official buildds.

This is likely to be "won't fix" (or rather "can't fix") for
gtk-doc-tools, unless someone with a suitably faulty FPU can reproduce
the bug and figure out what is going on.

Workaround: instead of

----8<----
ifneq (,$(filter nodoc,$(DEB_BUILD_OPTIONS)))
	EXTRA_CMAKE_ARGUMENTS += -DENABLE_GTKDOC=OFF
else
	EXTRA_CMAKE_ARGUMENTS += -DENABLE_GTKDOC=ON
endif
----8<----

webkit2gtk could use something like

----8<----
binaries := $(shell dh_listpackages)

ifneq (,$(filter %-doc,$(binaries)))
	EXTRA_CMAKE_ARGUMENTS += -DENABLE_GTKDOC=OFF
else
	EXTRA_CMAKE_ARGUMENTS += -DENABLE_GTKDOC=ON
endif
----8<----

together with

----8<----
Package: libwebkit2gtk-4.0-doc
Build-Profiles: <!nodoc>
----8<----

so that you don't run gtk-doc in architecture-specific builds, only in
builds that include Architecture: all. That would also be faster, and you
might be able to move gtk-doc-tools from Build-Depends to
Build-Depends-Indep (usually you can for Meson, but not for Autotools
because it's needed at dh_autoreconf time; I don't know which category
CMake falls into).

    smcv