Compiling LO for lcov/gcov code coverage fails (gb_GCOV=YES)

[Maarten Hoes]

On Tue, May 17, 2022 at 11:42 AM Michael Stahl <mst at libreoffice.org> wrote:

> On 13.05.22 16:42, Maarten Hoes wrote:
> > So to sum it up, with only gcc installed, the gcov build works if I
> modify :
> >
> > external/expat/ExternalProject_expat.mk
> > external/liborcus/ExternalProject_liborcus.mk
> >
> > and add :
> >
> > CFLAGS += -fprofile-arcs -ftest-coverage
> > CXXFLAGS += -fprofile-arcs -ftest-coverage
> > LDFLAGS += -fprofile-arcs -lgcov
> >
> > to the top of them. Of course, that does not seem to be a proper
> > permanent solution to the issue: the question remains why these *FLAGS
> > don't end up in these 2 files when you specify 'gb_GCOV=YES make'.
>
> also, there is another problem: setting global variables like this will
> affect *all* makefiles, which may or may not be what you intend - it's
> certainly bad style to do it from a local makefile.
>

What basically is intended, is that all of LibreOffice gets compiled with
gcov code coverage magic included, which I believe indeed translates to
'all' makefiles. But I already got the idea that the way I modified those
makefiles was a terrible way to do things; it's just that this seemed the
quickest/easiest way (from my point of view, considering my inexperience
with makefiles) to test things out, without having to take the deep dive
into the build system and the makefiles.



>
> > Pointers to where I should start looking in the build system in an
> > attempt to troubleshoot things are appreciated. I found the point where
> > the flags are supposed to be set conditionally in lines 112-117 in
> > 'solenv/gbuild/platform/com_GCC_defs.mk' , but don't really know how to
> > proceed from there. Perhaps the variables
> > "gb_CFLAGS_COMMON/gb_CXXFLAGS_COMMON/gb_LinkTarget_LDFLAGS" are not used
> > in the right places, or overwritten with something else ?
>
> the global *FLAGS variables should be in config_host.mk, set from
> configure script.
>
> often the best way to set *FLAGS locally is to pass them to the
> configure invocation in an ExternalProject*.mk, taking care not to mess
> up make's terrible syntax (like \ EOL escaping).
>
> but the ExternalProject_expat.mk doesn't set *FLAGS variables - so the
> ones from config_host.mk should be in effect - and the
> ExternalProject_liborcus.mk sets them by "liborcus_CXXFLAGS=$(CXXFLAGS)
> ..." so effectively appending.
>
> ah, in LinkTarget.mk in the gb_GCOV case no CXXFLAGS are set, only
> gb_CXXFLAGS_COMMON etc - that explains the problems you see, these are
> only used for gbuild's native LinkTargets.
>
>
Thanks for that bit. The fact that I still find it slightly difficult to
follow only underscores my inability to read or modify makefiles (properly).



> if you want coverage in externals, it might make sense to pass properly
> set *FLAGS variables to LO's configure - this will then override
> gbuild's optimization and debugging flags, so include "-g" in case it's
> needed for the converage (i don't know how that works).
>

What I got from that, was that I need to do *both* of the following :

set CFLAGS/CXXFLAGS/LDFLAGS for gcov on the ./autogen commandline :
CFLAGS='-fprofile-arcs -ftest-coverage' CXXFLAGS='-fprofile-arcs
-ftest-coverage' LDFLAGS='-fprofile-arcs -lgcov' ./autogen.sh

and set gb_GCOV=YES on the make commandline :
gb_GCOV=YES make

which gives me a successful build (!) (without having to modify any
makefiles).


Thanks.


- Maarten
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