[Buildroot] [PATCH 1/1] package/pkg-meson: handle b_pie

[Yann E. MORIN]

Fabrice, All,

Meson experts, questions for you below!

On 2021-05-29 11:41 +0200, Fabrice Fontaine spake thusly:
> Le sam. 29 mai 2021 à 11:21, Yann E. MORIN <yann.morin.1998 at free.fr> a
> écrit :
> > On 2021-05-29 11:09 +0200, Yann E. MORIN spake thusly:
> > > On 2021-05-28 21:17 +0200, Fabrice Fontaine spake thusly:
[--SNIP--]
> > > > diff --git a/package/pkg-meson.mk b/package/pkg-meson.mk
> > > > index a57820d4d2..a55063d58e 100644
> > > > --- a/package/pkg-meson.mk
> > > > +++ b/package/pkg-meson.mk
> > > > @@ -91,6 +91,7 @@ define $(2)_CONFIGURE_CMDS
> > > >             --default-library=$(if
> > > >             $(BR2_STATIC_LIBS),static,shared) \
> > > >             --buildtype=$(if $(BR2_ENABLE_DEBUG),debug,release)
> > > >             \
> > > >             --cross-file=$$($$(PKG)_SRCDIR)/build/cross-compilation.conf
> > > >             \
> > > > +           -Db_pie=$(if
> > > > $(BR2_TOOLCHAIN_SUPPORTS_PIE),true,false) \
> > Given a later patch that arrived in parallel, it turns out this
> > patch
> > was not correct, and that we still have a bit of interrogation on
> > that,
> > so I've reverted it, sorry. I'll keep an eye on the discussions...
> I think that the second version of this patch (i.e. always disabling
> b_pie through command line) is the best option because:
> - PIE is already enabled by the toolchain-wrapper:
> hardening-check
> output/build/pipewire-0.3.26/build/spa/plugins/audioconvert/benchmark-resample
> output/build/pipewire-0.3.26/build/spa/plugins/audioconvert/benchmark-resample:
>  Position Independent Executable: yes

OK, so PIE is indeed applied when building, good.

> - Enabling PIE in two different places is not future-proof and is not
> done in any other infrastructures (autotools, cmake, etc.).

Yeah, that makes perfect sense.

> I think
> this is also the reason why strip is unconditionally disabled in the
> command line (it is already handled in Makefile.in)

Yeah, I know about strip. However, my question for the meson experts in
the room, is: should we leave that (strip, b_pie) on the command line,
or should we have them in the cross-compilation file?

Additionaly, the machine-files documentation [0] lists pkg_config_path
as being part of the builtin options, so shouldn't we also push that
into the cross-compilation file?

As of today, we have two places where we push meson options: the command
line, and the cross-compilation file. To further Fanrice's argument:
having two places where we push options is not very consistent and
future-proof.

Basically, that would give a patch like (@HOST_DIR@ is already replaced):

    diff --git a/package/meson/cross-compilation.conf.in b/package/meson/cross-compilation.conf.in
    index 37b49eea3b..942f68f008 100644
    --- a/package/meson/cross-compilation.conf.in
    +++ b/package/meson/cross-compilation.conf.in
    @@ -13,6 +13,9 @@ g-ir-compiler = '@STAGING_DIR@/usr/bin/g-ir-compiler'
     g-ir-scanner = '@STAGING_DIR@/usr/bin/g-ir-scanner'
     
     [built-in options]
    +b_pie = false
    +strip = false
    +build.pkg_config_path = '@HOST_DIR@/lib/pkgconfig'
     c_args = [@TARGET_CFLAGS@]
     c_link_args = [@TARGET_LDFLAGS@]
     cpp_args = [@TARGET_CXXFLAGS@]
    diff --git a/package/pkg-meson.mk b/package/pkg-meson.mk
    index 1857450564..87cf0e3dd7 100644
    --- a/package/pkg-meson.mk
    +++ b/package/pkg-meson.mk
    @@ -91,9 +91,6 @@ define $(2)_CONFIGURE_CMDS
     		--default-library=$(if $(BR2_STATIC_LIBS),static,shared) \
     		--buildtype=$(if $(BR2_ENABLE_DEBUG),debug,release) \
     		--cross-file=$$($$(PKG)_SRCDIR)/build/cross-compilation.conf \
    -		-Db_pie=false \
    -		-Dstrip=false \
    -		-Dbuild.pkg_config_path=$$(HOST_DIR)/lib/pkgconfig \
     		$$($$(PKG)_CONF_OPTS) \
     		$$($$(PKG)_SRCDIR) $$($$(PKG)_SRCDIR)/build
     endef

As far as I can tell from the documentation, this really seems like this
should be what we want to do in Buildroot, because that way, these
settings will also be used for the SDK, or for building manually outside
of Buildroot...

So, what's your thoughts about that?

Regards,
Yann E. MORIN.

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