[OE-core] TARGET_CFLAGS for non-target builds

[Christopher Larson]

Target_cflags is an exported variable. It affects the checksums of every
task. Not ideal, but that's how it is today.
On Mon, Feb 8, 2016 at 5:10 PM Andre McCurdy <armccurdy at gmail.com> wrote:

> On Mon, Feb 8, 2016 at 4:01 PM, Mark Hatle <mark.hatle at windriver.com>
> wrote:
> > On 2/8/16 5:43 PM, Andre McCurdy wrote:
> >> On Mon, Feb 8, 2016 at 3:00 PM, Burton, Ross <ross.burton at intel.com>
> wrote:
> >>>
> >>> On 8 February 2016 at 20:03, Andre McCurdy <armccurdy at gmail.com>
> wrote:
> >>>>
> >>>> Can you give an example? Looking at native.bbclass it seems to replace
> >>>> TARGET_CFLAGS with BUILD_CFLAGS, not manipulate it.
> >>>
> >>> Sure, so in doing a native build TARGET_CFLAGS is used.  But as
> >>> security_flags.inc was using TARGET_CFLAGS_append, the end result was
> >>> BUILD_CFLAGS appended with the security flags.
> >>
> >> Yes, for native, TARGET_CFLAGS will end up being "${BUILD_CFLAGS}
> >> ${SECURITY_CFLAGS}".
> >>
> >> However it shouldn't matter - native.bbclass sets CFLAGS to
> >> BUILD_CFLAGS, not TARGET_CFLAGS.
> >>
> >> Do you have an example where host gcc can legitimately be invoked with
> >> TARGET_CFLAGS?
> >
> > You have to remember the order of the operators.  _append says to make
> the
> > append, AFTER everything else has been evaluated (and before _remove).
> This
> > includes override behaviors.
> >
> > So if you do:
> >
> > TARGET_CFLAGS = "-deadbeef"
> > BUILD_CFLAGS = "-badc0ffee"
> > TARGET_CFLAGS_append = " -foobar"
> > TARGET_CFLAGS = "${BUILD_CFLAGS}"
> >
> > The final value of TARGET_CFLAGS is "-badc0ffee -foobar"
> >
> > Thus by changing the append to:
> >
> > TARGET_CFLAGS_append_class-target = " -foobar"
> > TARGET_CFLAGS_class-native = "${BUILD_CFLAGS}"
> >
> > In the case where the 'class-target' is the override you will get:
> >
> > TARGET_CFLAGS = "-deadbeef -foobar"
> >
> > In the case where the 'class-native' is the override you will get:
> >
> > TARGET_CFLAGS = "-badc0ffee"
>
> I'm not disputing that TARGET_CFLAGS can contain something bogus for a
> class-native build.
>
> I'm asking why does it matter?
>
> Setting TARGET_CFLAGS at all in native.bbclass is fairly recent and
> seems to be a workaround to avoid churning sstate:
>
>
> http://git.openembedded.org/openembedded-core/commit/?id=05a70ac30b37cab0952f1b9df501993a9dec70da
>
> Is that perhaps still the real reason to avoid modifying TARGET_CFLAGS
> for a native build?
>
>
> > --Mark
> --
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