Re: [OE-core] [PATCH] distro/include: Add yocto-space-optimize, disabling debugging for large components

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Thu, 2024-07-11 at 12:10 +0000, Ross Burton via lists.openembedded.org wrote:
> On 11 Jul 2024, at 10:30, Richard Purdie via lists.openembedded.org <richard.purdie=linuxfoundation.org@lists.openembedded.org> wrote:
> > 
> > +DEBUG_FLAGS:remove:pn-llvm = "-g"
> > +DEBUG_FLAGS:remove:pn-qemu = "-g"
> > +DEBUG_FLAGS:remove:pn-openssl = "-g”
> 
> This would be difficult to undo if the user did actually want debug symbols, right?
> 
> This :removes -g (so you can’t :append it back) from the target flags:
> 
> DEBUG_FLAGS ?= "-g -feliminate-unused-debug-types ${DEBUG_PREFIX_MAP}"
> FULL_OPTIMIZATION = "-O2 -pipe ${DEBUG_FLAGS}"
> DEBUG_OPTIMIZATION = "-Og ${DEBUG_FLAGS} -pipe"
> SELECTED_OPTIMIZATION = "${@d.getVar(oe.utils.vartrue('DEBUG_BUILD', 'DEBUG_OPTIMIZATION', 'FULL_OPTIMIZATION', d))}”
> TARGET_CFLAGS = "${TARGET_CPPFLAGS} ${SELECTED_OPTIMIZATION}”
> 
> So with this there’s no obvious way to get symbols for target llvm/qemu/openssl, setting DEBUG_BUILD=1 still won’t actually pass -g. The user would have to know to do eg CFLAGS += “-g”.
> 
> I’ll note that webkitgtk3 has approached this problem already and settled on this:
> 
> DEBUG_FLAGS:append = "${@oe.utils.vartrue('DEBUG_BUILD', '', ' -g1', d)}"
> 
> So -g1 (minimal but functional debugging info) unless DEBUG_BUILD enabled.
> 
> I’m fairly against removing _all_ debug symbols for these recipes in default builds, although I’d certainly be happy with -g1 as a compromise between space saving and utility.

I agree that the remove is too hard to undo so we can't use this
approach. We probably need to parameterise it in DEBUG_FLAGS since
we're likely to need to do this more frequently.

I do still think we should drop -g entirely for llvm though as the
debug info is just too large even at -g1. I'm particularly keen to keep
the package sizes down which keeps the sstate object size down too,
making builds from sstate better over the network.

Cheers,

Richard