[Buildroot] Improving buildroot
ulf.samuelsson at atmel.com
Sat Jul 26 06:49:18 UTC 2008
> I'm new to the list, but not to linux nor the idea of cross-compiling
> under Unix.
> One of the first things I noticed was that there are a lot of braindead
> configure.ac scripts out there that don't handle cross-compilation.
> That won't be of news to anyone I don't think. The 2nd thing that I
> followed on with was that by using the appropriate --with, --without,
> --enable, --disable, and ac_cv_foo values when invoking ./configure, a
> lot of this stuff could be mitigated.
> The 2nd argument to AC_CHECK_SIZEOF() is a travesty, and there's no good
> reason for having it. It will be wrong as often as it will be right, so
> why bother having it at all?
> I also noticed that some of the buildroot makefile's don't properly
> order their targets or rely on their dependencies' ages properly, so
> that doing a "make all" followed by another "make all" doesn't, in fact,
> result in "Nothing to be done for `all'" as the result... but instead a
> lot of rules are run again for no apparent reason.
Yes, this happens from time to time, when the rules are changed.
Patches to fix this are definitely welcome.
> I try to fix these as I encounter them, but I've not been very diligent
> about noting them. I'll try to do better, and indeed to post my patches
> to makefiles as I find them.
> So... getting back to the first issue... incorrect detection of the
> target environment's characteristics when cross-compiling... Why don't
> we just capture most of this into a Makefile statically?
> In the astlinux project, for instance, we have in one of our Makefiles
> something like:
> LINUX_VERSION_MAJOR:=$(shell echo $(LINUX_VERSION) | cut -d. -f1)
> LINUX_VERSION_MINOR:=$(shell echo $(LINUX_VERSION) | cut -d. -f2)
> LINUX_VERSION_TRIPLE:=$(shell echo $(LINUX_VERSION) | cut -d. -f1-3)
> (yeah, it could be better written and more standardized... but it works
> for now.) and in target/device/geni586/Makefile.in:
> ifeq ($(ARCH),i586)
> ac_cv_sizeof_char=1 \
> ac_cv_sizeof_unsigned_char=1 \
> ac_cv_sizeof_short=2 \
> ac_cv_sizeof_short_int=2 \
> ac_cv_sizeof_unsigned_short=2 \
> ac_cv_sizeof_unsigned_short_int=2 \
> ac_cv_sizeof_int=4 \
> ac_cv_sizeof_long=4 \
> ac_cv_sizeof_long_int=4 \
> ac_cv_sizeof_unsigned=4 \
> ac_cv_sizeof_unsigned_int=4 \
> ac_cv_sizeof_unsigned_long=4 \
> ac_cv_sizeof_unsigned_long_int=4 \
> ac_cv_sizeof_off_t=4 \
> ac_cv_sizeof_size_t=4 \
> ac_cv_sizeof_char_p=4 \
> ac_cv_sizeof_unsigned_char_p=4 \
> ac_cv_sizeof_voidp=4 \
> ac_cv_sizeof_long_long=8 \
> ac_cv_sizeof_long_long_int=8 \
> ac_cv_sizeof_unsigned_long_long=8 \
> ac_cv_sizeof_unsigned_long_long_int=8 \
> ac_cv_sizeof_off64_t=8 \
> Since there are a lot of broken "configure" scripts out there, and
> there's no point in having 50 or more packages try to figure out the
> native size of a "long", then why not predefine a lot of this?
Probably because noone thought about this.
> What am I missing?
> I'll try to go over my mods to the makefiles, and if I see anything
> useful, I'll post the diffs.
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> buildroot at uclibc.org
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