[Buildroot] Q: Modifying package builds?

[Buildroot] Q: Modifying package builds?

[Michael.Forkey at elektrobit.com]

As of about a month ago I was completely new to Linux & Linux
development, buildroot and development for embedded devices. So there
are a lot of holes in my buildroot knowledge. If there is a FAQ
somewhere please point me to it. I haven't found one (at least not one
for these questions.)

I work on a project which uses buildroot targeting the ARM9 processor. I
run buildroot on both an Ubuntu VM and on a server running Red Hat
Enterprise 5. This matters because the results are different between the
2 (very frustrating) which is part of the need to ask this (these)
questions.

I have to use an older version of buildroot which matches my customer's.
It is old enough that there are significant differences between it and
the current version for the packages I am building (libgtk2-directfb)
and that has made back-porting of some necessary patches a pain. 

I need to be able to predictably modify the package build. I need to
apply fixes to various files (.mk and Makefile[.am|.in]) and have them
picked up. Currently the only way I know to reliably get the
configuration for a package to run is to run "make distclean". Then I
re-run "make" iteratively until I hit all the breaks and re-apply all my
fixes.

Some of the fixes I've needed to make are to correct include paths which
are not correct. For example, I have had failures because the path to a
header file is .../lib/<package> in the Makefile but it is actually in
.../lib/usr/<package>. I have also seen the reverse as well (i.e. path
is under .../lib/usr when it is really under .../lib.)

Another need is to change compiler options - turn off optimizations
(i.e. -O0 instead of -O2 or -Os), or add -DDEBUG, etc.

**My primary question(s) for this group is**: How can I change the
configuration of packages before they are built? 

There are a couple ancillary questions which go along with this. 

1. Can I create a patch (for my local use only) and apply it somehow
after a package is unpacked but before it is built?
I don't know how to use the patch mechanism yet, but I will learn it if
it helps (recommendations on useful ways to do that appreciated.) 

2a. What are the points I can interrupt and restart the process without
screwing it up? 2b. Or how do I make changes and then restart the build
so they get properly picked up?
I have tried deleting the .configured file in a package's build_arm
directory after I have made changes to the package's Makefile or
Makefile.am (or .in, I can't remember.) But that doesn't seem to
entirely work right. Some things don't get re-gen'd.

3. Is there anyway to tell the build to continue on errors? 
I realize some of the failures will cascade into other packages. But I
want it to unpack everything so I can make all the changes I need to
once. (I have cataloged all the pieces I need to change in the entire
build.)

4. As a variant on that question: is there some way to get all the
packages unpacked before building, i.e. similar to running "make source"
to get all the packages downloaded? Can I get them downloaded and
unpacked, too?

Any help is appreciated.

Thanks,
mf


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[Buildroot] Q: Modifying package builds?

[Ulf Samuelsson]

> **My primary question(s) for this group is**: How can I change the
> configuration of packages before they are built? 

The build of a package <package> is goverened by
<buildroot>/packages/<package>/<package>.mk

Ensure that this file contains the target:

<package>-unpacked:    <package>-source

The target should be completed when the package has been decompressed
in "build_arm/<package>" and any patched present in 
"<buildroot>/packages/<package>/" has been applied.

Unpack and apply the existing patches with:

$ make <package>-unpacked
$ cd build_arm
$ mv <package> <package>-0rig
$ cd ..
$ make <package>-unpacked

Now you have both 
"build_arm/<package>" and "build_arm/<package>-0rig"

Make any modifications to "build_arm/<package>" and create a patch

$ cd build_arm
$ diff -urN <package>-0rig <package>    >    <package>-###.patch
$ mv <package>-###.patch ../packages/<package>

"###" should ensure that the new patch is applied after all existing patches.

This will handle one package at a time.

It might be a good idea to have a generic target which unpacks and patches
all packages but I am not aware that this exist and can't check right now.
Most of the packages support "make source", but very few support
"make unpacked".



Best Regards
Ulf Samuelsson