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In our wrapper, we forcibly add the -march=, -mcpu= and-mtune= flags
to the actual compiler, this in an attempt to always generate correct
and optimised code for the target.
But in some cases, the caller knows better than we do, and passes its
own set, or subset of those flags. In this case, some may conflict with
the ones we pass. The most prominent offender being the Linux kernel.
For example, on the ARM Raspberry Pi, the Linux kernel will set the
-march=armv6 flag and no -mcpu= flag, but we pass -mcpu=arm1176jzf-s,
which conflicts:
drivers/scsi/scsi_trace.c:1:0: warning: switch -mcpu=arm1176jzf-s
conflicts with -march=armv6 switch
(and so for all the files the kernel compiles, pretty messy)
(note: arm1176jzf-s is not an armv6, it is an armv6zk. Yeah...)
To avoid this situation, we scan our commandline for any occurence of
the possibly conflicting flags. If none is found, then we add our owns.
If any is found, then we don't add any of our owns.
The idea behind this is that we trust the caller to know better than
we do what it is doing. Since the biggest, and sole so far, offender
is the Linux kernel, then this is a rather safe bet.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Peter Korsgaard <jacmet@uclibc.org>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
To build and use the buildroot stuff, do the following:
1) run 'make menuconfig'
2) select the packages you wish to compile
3) run 'make'
4) wait while it compiles
5) Use your shiny new root filesystem. Depending on which sort of
root filesystem you selected, you may want to loop mount it,
chroot into it, nfs mount it on your target device, burn it
to flash, or whatever is appropriate for your target system.
You do not need to be root to build or run buildroot. Have fun!
Offline build:
==============
In order to do an offline-build (not connected to the net), fetch all
selected source by issuing a
$ make source
before you disconnect.
If your build-host is never connected, then you have to copy buildroot
and your toplevel .config to a machine that has an internet-connection
and issue "make source" there, then copy the content of your dl/ dir to
the build-host.
Building out-of-tree:
=====================
Buildroot supports building out of tree with a syntax similar
to the Linux kernel. To use it, add O=<directory> to the
make command line, E.G.:
$ make O=/tmp/build
And all the output files (including .config) will be located under /tmp/build.
More finegrained configuration:
===============================
You can specify a config-file for uClibc:
$ make UCLIBC_CONFIG_FILE=/my/uClibc.config
And you can specify a config-file for busybox:
$ make BUSYBOX_CONFIG_FILE=/my/busybox.config
To use a non-standard host-compiler (if you do not have 'gcc'),
make sure that the compiler is in your PATH and that the library paths are
setup properly, if your compiler is built dynamically:
$ make HOSTCC=gcc-4.3.orig HOSTCXX=gcc-4.3-mine
Depending on your configuration, there are some targets you can use to
use menuconfig of certain packages. This includes:
$ make HOSTCC=gcc-4.3 linux-menuconfig
$ make HOSTCC=gcc-4.3 uclibc-menuconfig
$ make HOSTCC=gcc-4.3 busybox-menuconfig
Please feed suggestions, bug reports, insults, and bribes back to the
buildroot mailing list: buildroot@uclibc.org