configure options translated to waf config.ini?

[Chris Johns]

On 25/9/20 2:48 am, Joel Sherrill wrote:
> I can't find any documentation which guides translating a 
> RTEMS configure command into the appropriate set of
> options in a config.ini file for waf. The only example I could
> find has BUILD_TESTS which implies it builds all tests 
> rather than just samples.
> 
> Guidance on translating configure options to config.ini
> statements would be appreciated by me and I am sure
> by others who will have to update their build procedures.
> 
> Guidance on the variables used to override configure.ac <http://configure.ac>
> values is also needed but that isn't quite as critical as 
> just translating the various enable/disable settings.
> 

I have not done this yet so I do not have a 1:1 translation for configure
options. Having this documented would be good.

I discussed with Sebastian earlier in the week how this is to work and this is
what I learnt ...

1. The `--rtems-bsps` option only seems to effect the `bsp_defaults` target. The
configure process uses the .ini file you provide via the `--rtems-config`
option. The default is `config.ini` if that option is not supplied.

2. The .ini file is only referenced by the configure phase of waf. It defines
all the BSPs to built and any overriding option. You normally only have options
in a .ini that are _not_ defaults. If you enter:

./waf bsp_defaults > config.ini

all BSPs will be built and with default options. This is not what you normally want.

3. You can have a `[DEFAULTS]` (all caps) section and any option in that section
applies to all BSP that support it. For example:

[DEFAULTS]
BUILD_TESTS = True

will build the testsuite for all defined BSPs.

4. To build a BSP using its defaults simply add the BSP name as a section
header. Note, BSP names use the RTEMS standard `arch/bsp` format. For example:

[DEFAULT]
BUILD_TESTS = True

[arm/beagleboneblack]

[arm/xilinx_zynq_a9_qemu]

[i386/pc686]

[sparc/erc32]

Will build 4 BSPs with tests.

5. To change a default option you first need to see what is supported for your
BSP. Currently the only option available is with ./waf and the `bsp_defaults`
target with the BSP name of interest. For example:

$ ./waf bsp_defaults --rtems-bsp=sparc/erc32

Examine the list and add the one you want to change to your .ini file. For
example to change the optimisation level:

[sparc/erc32]
OPTIMIZATION_FLAGS = -O -g -fdata-sections -ffunction-sections

Remember to run the waf configure command again so the build picks up the
changed option. In the case waf will see the compiler command has changed and it
will rebuild all effected object files.

6. The .ini can be located any where. It does not need to reside in the source
tree. The `--rtems-config` option can be used to point to any you have located
outside the source tree. You can keep them in a separate repo or tool you
maintain to build RTEMS.

Chris