Many BSPs Fail to link CXX tests
sebastian.huber at embedded-brains.de
Tue Jan 5 10:35:17 UTC 2016
On 04/01/16 03:47, Joel Sherrill wrote:
> On Sun, Jan 3, 2016 at 8:26 PM, Chris Johns <chrisj at rtems.org
> <mailto:chrisj at rtems.org>> wrote:
> On 01/04/16 12:55, Joel Sherrill wrote:
> On SPARC/SIS, the main lesson I learned is that if the executable
> dropped to something ridiculously small, then something was
> broken. I
> had one iteration where hello.exe had 48 bytes of code. :)
> Nice work.
> That much was pretty obvious. Why was a problem. :)
> Any thoughts on how to catch breakages on BSPs we can only link?
> Can you get a suitable list of functions that must be present in
> the executable and check they are present with nm?
> It should be simple if the breakage is between the entry point and the
> rest of the BSP. If hello does not include bsp_start() or
> rtems_initialize_data_structures(), then it is known to be broken.
> This is what broke on sis -- the first 16 instructions of the start
> code had no dependency on anything else. So the linkages were
> satisfied and nothing else pulled in. :)
> I think this is a good thing to try to sweep in for 4.12 since
> we can
> easily check 4.11 vs 4.12 for breakages on specific BSPs.
> So this is a once only check and not something we always check for?
> Should be one time only. If the linkage between the start code and C
> code is correct, it will stay correct. Once you get to C code,
> everything should be magically correct.
> I think this is simple enough in principle where it could be written
> up as a series of GCI tasks. One task per BSP given the amount of
> time. It isn't much editing but I would want
> (1) patch to make/custom/XXX.cfg
> (2) the commit message to include:
> + base size for some tests like hello and ticker (same on all BSPs)
> + new size for the same tests
> (3) Confirmation with hello.num posted to GCI task so we can see the
> symbols ourselves. But they should have checked it.
> OTOH, one of us could probably sweep the argument changes into the
> custom files quickly, my build scripts capture the size of the tests
> already, and we are used to scripting and automated passes. Maybe I
> should play the next couple of weeks. If someone wants to help, it
> would be nice to have some.
I am in favour to enable this for all BSPs. Basically the linker scripts
must have the KEEP () directive for the relevant sections. So, for a
symbol test we should pick up one using the network stack and one using
a global C++ constructor.
Do we really have to patch all the XXX.cfg files? Maybe wait until we
have a new build system and add this to a common place?
Sebastian Huber, embedded brains GmbH
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