RFC: PowerPC bsp_specs Clean Up Question

[Joel Sherrill]

On Dec 21, 2017 3:03 PM, "Chris Johns" <chrisj at rtems.org> wrote:

On 22/12/2017 02:01, Joel Sherrill wrote:
> I'm not opposed to this but it requires even more delicate editing that I
can't
> easily test.

If something breaks and it is reported we can look at fixing it. If
something
breaks and it is not reported is it broken? ;)


Like a tree falling in the woods. :)


> We can get rid of bsp_specs and do this largely at the same time. The
> specifications in GCC will have to be tinkered with to address what's
left in
> bsp_specs so the specs can do this.

I think GCC's default configuration should be user focused and not BSP or
internally RTEMS focused. I see this meaning GCC's model is the same for all
BSPs and the options to access a BSP are similar.


Agreed. I may be deeper in this mess and seeing things that aren't obvious
at first glance. The crti/n, begin/end vary a bit per target architecture
and (I think) the best we can do is go back to GCC default behavior as a
baseline. Sebastian and you were hinting at that in an earlier message.

Switching between crt0.o and start.o is magic after that.

FWIW I only see three linkcmds where STARTUP is not start.o. so that isn't
hard to fix.

The entry symbol is usually a variant of start with 0 to 2 underscores. A
handful have different symbols or appeared to start in the version.

I can push what I have done and continue to nibble.


> But I haven't figured out precisely what to do with gcc at this point.

The difficult part is locating start.o and similar object files. RTEMS
currently
implements a horrible hack using -B. This option not only locates a
bsp_specs
file it also adds a search path for locating .o and other files. I have only
just uncovered this as part of removing preinstall and it is a horrible
problem
to solve. For example what happens if I create start.o in my application and
provide it on the command line to the linker with a -B to the location
RTEMS's
start.o is located? Does GCC know what I want, is this option order
dependent or
something else? A simple solution here is use RTEMS specific names but the
idea
of needing -B seems wrong.


-B is a standard option which specifies DIR is a system directory. Implies
a -L and -I.

If it has magic beyond that, I don't see it.

Users providing their own start.o outside a BSP isn't a use case I want to
worry about. If there is another reason to avoid -B, ok.

Also the -specs option is the one that bothers me the most. It implies
reading a very GCC specific file.


Chris
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