Starting a new thread since this is off-topic for "MSP430 simulator in gdb".
The discussion is how to take advantage of newlib's libc
infrastructure while replacing the system interface that is by default
provided by libgloss: i.e. implementations of
read()/write()/sbrk()/gettimeofday() and other functions that
interface with a host environment (hardware, OS framework, simulator,
whatever).
The msp430-elf port appears to make this difficult in two ways:
1) gcc has a hard-coded LIB_SPEC that automatically adds -lnosys
whenever the user fails to specify the simulator as the target. The
need in the situation being discussed is to provide an alternative
implementation to -lnosys. I've worked around this by removing
%{!msim:-lnosys} from LIB_SPEC and building a new toolchain.
2) The msp430 port of newlib is nearly unique in discarding the
libnosys implementation provided by newlib in favor of its own
crippled implementation. (Of the dozen+ supported newlib targets
spu-* is the only other one that does this). I've worked around this
by patching the msp430 target to remove the CIO-based -lnosys provided
libgloss/msp430/Makefile.in and instead keep the default
config_libnosys=true, leveraging the standard libgloss stub system
function implementation.
I've verified that with this toolchain I can use the newlib standard
option -specs=nosys.specs to link applications with the stubbed
version from libgloss for cases where I don't want to replace the
implementation. I've also done enough testing to be convinced I can
provide an alternative implementation of the system interface
functions, as is normally permitted by newlib.
However, the changes necessary to make this work require building a
special version of the toolchain with modified upstream sources.
Works for me; not really acceptable to most users. So presumably this
isn't the way I'm supposed to do this.
How am I supposed to do this?
Peter
On Thu, Jun 5, 2014 at 6:09 AM, Peter Bigot <big...@acm.org> wrote:
> On Tue, Jun 3, 2014 at 6:35 PM, DJ Delorie <d...@redhat.com> wrote:
>>
>>> You can do that with the RH newlib as long as you don't link in
>>> libgloss's versions of the low-level routines - i.e. remove -lgloss
>>> from your link line and add -lbspacm.
>>
>> To clarify: don't link in -lnosys if you're not compiling with "-msim"
>> or don't link in -lsim if you are compiling with "-msim"
>>
>> Both of these are linked at the same point as libc and libgcc, by the
>> gcc driver, depending on whether or not you use the -msim option.
>
> Yes, first impressions suggest if I could get rid of libgloss entirely
> I could do what I want.
>
> But since gcc's LIB_SPEC helpfully adds -lnosys for me at no extra
> charge when I don't use -msim, how can I avoid linking it in?
>
> Peter
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