Linker problems with arm-wince, need help/info

[Pedro Alves]

Chad J wrote:

> pedro alves wrote:
>
>> That's what I meant :) An extern (C) main in phobos that does all the 
>> setup and then calls a _Dmain. I even guessed the name right :)
>>
>> $ grep main 1nm.txt 00000024 R __D3gcc6config21dirent_remaining_sizek
>> 00000a38 T __D3std4math9remainderFeeZe
>>         U _remainder
>> dgccmain2.o:
>> 00000094 T __d_run_main
>> 00000000 t __d_run_main2goFZv
>> rundmain.o:
>>         U __Dmain            <------- probably the D main in app code.
>> 00000000 T __d_run_Dmain
>>         U __d_run_main
>> cmain.o:
>>         U __Dmain
>>         U ___gccmain
>>         U __d_run_main
>> 00000000 T _main           <------- look here, it is underscored :)
>>
>> So main is being underscored. Take a look at where that _main (should 
>> be main in source form) is defined. I would guess,
>> that it is implemented in D with extern (C). I think the D frontend 
>> will need to be extended to support -fno-leading-underscore, at least 
>> for
>> extern (C) function calls/declarations, but I guess supporting it for 
>> *all* function decls/calls will be easier, probably there will be a 
>> single function that
>> handles the mangling. Look for that.
>
> I tried looking through the frontend.  There was a file dedicated to 
> mangling (gcc/d/dmd/mangle.c).  I still can't figure out where the 
> underscoring is handled, at least for C linkage.  I tried one obvious 
> looking line change, but it didn't fix the C linkage at all.  I feel 
> kinda helpless in the frontend, as I do not know much about compiler 
> internals, much less GCC internals.  Maybe David can help here? Please?
>
Try putting a breakpoint there and stepping until the underscore is 
prepended. I don't know much about these parts of gcc either.

> I also don't understand why this would have any effect on D linkage 
> like _D3std4file5writeFAaAvZv, at least that seems to be D linkage 
> since it has the module name and the trailing type info.  

Well, to the linker, it is just a symbol like all the others. The 
mangling is there to make the function name unique, so you can have 
overloading at the D level, but to the linker, it has
no difference to any other C function or ASM function. The thing is, the 
mangler converts (i'm guessing the name now) std.file.write(...) into 
_D3std4file5writeFAaAvZv, but somewhere
between that and the emitting to the .s file that gets passed to the 
assembler, an underscore is prepended to the symbol, turning it into 
__D3std4file5writeFAaAvZv.
Find the place where this underscore is added, and disabled it. That's 
the place the -fno-leading-underscore should be respected. You can also 
grep the gcc sources to see
where that switch is handled for c and c++, and do the same.

> With respect to underscoring, does the linker handle symbols any 
> differently than say, an x86 linker?

With respect to underscoring, yes, it accounts for the underscore when 
the target is underscored, and doesn't, when the target isn't. You can 
look at binutils/ld/pe-dll.c to see it in action.
I have some hacks in cegcc's version of binutils that are needed here. 
Grep for "pedro" there if you are curious :)

...

I looked at the attatchment you sent. Well, you definitily have an 
underscoring mismatch.

Another thing. If after you fix this underscoring business you stil get 
errors like:
/root/gcc/gdc-4.0.3/libphobos/std/typeinfo/ti_creal.d:31: variable 
'___gtdf2' can't be auto-imported. Please read the documentation for 
ld's --enable-auto-import for details.

You will need to use the --enable-runtime-pseudo-reloc linker switch, 
but that needs runtime support, that mamaich's toolchain doesn't have. 
Luckily, cegcc has it :)

Cheers,
Pedro Alves