[fpc-devel] Building cross-compiler for arm-linux on win32

[Nikolai Zhubr]

Hi all,

(Sorry for flooding so much, but I've done some more testing!)

In order to isolate any possible wierd windows-specific issues, I've 
redone everything on x86_64-linux as a host, with the same 3.0.4 version 
starting compiler, same fpcbuild-3.0.4.zip as a source for cross-build, 
same arm-linux target and same binutils 2.31.1 built from stock source 
tarball, and same CROSSOPT="-CpARMV6 -Cfsoft".

Result seems exactly the same:

1. Adding the abovementioned ASTARGET+=-mfpu=softvfp to 
rtl/linux/Makefile[.fpc] is necessary, otherwise build will just fail.

2. Lots of "ARM BLX instruction ..." warnings from ld.

3. The resulting elf binary does not run on target device, generating 
"Illegal instruction"

So there definitely must be a problem somewhere.
Either I'm doing something really-really stupid, or maybe fpc 3.0.4 is 
incompatible with at least binutils >= 2.28 for arm target?
I'm wondering what version of binutils was used to release fpc 3.0.4 for 
arm?


Thank you,

Regards,
Nikolai

16.12.2018 14:01, I wrote:
> Hi,
>
> 16.12.2018 13:51, I wrote:
> [...]
>> So inserting
>> ASTARGET+=-mfpu=softvfp
>> allowed full cross-build to succeed. I have yet to see if the generated
>> binaries are actually usable.
>
> Ok, now the resulting elf executable has this (supposedly correct) flag:
> private flags = 600: [APCS-32] [VFP float format] [software FP]
>
> And, helloworld still fails to run:
> Illegal instruction
>
> And, I still see tons of "ARM BLX instruction ..." warnings from ld of
> this kind:
>
> C:\FPC\3.0.4\bin\i386-Win32\arm-linux-ld.exe:
> arm\units\arm-linux\rautils.o: warning: ARM BLX instruction targets ARM
> function 'SYSTEM_$$_POS$CHAR$SHORTSTRING$$LONGINT'
> C:\FPC\3.0.4\bin\i386-Win32\arm-linux-ld.exe:
> arm\units\arm-linux\rautils.o: warning: ARM BLX instruction targets ARM
> function 'fpc_shortstr_copy'
> C:\FPC\3.0.4\bin\i386-Win32\arm-linux-ld.exe:
> arm\units\arm-linux\rautils.o: warning: ARM BLX instruction targets ARM
> function 'fpc_shortstr_to_shortstr'
> C:\FPC\3.0.4\bin\i386-Win32\arm-linux-ld.exe:
> arm\units\arm-linux\rautils.o: warning: ARM BLX instruction targets ARM
> function 'SYSTEM_$$_DELETE$OPENSTRING$LONGINT$LONGINT'
>
> Currently, my build command is:
> make OS_TARGET=linux CPU_TARGET=arm NOGDB=1 CROSSCOMPILE=1
> CROSSOPT="-CpARMV6 -Cfsoft" all
>
> Any hints?
>
>
> Thank you!
>
> Regards,
> Nikolai
>
>>
>>
>> Thank you!
>>
>> Regards,
>> Nikolai
>>
>>>
>>>
>>> Thank you!
>>>
>>> Regards,
>>> Nikolai
>>>
>>>> Thing is, object files compiled from pascal (like system.o) still get
>>>> this suspicious VFP flag even after I started using CROSSOPT="-CpARMV6
>>>> -Cfsoft". However, object files compiled from assembler sources (like
>>>> prt0.o) does not. I'm trying to find where it comes from.
>>>>
>>>> arm-linux-objdump.exe -p prt0.o
>>>> prt0.o: file format elf32-littlearm
>>>> private flags = 0: [APCS-32] [FPA float format]
>>>>
>>>> arm-linux-objdump.exe -p system.o
>>>> system.o: file format elf32-littlearm
>>>> private flags = 600: [APCS-32] [VFP float format] [software FP]
>>>>
>>>> As a side note, I suddenly realised that I don't need any specially
>>>> crafted version of binutils as long as I target linux and build
>>>> binutils
>>>> from source. Standard binutils source tar compiles with almost zero
>>>> effort on modern mingw, at least for linux target.
>>>>
>>>>
>>>> Thank you!
>>>>
>>>> Regards,
>>>> Nikolai
>>>>
>>>>
>>>> 15.12.2018 23:23, I wrote:
>>>>> Still can not understand this ".o uses VFP instructions, whereas .\pp
>>>>> does not", but because I build binutils myself I've found and disabled
>>>>> the ld error exit on (in_flags & EF_ARM_VFP_FLOAT) != (out_flags &
>>>>> EF_ARM_VFP_FLOAT), and then with such "fixed" binutils crossfpc build
>>>>> completed somehow. I can now produce arm-linux executables, but
>>>>> probably
>>>>> something is wrong anyway because this "VFP float format" is
>>>>> present in
>>>>> .o files but not in final elf executables:
>>>>>
>>>>> arm-linux-objdump.exe -p t.o
>>>>> t.o: file format elf32-littlearm
>>>>> private flags = 400: [APCS-32] [VFP float format]
>>>>>
>>>>> arm-linux-objdump.exe -p t
>>>>> t: file format elf32-littlearm
>>>>> Program Header:
>>>>> ......
>>>>> private flags = 0: [APCS-32] [FPA float format]
>>>>>
>>>>> (t.pas is a helloworld one-liner.)
>>>>>
>>>>> Besides, I get tons of warning from ld like this:
>>>>> C:\FPC\3.0.4\bin\i386-Win32\arm-linux-ld.exe:
>>>>> C:\FPC\3.0.4\units\arm-linux\rtl\system.o: Warning: Arm BLX
>>>>> instruction
>>>>> targets Arm function 'SYSTEM_$$_SYSINITSTDIO'.
>>>>>
>>>>> It looks like literally every function in every unit produce such a
>>>>> "Arm
>>>>> BLX instruction" warning. Seems suspicious.
>>>>>
>>>>> And finally, on the target board, the executable totally fails with:
>>>>>
>>>>> "Illegal instruction"
>>>>>
>>>>> Any hints?
>>>>>
>>>>>
>>>>> Thank you!
>>>>>
>>>>> Regards,
>>>>> Nikolai
>>>>>
>>>>>> It successfully produced object files, but ld refsuses to link them.
>>>>>> Again, the message is:
>>>>>> pp.o uses VFP instructions, whereas .\pp does not
>>>>>> (lots of these repeated)
>>>>>>
>>>>>> I'm guessing is that either some option is missing for ld to actually
>>>>>> accept that VFP is present, or rather I need to rebuild my binutils
>>>>>> for
>>>>>> a different (hard fp) target?
>>>>>>
>>>>>> (The exact call that fails now is arm-linux-ld.exe -s -L. -o .\pp
>>>>>> .\link.res)
>>>>>>
>>>>>>
>>>>>> Thank you!
>>>>>>
>>>>>> Regards,
>>>>>> Nikolai
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>> http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
>>>>>>
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>>>>>
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>>>>
>>>
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