YASM error: 'coff: invalid relocation size'

[HJED]

Hello i have this annoying error in my code
start.asm(443) : error: coff: invalid relocation size
this error only occurs when I assemble the code using the win64 format
but this is required as i am using a windows 64bit Linker

the code in question is

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extern _portid
extern _res
global _aoutportb
 _aoutportb:
   mov dx, _portid
   in ax, dx
   mov [_res], al

_res is declared in my c++ code as

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unsigned char res=0;

and _portid is declared as

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unsigned short portid

(the value varies)

line 443 is in the above asm code

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 mov dx, _portid 

thanks for any help

[jnc100]

Perhaps the 64-bit version of coff does not support 16 bit relocations? My guess is its trying to output something like 66 ba 00 00 (i.e. mov dx, imm16) and then point the relocation to the 16-bit field (because what you're actually asking for is an address). If you want the actual value of the portid variable, try mov dx, [_portid], which should produce an opcode using modrm and a 32-bit offset (and therefore should assemble fine).

Regards,
John.

[HJED]

thank you for your help!