Author Topic: Need some help with STRUC/ENDSTRUC  (Read 5093 times)

Offline dapleal

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Need some help with STRUC/ENDSTRUC
« on: July 01, 2012, 12:12:09 AM »
Hi. I´ve been trying Nasm 2.10 and Nasmx-1.0 for win32 OOP, and it´s been quite an interesting learning experience. I'm having some trouble with STRUC/ENDSTRUC and ISTRUC/IEND in Nasm 2.1. (I´m using ALINK). Say, If I declare two STRUC/ENDSTRUC definitions [struc A/endstruc, struc B/endstruc ], the compiler displays an error msg pointing to the first ENDSTRUC. The same happens with the ISTRUC/IEND at [segment .data]. It seems to me that the compiler does not allow more than one ENDSTRUC or IEND within the code. Is that right ? Cause Nasm documentation is not clear enough on that subject, and if I delete the error lines, it doesn´t work either. Any ideas ? Could it be a linker problem ?

Offline Keith Kanios

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Re: Need some help with STRUC/ENDSTRUC
« Reply #1 on: July 01, 2012, 12:29:10 AM »
The following is a simple (but not meant to be directly executed) example that successfully assembles to coff/win32.

Code: [Select]
[BITS 32]

struc A
.test RESD 1
endstruc

struc B
.test RESD 1
endstruc

[section .text]
lea ebx,[iA]
mov eax,DWORD[ebx+A.test]

[section .data]
iA:
istruc A
at A.test, DD 1
iend

iB:
istruc B
at B.test, DD 1
iend

If you get any errors with the above example, it is entirely ALINK.

Offline dapleal

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Re: Need some help with STRUC/ENDSTRUC
« Reply #2 on: July 01, 2012, 01:11:01 AM »
OK. It works. I've just had to type an entry point (..start:) underneth the [section .text] line.
I'm compiling like this: (as usuall, but not used STRUC/ENDSTRUC till now)

      nasm -f obj (name).asm
      alink (name).obj -o PE -subsys windows

It generates the .exe file, but still displays the following error msg:

     "Relocs 0:Warning 32 bit offset in 16 bit field"

That´s what´s been killing me all day.
Any suggestion of another free linker just for testing ?
Thanks for the help.


Offline Arq

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Re: Need some help with STRUC/ENDSTRUC
« Reply #3 on: July 01, 2012, 01:31:02 AM »
You can give a chance to Jeremy Gordon's neat linker GoLink (http://www.godevtool.com/) and say goodbye to imports libs mess also you can try out Polink from PellesC or the classic Microsoft link.exe.

Regards.

Offline Keith Kanios

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Re: Need some help with STRUC/ENDSTRUC
« Reply #4 on: July 01, 2012, 05:11:26 AM »
+1 for GoLink. It is/was bundled with NASMX. IIRC, NASM32/NASMX started with ALINK, then moved to PoLink due to shortcomings with ALINK, and finally to GoLink for further quality/feature considerations.

Offline Frank Kotler

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Re: Need some help with STRUC/ENDSTRUC
« Reply #5 on: July 01, 2012, 06:52:15 AM »
Quote
It generates the .exe file, but still displays the following error msg:

     "Relocs 0:Warning 32 bit offset in 16 bit field"

"-f obj" is by default a 16-bit format. As you know(?), it is necessary to declare each section/segment "use32". It might not hurt to put "bits 32" at the top of the file, just to "catch" anything that's not in a segment. Although "-f obj" and Alink may be considered "obsolete", it "should" still work fine and I'm not aware of any disadvantage.

Best,
Frank


Offline dapleal

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Re: Need some help with STRUC/ENDSTRUC
« Reply #6 on: September 30, 2012, 02:15:48 AM »
Hi. Just to tell I realized what I was doing wrong with “ISTRUC/IEND”.  Sorry for the trouble, it works just like you said.

On page 70 of the NASMDOC.PDF file (NASM 2.10 documentation)  there are two given examples on “STRUCTURE / ENDSTRUC”. While on the following page there´s only one given on “ISTRUC / IEND”.

I would dare to suggest you guys may also include the corresponding “ISTRUC/IEND” example to the other one.  It may save hours of frustration to other beginners like me. That is:

struc mytype
 .long: resd 1
 .word: resw 1
 .byte: resb 1
 .str:  resb 32
endstruc      ; (page 70)

mystruc:
istruc mytype
 at mytype.long, dd 123456
 at mytype.word, dw 1024
 at mytype.byte, db ’x’
 at mytype.str,  db ’hello, world’, 13, 10, 0
iend
(there is no such example on page 71 within the .pdf doc file)

What I was doing wrong was:
mystruc:
istruc mytype
 at .long, dd 123456
 at .word, dw 1024
 at .byte, db ’x’
 at .str,  db ’hello, world’, 13, 10, 0
iend

Thanks for the help. Congratulations for the great job with NASM and NASMX.