[fasmg] Problem creating a MS COFF

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alorent

Joined: 05 Dec 2005
Posts: 221

alorent 30 Nov 2022, 05:55

Hi,

I'm moving from FASM to FASMG but I have a problem creating a COFF .obj file.

I'm still learning about all the possible "include" files to include in fasmg, but I'm a bit confused yet.

This is my code to create a simple "MS COFF" OBJ:

Code:

include 'format/format.inc'

format MS COFF

include 'win32ax.inc'

public MyFunction as '_Myfunction@4'

.code 

MyFunction proc param1
    
    mov eax, [param1]
    ret 

MyFunction endp

But I get the following error:

Code:

macro format?.MS? [3]:
        COFF.Settings.Characteristics = IMAGE_FILE_32BIT_MACHINE or IMAGE_FILE_LINE_NUMS_STRIPPED or IMAGE_FILE_BYTES_REVERSED_LO
Processed: COFF.Settings.Characteristics = IMAGE_FILE_32BIT_MACHINE or IMAGE_FILE_LINE_NUMS_STRIPPED or IMAGE_FILE_BYTES_REVERSED_LO

Error: symbol 'IMAGE_FILE_32BIT_MACHINE' is undefined or out of scope.

I have played a lot with it, but no luck yet. I guess that I'm putting "format" and include lines in the wrong order or duplicated?

Thanks!

30 Nov 2022, 05:55

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8359
Location: Kraków, Poland

Tomasz Grysztar 30 Nov 2022, 07:00

WIN32AX.INC was designed to work with PE output, and I forgot to consider that it may have worked with other formats. Both fasm's and fasmg's version automatically set up PE format unless it was already selected, but they do so in different ways, hence incompatibility.

The version for fasm was doing this:

Code:

virtual at 0
 xchg eax,eax
 detected_16bit = $-1
end virtual

if detected_16bit
 format PE GUI 4.0
end if

Detecting a default "use16" setting and in such case setting up default PE output. This worked with COFF as well, because selecting COFF was also switching to "use32" code.

In case of fasmg this logic would not work, because there might not be instruction set at all in the beginning, so it might not be possible to determine the mode in such way. That's why fasmg's version simply checks whether PE format has been set up already:

Code:

if ~ definite PE
        format PE GUI 4.0
end if

I should go back to this and consider some changes, perhaps it could also check for presence of x86 instruction set:

Code:

if ~ definite PE & ~ definite x86.mode
        format PE GUI 4.0
end if

30 Nov 2022, 07:00

alorent

Joined: 05 Dec 2005
Posts: 221

alorent 30 Nov 2022, 08:14

Thanks Tomasz!

You are right, that line causes the problem.

I have removed that code from WIN32AX.INC and not it assembles correctly.

Thanks again

30 Nov 2022, 08:14

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