building a basic win32 exe

[hipppofear]

I am trying to build a basic win32 exe using masm.  I only need the essentials (just want it to be able to compile and run).  My code is below.  I also get the following error when trying to compile it "ml test.am":

/z2
"test.obj"
"test.exe"
NUL
LINK : warning LNK4044: unrecognized option "z2"; ignored
test.obj : warning LNK4033: converting object format from OMF to COFF
LINK : fatal error LNK1181: cannot open input file "test.exe"

Code Select Expand


.386
.model flat

.CODE

start:

xor eax, eax

END


What am I doing wrong?  Thanks

[Tedd]

Code Select Expand

.386
.model flat, stdcall

.code
start:
    xor eax,eax
end start


"end start" is required to indicate the end of the section (don't ask me why :P)
I tried to remove the calling convention "stdcall" but that caused complaints :wink



A minimal (useful?) program looks like this (in fact, this is what I usually use a starting template :bg)

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.386
.model flat, stdcall
option casemap:none
include windows.inc
include kernel32.inc
includelib kernel32.lib

.code
start:
    invoke ExitProcess, NULL
end start

[joe]

Hi hippofear!
To successfully compile it, are needed at least 2 changes (this says Tedd too):
.386
.model flat,stdcall   ;not only stdcall
.CODE
start:
xor eax, eax
end start   ;not only end

Inlude are needed, if You want to use some system API's. ExitProcess is used to correctly end Your exe.

[AeroASM]

YOu need to use:

ml /c /coff test.asm
link /subsystem:windows test.obj

to compile.

You also need a ret or an invoke ExitProcess,0 after the xor eax,eax

[hipppofear]

thanks a lot guys. 

AeroASM: can you tell me why i had to use the commands you posted to compile above^ instead of only "ml test.asm"?

[Bieb]

Just ml file.asm would produce a raw object file.  You need to make sure you assemble the right type of object file and then feed it to the linker to make an executable.

[PBrennick]

hipppofear,
All these answers are excellent.  If I were you, I would save Tedd's template code and use it  as the start of every program you make.  Also, save Aero's code as a batch file called makeit.bat.  As time goes on you will add more to it but it is a working beginning for you.

hipppofear is an interesting handle.

Paul

[Jeff]

if you want the ABSOLUTE basic:

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.386
.MODEL FLAT

INCLUDELIB Kernel32.lib
ExitProcess PROTO STDCALL,:DWORD

.CODE
_Start:
    INVOKE ExitProcess, 0
END _Start

[hipppofear]

thanks again.

I have an off the topic questions, the instruction below gives me the following error:

Assembling: test.asm
test.asm(28) : error A2070: invalid instruction operands

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    cmp [esi+eax], 0

I want to compare the value located at esi+eax and 0.  this worked in other compilers but im not sure why it doesnt with masm.  I tried "cmp dword [esi+eax], 0" but it didnt work.

[GregL]

hipppofear,

MASM needs to know what size and type of memory variable to compare to zero.

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cmp dword ptr [esi+eax], 0


You were close with 'dword', in MASM it has to be 'dword ptr'.

[Mark Jones]

Be sure to skim over the ASMINTRO.HLP file in \masm32\help - this will answer a lot of questions. :bg

[AeroASM]

Just ml file.asm would produce a raw object file.  You need to make sure you assemble the right type of object file and then feed it to the linker to make an executable.

You mean ml /c file.asm

WIthout the /c it tries to link it as well.

[hutch--]

hipppofear,

You get these odd problems because most people use the shorthand notation in MASM where you only specify the data size if ther operands do not. When you write an instruction like the following,

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cmp [esi+eax], 0


You have a memory operand and an immediate value and neither tell the assembler the size required so the shorthand form does not work. You can successfully write MASM with fully specified sizes with code like,

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mov DWORD PTR [eax], edi
or
cmp DWORD PTR [esi+eax], 0


and it works fine but where the asembler can work out the size from the operands, it does not have to be done.

[PBrennick]

Which means to say, if you prefer the shorthand notation method, you can do it this way:

xor ebx, ebx
cmp [eax+esi], ebx

or you can declare a variable as dword and use that:

anything  DWORD 0
cmp [eax+esi], anything

Using either method, you can use any value that fits into the size of a DWORD, not just zero.

either way works but the second method is preferable as it does not tie up an extra register

Paul

[hutch--]

You actually need an OFFSET with the .data section operand.

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    .data
      anything  DWORD 0
    .code
    cmp [eax+esi], OFFSET anything


Here is te disassembly of the three.

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00401023 813C0618304000         cmp     dword ptr [esi+eax],403018h
0040102A 33C0                   xor     eax,eax
0040102C 390406                 cmp     [esi+eax],eax
0040102F 833C0600               cmp     dword ptr [esi+eax],0


Doing a direct compare to an immediate zero is the smallest because of how the opcodes work for an immediate that is within BYTE range, te XOR version is next and the compare to a value in the .DATA section is the largest.