From: "Tom Hunt" <thunt1 AT falcon DOT lhup DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Using MASM generated COFF files with GPP (solution)
Date: Mon, 16 Apr 2001 16:45:01 -0400
Organization: East Stroudsburg University, Pennsylvania
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

I posted a question about this a while back and just found a solution to the
problem.  If someone posts a similar question in the future, this will fix
it.

say we're writing a function foo and assembling it with MASM using the
command line
ml /c /coff foo.asm

MASM will generate an object file instead of an exe file in COFF format
instead of its usual OMF format.

The foo.asm file should look something like this:

.386P              ; use protected mode 386 instead of real mode 386
.model flat       ; flat memory model for protected mode
public _foo      ; tells the assembler and linker that another module needs
this function
.code
_foo proc
    push    ebp
    mov    ebp, esp
    ...                        ; guts of the function goes here
    mov    eax, [return_value]     ; the return value should go into al, ax,
                                                ; or eax depending on the
                                                ; size of the return value
    mov    esp, ebp
    pop    ebp
    ret                ; do not put a number after ret to fix stack, the C++
program will take care of it
_foo endp

end            ; no main function in the assembly module

The C++ file that uses foo needs to declare foo as an extern like:

extern "C" int foo(...);    // declare the parameters and return value here

that's all there is too it.  When I compiled the whole thing, the link phase
took a lot longer than it usually does, so just minimize the dos window
you're using if you're running Windows and do something else for a bit.

Tom