These lines tell MASM that the code makes reference to two externally-defined procedures. With cdecl, the calling function is responsible for removing arguments from the stack, whereas with stdcall it’s the called function’s responsibility to do stack cleanup before it returns. These two conventions only differ regarding stack cleanup. Is called by pushing arg3 onto the stack first, followed by arg2 and arg1: push arg3

So a function whose prototype looks like: MyFuction(arg1, arg2, arg3) stdcall and cdecl conventions are similar: both pass arguments on the stack, and the arguments are pushed in right to left order. You may also rarely see the _fastcall convention look it up for more details. These details are known as the calling convention.Īll of the Win32 API functions use the _stdcall convention, while C functions and the C library use the _cdecl (or just plain “C”) convention. If the arguments are passed on the stack, then the two functions must also agree on who’s responsible for popping them off afterwards, so the stack can be restored to its original state. The caller and callee must agree on where the arguments will be placed, and in what order, or else the code won’t work correctly. When one function calls another, it must somehow pass the arguments to the called function. Nothing is exported in this example, so the choice doesn’t really matter, but I’ll choose stdcall. The second parameter gives the default calling convention for procedures exported from this file, and can be either C or stdcall. The memory model for all Win32 programs is always flat. 586 here if you want to avoid generating any instructions not compatible with those older CPUs. Any Intel-based machine from the past 15-20 years will be able to run this, so it’s a good generic default. This tells the assembler to generate x86 code that’s compatible with the Intel 686 CPU or later, aka the Pentium Pro. > link /subsystem:windows /out:msgbox.exe kernel32.lib user32.lib msgbox.obj Save the example file as msgbox.asm, and use MASM to build it from the command line like this: > ml /coff /c /Cp msgbox.asm If you’ve got any version of Microsoft Visual Studio installed on your PC, including the free Visual Studio Express versions, then you’ve already got MASM: the Microsoft Macro Assembler. MsgText db 'Windows assembly language lives!', 0 Samuel A on Raspberry Pi GPIO Programming in C.chrisdaun on ROM Hacking Tutorial with ROM-inator II.John Payson on Oceania Has Always Been at War with Eastasia: Dangers of Generative AI and Knowledge Pollution.Milan on Explaining 4K 60Hz Video Through USB-C Hub.Mack on Floppy Emu Disk Emulator for Apple II, Macintosh, and Lisa.Yellowstone Universal Disk Controller for Apple II Floppy Emu Disk Emulator for vintage Apple II, Macintosh, and Lisa

Mac assembly language