How to build a x64/x86-project with a standalone x64/x86 assembly file
1) Start Visual Studio (Community) 2017 and choose FILE - New - Project.
2) In the next window choose Empty Project.
3) Make sure, that the project is highlighted in the Solution Explorer and and choose PROJECT - Build Customizations....
4) In the next window tick masm(.targets,.props) and click on OK.
5) Choose PROJECT - Add New Item from the menu.
6) In the next window choose C++File(.cpp) and – IMPORTANT! – give it a name with an .asm extension. Click on Add.
7) Now you can fill the file with content.
Source.asm:
EXTERN GetStdHandle : PROC
EXTERN WriteFile : PROC
EXTERN ExitProcess : PROC
.DATA?
hFile QWORD ?
BytesWritten DWORD ?
.DATA
hello BYTE 'Hello world!', 13, 10
.CODE
main PROC
; https://blogs.msdn.microsoft.com/oldnewthing/20160623-00/?p=93735
sub rsp, 40 ; Shadow space (4 * 8) & 1 parameter (8 bytes)
; https://docs.microsoft.com/en-us/cpp/build/stack-allocation
and spl, -16 ; Align to 16
; https://msdn.microsoft.com/library/windows/desktop/ms683231.aspx
mov ecx, -11 ; DWORD nStdHandle = STD_OUTPUT_HANDLE
call GetStdHandle ; Call WinApi
mov hFile, rax ; Save returned handle
; https://msdn.microsoft.com/library/windows/desktop/aa365747.aspx
mov rcx, hFile ; HANDLE hFile (here: Stdout)
lea rdx, hello ; LPCVOID lpBuffer
lea r9, BytesWritten ; LPDWORD lpNumberOfBytesWritten
mov r8d, LENGTHOF hello ; DWORD nNumberOfBytesToWrite
mov qword ptr [rsp+32], 0 ; LPOVERLAPPED lpOverlapped = NULL
call WriteFile ; Call WinAPI
exit:
; https://msdn.microsoft.com/library/windows/desktop/ms682658.aspx
xor ecx, ecx ; Set RCX to null for return value
call ExitProcess ; Call WinAPI to exit
main ENDP
end
This is a 64-bit Console application that starts at the procedure main.
8) Change the Solution Platforms to x64
9) Choose PROJECT - Properties.
10) In the Properties window you have to complete two linker options:
- Entry Point: main
- SubSystem: Console (/SUBSYSTEM:CONSOLE)
Choose at the left side Configuration Properties - Linker - All Options , change both options at once and click OK.
11) Build and run the .exe with CTRL-F5. The application will be opened in a new window.
Now overwrite Source.asm with a 32-bit Console application:
.MODEL flat, stdcall
; https://docs.microsoft.com/en-us/cpp/assembler/masm/proto
GetStdHandle PROTO STDCALL, ; https://docs.microsoft.com/en-us/windows/console/getstdhandle
nStdHandle: SDWORD
WriteFile PROTO STDCALL, ; https://docs.microsoft.com/en-us/windows/desktop/api/fileapi/nf-fileapi-writefile
hFile: DWORD, ; output handle
lpBuffer: PTR BYTE, ; pointer to buffer
nNumberOfBytesToWrite: DWORD, ; size of buffer
lpNumberOfBytesWritten: PTR DWORD, ; num bytes written
lpOverlapped: PTR DWORD ; ptr to asynchronous info
ExitProcess PROTO STDCALL, ; https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-exitprocess
dwExitCode: DWORD ; return code
.DATA ; https://docs.microsoft.com/en-us/cpp/assembler/masm/dot-data
Hallo db "Hello world!",13,10
.DATA? ; https://docs.microsoft.com/en-us/cpp/assembler/masm/dot-data-q
lpNrOfChars dd ?
.CODE ; https://docs.microsoft.com/en-us/cpp/assembler/masm/dot-code
main PROC ; docs.microsoft.com/en-us/cpp/assembler/masm/proc
invoke GetStdHandle, -11 ; -> StdOut-Handle into EAX
invoke WriteFile, eax, OFFSET Hallo, LENGTHOF Hallo, OFFSET lpNrOfChars, 0
invoke ExitProcess, 0
main ENDP
END main ; https://docs.microsoft.com/en-us/cpp/assembler/masm/end-masm
Change the Solution Platforms to x86 (No. 8 above) and complete the project properties with SubSystem: Console (/SUBSYSTEM:CONSOLE) (No. 10 above). You must not set the Entry point, because ml32 expects the entry point after the END directive (END main). Build and run the .exe with CTRL-F5.