external assembly file in visual studio - visual-studio

Question

I searched and found I can not use __asm in x64 in visual studio. Instead I have to use an external assembly file.
How can I add external assembly file to my win32 console project?
How can compile them?
Can you explain step by step.

Answer 1

How to build a mixed-source x64-project with a x64 assembly file in Visual Studio:
1) Start Visual Studio (Community) 2015 and choose FILE - New - Project.
2) In the next window choose Win 32 Console Application.
3) You get a confirmation. Click on Next >.
4) In the next window you can accept the default settings. Click on Finish.
5) Make sure, that the project is highlighted in the Solution Explorer and and choose PROJECT - Build Customizations... from the menu.
6) In the next window tick masm(.targets,.props) and click on OK.
7) Choose Build - Configuration Manager...
8) Change the Active solution platform to x64
9) Create callee.asm: PROJECT - Add New Item.
10) In the next window choose C++File(.cpp) and - IMPORTANT! - give it a name with an .asm extension. Click on Add.
10) Now check if the .asm file has the right properties. In the Solution Explorer right-click on the file and choose Properties.
11) In the Property Page you should see at least:
Excluded From Build (empty) or No
Item Type Microsoft Macro Assembler
Under Command Line ensure that ml64.exe is chosen as the assembler.
Click on OK.
12) Now you can fill the files with content.
ConsoleApplication1.cpp:
#include <iostream>
using namespace std;
extern "C" void hello_from_asm();
int main()
{
cout << "Hello from CPP" << endl;
hello_from_asm();
return 0;
}
callee.asm:
PUBLIC hello_from_asm
EXTERN puts:PROC
.data
hello1 db "Hello from ASM.",0
.code
hello_from_asm PROC
push rbp
mov rbp, rsp
sub rsp, 32 ; Shadow Space
and spl, -16 ; Align stack at 16
lea rcx, hello1
call puts
leave ; Restore stack (rsp) & frame pointer (rbp)
ret
hello_from_asm ENDP
END
13) Build the .exe
and run it with CTRL-F5.
The application will be opened in a new window.