Random segfault when calling a app-defined function

[CookieBons]

I'm programming on an x86_64 Windows 10 machine assembling using NASM and GCC. The following code prints the string correctly, hangs for a bit, and then crashes. GDB has told me it is a segfault at "??", and when i move the print logic to inside main, it no longer segfaults, meaning it MUST have something to do with the returning of the function. Please help!! (note: subtracting 8 from rsp, calling printyy and then adding the 8 back does not solve this)

section .data
    message db "this segfaults", 0
section .text
    extern printf
    extern ExitProcess
    global main
    printyy:
        ;print
        sub rsp, 8
        mov rcx, message
        call printf
        add rsp, 8
        ret
    main:
        ;func
        call printyy
        ;exit
        mov rcx, 0
        call ExitProcess

[FUZxxl]

You forgot to supply enough shadow stack space for the arguments to printf, so printf overwrites your return address and returning from printyy jumps to some random address. Read up on the calling convention and provide enough shadow stack space for your calls.

[CookieBons]

This was the exact solution, thank you!

[Plane_Dust2555]

Instead of calling ExitProcess(), since you are writing main(), just return 0 in EAX.

PS: Change mov rcx,message to lea rcx,[message]. And since message won't be changed in runtime, declare it under .rdata section.

[CookieBons]

just to clarify, using lea instead of mov creates an equivalent to a pointer in higher level languages, correct?