nasm_win64_dll_info

[test.asm]
[BITS 64]
            section .code
            global foo
            export foo
foo:
			push rbp
			mov rbp, rsp
			mov rbx, rcx
			add rbx, 3
            mov rax, rbx
            pop rbp
            ret

	global DllMain@16
DllMain@16:
			ret


[testdll.c]
#include <inttypes.h>
#include <windows.h>
#include <stdio.h>

typedef uint64_t (*tFoo)(uint64_t);

int main(int argc, char **argv) {
	tFoo foo;
	HMODULE testmodule = LoadLibrary("test.dll");
	if ( !testmodule ) {
		printf("Cannot load test.dll!\n");
		return -1;
	}
	foo = (tFoo)GetProcAddress(testmodule, "foo");
	if ( !foo ) {
		printf("Cannot find foo function!");
		return -1;
	}
	printf("foo() = %d\n", foo((uint64_t)34));
	return 0;
}

[commands]
nasm -f win64 test.asm -o test.obj
/cross/mxe/usr/bin/x86_64-w64-mingw32.shared-ld test.obj -o test.dll
/cross/mxe/usr/bin/x86_64-w64-mingw32.shared-gcc testdll.c -o testdll.exe