the simplest 64bit app won't start

[ramguru]

ha-ha actually I was focusing on goasm starting yesterday. Indeed it has the most complete & user friendly 64bit support. Though I have to say documentation could be neater :} .. and lack of examples (just invoke MessageBox), but that's allright..
BTW I've found another bad poasm (x64) feature that was the last drop :}
let's assume we have the following code:

Code Select Expand


foo proc bla1:QWORD, bla2:QWORD
   LOCAL hamster:QWORD

    ; bla1, bla2 are valid here
    invoke MessageBox,...
    ; bla1, bla2 become invalid here
    mov r10, bla1 ; --> mov r10, rcx
foo endp


It's simple really - poasm doesn't write any parameter to stack .. so they are lost if not preserved manually

[drizz]

That's what param area is for....

[ramguru]

So this is the actual code:

Code Select Expand


foo proc bla1:QWORD, bla2:QWORD PARMAREA=4*QWORD
LOCAL hamster:QWORD

mov    rcx, bla1
invoke MessageBox, 0, 0, 0, 0
mov    rcx, bla1

ret
foo endp

And this is it's disassembly

Code Select Expand


sub_140001028   proc near               ; CODE XREF: start+12
                sub     rsp, 38h
                mov     rcx, rcx
                mov     r9, 0           ; uType
                mov     r8, 0           ; lpCaption
                mov     rdx, 0          ; lpText
                mov     rcx, 0          ; hWnd
                call    MessageBoxA
                mov     rcx, rcx
                add     rsp, 38h
                retn
sub_140001028   endp



It's not like I haven't checked before stating my opinion..

[drizz]

In ML64 arguments evaluate to stack and in poasm to Registers, so in ML64 you can save them with "mov bla1,rcx"
I don't know if there is an easy way to access param stack area with poasm, it's probably a good idea to ask Pelle about that.