Pass arguments in an array.

[hutch--]

In this brave new world of mixed hybrid calling conventions, here is another one to add to the collection.

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;                              Pass procedure arguments in an array
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    include \masm32\include64\masm64rt.inc

    .code

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entry_point proc

    LOCAL arr[16] :QWORD                    ; create a QWORD array on the stack

    lea rcx, arr                            ; load its address into RCX
    mov QWORD PTR [rcx], 1
    mov QWORD PTR [rcx+8], 2
    mov QWORD PTR [rcx+16], 3
    mov QWORD PTR [rcx+24], 4
    mov QWORD PTR [rcx+32], 5
    mov QWORD PTR [rcx+40], 6
    mov QWORD PTR [rcx+48], 7
    mov QWORD PTR [rcx+56], 8
    call arrtest                            ; call the arrtest proc with address in RCX

    waitkey

    invoke ExitProcess,0

    ret

entry_point endp

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arrtest proc parr:QWORD

    LOCAL .r15 :QWORD

    mov [rbp+16], rcx                       ; copy RCX into parr address
    mov .r15, r15                           ; preserve r15

    mov r15, parr

    conout str$(QWORD PTR [r15]),lf
    conout str$(QWORD PTR [r15+8]),lf
    conout str$(QWORD PTR [r15+16]),lf
    conout str$(QWORD PTR [r15+24]),lf
    conout str$(QWORD PTR [r15+32]),lf
    conout str$(QWORD PTR [r15+40]),lf
    conout str$(QWORD PTR [r15+48]),lf
    conout str$(QWORD PTR [r15+56]),lf

    mov r15, .r15                           ; restore r15

    ret

arrtest endp

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    end

[jj2007]

Hmmm... where is the difference to passing a pointer to a STRUCT?

[sinsi]

Or

Code: [Select]

;assume stack is para aligned
push 8
push 7
push 6
push 5
push 4
push 3
push 2
push 1
mov rcx,rsp
sub rsp,32 ;maybe not needed?
call arrtest
add rsp,32+8*8 ;or reuse
16 array slots but only 8 filled?

[hutch--]

JJ,

> Hmmm... where is the difference to passing a pointer to a STRUCT?

Less typing.  :P Each has its place but with a long list of identical items, an array is simpler.

[hutch--]

 

> 16 array slots but only 8 filled?

Alway allows room for more.  :P

If you push the args you must correct the stack, either in the tail end of the called proc or after the procedure call. Writing to a RSP relative address does not have the problem and it allows for all integer data types from BYTE to QWORD.