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Macro question (hutch's jabs alternative)

oK hutch made a macro



jabs MACRO address

     push address

     retn

ENDM

that has the unfortunate side effect of messing up call/ret pairing :(

alternatively you could use



jabs MACRO address

     mov eax,address

     jmp eax

ENDM

but what if you cant spare any registers?

now im not interested in useing the direct jump oppcode I just want a macro so that I can type jabs address and it will work all the time..

So I made this one



jabs MACRO address

     push address

     add esp,4

     jmp DWORD PTR [esp-4]

ENDM

and i have used it successfully, I know that the stack is ESP+ and so I was hopeing that ESP- was unused,
anyway thats my question, will doing this work always? or are there some sitiation where esp- is used?

Posted on 2003-02-17 17:58:24 by dionysus

Macro question (hutch's jabs alternative)

I would call it creative thinking... looks good to me. The only thing i can say about it is this will make it very easy to write spagetti code and end up with very unpredictable errors (and error tracking), since its very easy to lose sight of what you dont see when your write code: the stack.

Those who use this macro better have an solid understanding of how functions are called, processed for params, and returned from.

:NaN:

Posted on 2003-02-17 22:36:29 by NaN

Macro question (hutch's jabs alternative)

jl32 MACRO address:REQ

    LOCAL jta

    jta = address - $ - 5

    db 0E9h

    dd jta

ENDM



ja32 MACRO address:REQ

    db 0E9h

    dd address

ENDM



jl8 MACRO address:REQ

    LOCAL jta

    jta = address - $ - 2

    db 0EBh

    db jta

ENDM



ja8 MACRO address:REQ

    db 0EBh

    db address

ENDM

this always works for me ^_^

use the macros postfixed with 32 for full displacement jumps and the 8 for 8 bit displacements. Use the 8 bit displacements if the jump if the range is -128 to +127 bytes, this will make your code smaller.

jl8 and jl32 (prefix: jl) - for labels E.G. jl8 label or jl32 label ... (but why would you want to use these macros when you can just simply use :: jmp label) ^_^

ja8 and ja32 (prefix: ja) - for absolute jumps E.G. ja32 31Fh or ja8 0Ch ... Don't forget to calculate the number of bytes to jump. MASM gives me an error if I start calculating for an absolute jump ( jta = address - $ - 2 ... ) - the same thing I did with labels.

:grin:

Posted on 2003-02-18 00:41:04 by arkane

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