ASM Community

If I use esi, edi, and ebx in a proc instead of a variable (LOCAL or data?) do I have to zero it before I use it next time? example:

                                        ; open treeview data file for read    

    push    0                           ;

    push    FILE_ATTRIBUTE_NORMAL or\   ;

            FILE_FLAG_SEQUENTIAL_SCAN   ;

    push    OPEN_EXISTING               ;

    push    0                           ;

    push    0                           ;

    push    GENERIC_READ                ;

    push    DataFile                    ;

    call    CreateFile                  ;

    mov     esi, eax                    ; save file handle

    

    push    0                           ; Get file size for buffer

    push    esi                         ; file handle

    call    GetFileSize                 ;

    mov     ebx, eax                    ; save file size

    

    push    esi                         ; file handle to close

    call    CloseHandle                 ;

                                        

                                        ; Allocate a buffer to read file into    

    push    ebx                         ; file size

    push    HEAP_ZERO_MEMORY            ;

    push    hHeap                       ;

    call    HeapAlloc                   ;

    mov     hTempBuf, eax               ; save memory block pointer

    

                                        ; Get all sections and load into memory

    invoke  GetPrivateProfileSectionNames, addr hTempBuf, ebx, addr DataConfiglPath

         

    lea     esi, hTempBuf               ; do I have to xor esi before I do this?????

as I am still learning and many docs don't cover what questions I have, this board is invaluable to me! Since I used esi as the file handle, do I have to/ should I zero esi before I lea hTempBuf into it? As of now, I am not and all seems to work on Win98 and 2K but if it is wrong, I would like to fix it....

TIA

you should zero a container (for a return value) if its value has any significance and you need to be absolutely sure.

e.g. a call to a routine returns 00 when failed (but you're not sure the routine is implemented correctly by its programmer) then you zero out first before you call so that you'll always get at least zero in case of non-success. (else you might get whatever was in there to begin with)

here the lea will fill your register and lea is known to work (;) ) so it's not necessary to zero it first.

JC, where are the rest of your drinking tips?

Ok, so I only zero a register for a return value if I want one? (and if I want zero as a return) otherwise, I don't have to zero a register cause I will overwrite what is in it?

Ok, that helps.

Thanks.....

he passed out after the first tip :grin:

From alcohol or loss of blood?:grin:


Or both?:eek: