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NASM Forum => Using NASM => Topic started by: nobody on January 15, 2008, 03:10:00 AM

Title: Demo 11 and local variable
Post by: nobody on January 15, 2008, 03:10:00 AM

I'm experimenting with Nasm and I started with demo11 from your 2.0 distribution.
Im having problems using the latest proc macros. I'm used to Masm syntax and like the stile but have a hard time to make it work.

The example may illustrate:

entry   consol

[section .bss]
   fname:   resb 260
   lname:   resb 260
   age:      resd 1

[section .text]
CHAR Title, "My first console program"
proc   consol
LOCALS
LOCAL  pTitle, dword   ;local variable
ENDLOCALS



invoke printf, "Nasm Version %s%c%c",   __NASM_VER__,13,10
   invoke printf,"-----------------%c%c",13,10
   invoke printf,"%s%c%c%c%c", Title,13,10,13,10



invoke   printf, "First Name: "
   invoke  scanf, "%260s", fname
   invoke   printf, "Last Name: "
   invoke   scanf, "%260s", lname
   invoke   printf, "Age: "
   invoke   scanf, "%01d", age
   mov   eax, [age]
   if   eax, >=, 21
      invoke   printf, "Hello, %s %s! What are you having today?", fname, lname
   else
      invoke   printf, "Sorry kid, you're only %d !%c%c", [age],13,10
   endif

invoke   printf, "The Address of Title: %x%c%c", Title,13,10

;This is what I try to do:
   mov dword[ebp-4],fname
   invoke printf,"The string pointed at:  %s%c%c",[ebp-4],13,10

;This is what I thought it should be but dont work!
   mov dword[pTitle],Title   ;attemtet to store addr of Title in local var
   invoke printf,"The string pointed at:  %s%c%c",[pTitle],13,10

invoke   printf, "%c%c%c%cPress any key to exit.",13,10,13,10
   invoke   _getch
   xor   eax, eax
   ret
endproc

The question I have is this:
How do I address the local var by its name?
Masm syntax, lea eax pTitle don't work either

any help would be appreciated
tx Klod

Title: Re: Demo 11 and local variable
Post by: nobody on January 15, 2008, 09:30:28 PM

Doesn't look like anything you found at this site. Nasmx?

In what manner does it not work?

The "-e" switch or the "-l" switch may be helpful to see what this "hidden cruft" actually emits - if it'll assemble at all...

Good Luck,
Frank

Title: Re: Demo 11 and local variable
Post by: mcamember on January 15, 2008, 10:14:55 PM

Hi Klod
In this code :

mov dword[pTitle],Title  

you are trying to re-write something in .text which is the code
area. I think Windows forbids this.

You can make this work by moving the variable  "pTitle" out of
the .text section and into an initialized data section :

[section.data]
            pTitle dd 0


I think the LOCAL statement is for initializing variables in a code
area *but I'm not sure*. If so, then the variables would be read-only. I eliminated the LOCAL directives altogether.

What surprised me most was that        

mov dword[pTitle],Title  

actually worked. I would have thought a register would be required:

mov eax,pTitle
            mov dword [pTitle],eax

Live and learn!
Hope this helps.
mcamember

Title: Re: Demo 11 and local variable
Post by: mcamember on January 15, 2008, 10:26:17 PM

Of course that last code line *should* have read:

mov eax,Title <------
mov dword [pTitle],eax

;mcamember