macro duplicated args no error message,

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lazer1

Joined: 24 Jan 2006
Posts: 185

lazer1 17 Jun 2007, 01:02

fasm doesnt give any error messages if a macro
has 2 args with the same name,

eg

Code:

macro  xyz a,a
  {
  mov a, a
  }

xyz eax, eax

no error message,

I think that is an error codition,

17 Jun 2007, 01:02

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 17 Jun 2007, 01:39

[edit]Save your time skipping this senseless post and continue reading from the post below this one.[/edit]

Why do you think it is wrong?? "mov eax, eax" is perfectly valid (even though it just do nothing). However are other instructions where using the same operand has effect, for example sub and xor which has the effect of clearing the operand and add which has the effect of multiply the operand by two. Obviously there are others but I think that those are enough examples Wink

If you want to trap when both operands are the same check http://flatassembler.net/docs.php?article=manual#2.2.2 (the "eq" operator)

Last edited by LocoDelAssembly on 17 Jun 2007, 15:38; edited 1 time in total

17 Jun 2007, 01:39

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20445
Location: In your JS exploiting you and your system

revolution 17 Jun 2007, 12:37

What happens if you do this:?

Code:

macro  xyz a,a
  {
  mov a, a
  }

xyz eax, ebx

17 Jun 2007, 12:37

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 17 Jun 2007, 15:36

I never realized that he means that the formal parameters names are the same Embarassed

With that code it produces "mov ebx, ebx" so it uses the rightmost value. If you only supply one actual parameter then it tries to assemble "mov ," because the last value of a was void.

Sorry for my very silly post above

17 Jun 2007, 15:36

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 17 Jun 2007, 17:48

i think i even mentioned this in my old preprocessor tutorial Wink

17 Jun 2007, 17:48

lazer1

Joined: 24 Jan 2006
Posts: 185

lazer1 17 Jun 2007, 20:02

revolution wrote:

What happens if you do this:?

Code:

macro  xyz a,a
  {
  mov a, a
  }

xyz eax, ebx

that is a better example of the problem,

I had a header file with many macros, and my code kept
echoing 0 when it was supposed to echo nonzero,

after much debugging I realised the problem must be in
the macro, careful scrutiny revealed that
arg 3 and arg 6 of a 6 arg macro had the same name,

if you arent thinking about this specific problem then
you might not notice it in a macro with many args.

so I think fasm needs to regard this as an error,

duplicated arg names serves no purpose: no point
having an arg you cannot reference eg in your
example above the "ebx" cannot be referenced to

so it must be an error condition,

17 Jun 2007, 20:02

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