flat assembler - ERR directive - useful ??? Conditional ERR

Index > Compiler Internals > ERR directive - useful ??? Conditional ERR

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DOS386

Joined: 08 Dec 2006
Posts: 1904

DOS386 07 Apr 2009, 01:54

Code:

  macro mov op1,op2 {
    if op1 eq cs
      err "CS is not a valid destination"
    end if
    if op1 in <ds,es,fs,gs,ss> & op2 in <cs,ds,es,fs,gs,ss>
      push  op2
      pop   op1
    else
      mov   op1,op2
    end if
  } ; endmacro

  mov es,ax
  mov ds,cs
  mov cs,ds ; BUG !!!

When compiling this in the commandline, I get 2 offending lines listed:

Code:

  mov cs,ds ; BUG !!!
      err "CS is not a valid destination"

telling me what's wrong ... but this not really the effect of err - if I place anything other like abortcompilationhere , the effect will be pretty same.

OTOH in the IDE, only

Code:

  mov cs,ds ; BUG !!!

gets listed and no clue what's wrong, and no benefit from err again. Shouldn't err pass the string to become useful ?

Other possibility of improvement:

Code:

  if ($>$FFFF)
    err "You ran out of UNreal CS limit"
  end if

could become:

Code:

  err ($>$FFFF)

would crash only if the expression is true and report the offending expression. Idea

07 Apr 2009, 01:54

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20758
Location: In your JS exploiting you and your system

revolution 07 Apr 2009, 02:01

The idea of err is that it is always guaranteed to give an error. Kind of like Intel making UD2 as an encoding to never be used by a valid instruction.

Last edited by revolution on 07 Apr 2009, 02:06; edited 1 time in total

07 Apr 2009, 02:01

DOS386

Joined: 08 Dec 2006
Posts: 1904

DOS386 07 Apr 2009, 02:04

revolution wrote:

The idea of err is that is it always guaranteed to give an error. Kind of like Intel making UD2 as an encoding to never be used by a valid instruction.

while abortcompilationhere could become valid one day Laughing

Code:

  conderr ($>$FFFF)

07 Apr 2009, 02:04

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20758
Location: In your JS exploiting you and your system

revolution 07 Apr 2009, 02:09

abortcompilationhere is too long to be friendly to use.

07 Apr 2009, 02:09

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8466
Location: Kraków, Poland

Tomasz Grysztar 07 Apr 2009, 05:10

And "abortcompilationhere" gives you a different error message, while ERR tells you that breaking the compilation was intended in that place.

07 Apr 2009, 05:10

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