Match around include

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DimonSoft

Joined: 03 Mar 2010
Posts: 1228
Location: Belarus

DimonSoft 03 Jul 2020, 19:09

Suppose we have the following main.asm file:

Code:

match ! , abc
{
  include 'library.inc'
}

and the following library.inc file:

Code:

What I see is that the ! symbol is defined as itself in library.inc although I personally would expect it to be abc.

Current behaviour can definitely be overriden by putting the match into the library.inc but, as one might guess, it’s an attempt to simplify unit management, and that would require wrapping it into a more meaningfully-named macro at the beginning and using a fix directive for the closing }. Besides that would require additional level of {} escaping inside the unit which is not quite convenient.

I wonder if this behaviour is intended and if it is, it would be good to know about the reasoning behind it.

03 Jul 2020, 19:09

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20401
Location: In your JS exploiting you and your system

revolution 04 Jul 2020, 01:37

The macro is expanded before the stuff inside is processed. So the match will find-and-replace all !'s in the single line "include 'library.inc'". Since there are no instances of ! in that line then it has no effect.

04 Jul 2020, 01:37

DimonSoft

Joined: 03 Mar 2010
Posts: 1228
Location: Belarus

DimonSoft 04 Jul 2020, 07:59

And since it is processed line by line it is impossible to inject some symbolic value from outside the file being included, right? I mean, it’s impossible to expand include before the outer match gets processed, isn’t it?

The workaround might be to use equ for the symbol but I’m not quite sure if it is completely equivalent. Requires much more attention to restore it properly while match would make FASM check for balanced {}.

04 Jul 2020, 07:59

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20401
Location: In your JS exploiting you and your system

revolution 04 Jul 2020, 08:10

You can use equ

Code:

! equ int3
include 'test.inc'

Code:

~ fasm test.asm && hd test.bin
flat assembler  version 1.73.08  (4053744 kilobytes memory)
1 passes, 1 bytes.
00000000  cc                                                |.|
00000001
~

And enclose it in a macro

Code:

macro my_include file, var, replacement {
  var equ replacement
  include file
  restore var
}
my_include 'test.inc', !, int3

04 Jul 2020, 08:10

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