Trouble with MASM macro system

[key2k3]

Apparently, it's impossible to resolve macro arguments indirectly when inside a FOR-Block.
Let me demonstrate this:

Code Select Expand


test MACRO _Eax:=<>, _Ebx:=<>, _Ecx:=<>, _Edx:=<>, _Edi:=<>, _Esi:=<>, _Eip:=<>, _Esp:=<>
...
assume eax :PTR CONTEXT
  FOR tmp, <__Eax, __Ebx, __Ecx, __Edx, __Edi, __Esi, __Eip, __Esp>
%   IFNB @SubStr(tmp, 2)
      mov @CatStr(<[eax].reg>, @SubStr(tmp, 2)), %@SubStr(tmp, 2)
    ENDIF
  ENDM
...
ENDM


The macro is supposed to fill a CONTEXT structure, as you can see. I had to
use two underscores for the arguments in the loop because otherwise they would
be evaluated in-place.

I don't know if the MOV line really is correct, but it doesn't even get there. IFNB throws
an error A2006 "undefined symbol" although these are the symbols that were passed
to the macro (e.g. _Eax  ... I checked this with ECHO).

However, it works when I would write this inside the FOR loop

Code Select Expand


IFNB <_Eax>


I've also tried numerous workarounds but it started telling me "macro nesting to deep"
and now - a few hours later - I'm giving up. I'm really frustrated from this problem
that looks so simple!

Thanks for ANY suggestion(s).

Regards
- Key2k3 -

[drizz]

no sweat when you separate text from arguments/variables

Code Select Expand


fillcontext MACRO _Eax,_Ebx,_Ecx,_Edx,_Edi,_Esi,_Eip,_Esp
LOCAL regstxt,arg,counter
ASSUME EAX:PTR CONTEXT
counter = 0
regstxt textequ <EaxEbxEcxEdxEdiEsiEipEsp>
FOR arg,<_Eax,_Ebx,_Ecx,_Edx,_Edi,_Esi,_Eip,_Esp>
IFNB <arg>
MOV @CatStr(<[EAX].reg>,@SubStr(%regstxt,%counter*3+1,3)),arg
ENDIF
counter = counter + 1
ENDM
ASSUME EAX:NOTHING
ENDM


:boohoo: have fun,
drizz

[MazeGen]

key2k3, if you want to debug macros, learn how to use assembly listing (command-line option /Fl). This way you can see macro expansion and each iteration of any loops.

[key2k3]

@drizz: Thanks for the workaround, at least it's possible *somehow*.
@MazeGen: Thanks to you as well, I'm using this directive already but it didn't help me here.

So does MASM resolve symbols in one single pass only? It knows about the symbols when I write
them but does not know when the name is generated by another macro.

This should be a bug then, shouldn't it?

[MazeGen]

I'm not sure what exactly is unclear for you, but let me start here.

I try to call your macro test1 with no arguments. Look at the listing:

Code Select Expand

00000000 .CODE
00000000 Start:
test1
     1
     1 assume eax :PTR CONTEXT
     1   FOR tmp, <__Eax, __Ebx, __Ecx, __Edx, __Edi, __Esi, __Eip, __Esp>
     1 %   IFNB @SubStr(tmp, 2)
     1       mov @CatStr(<[eax].reg>, @SubStr(tmp, 2)), %@SubStr(tmp, 2)
     1     ENDIF
     1   ENDM
     2 %   IFNB @SubStr(__Eax, 2)
tmp1.asm(22) : error A2006: undefined symbol : _Eax
MacroLoop(1): iteration 1: Macro Called From
  test1(7): Macro Called From
   tmp1.asm(22): Main Line Code


There's nothing like _Eax, because using _Eax:=<> you say "if there is no _Eax argument, pass a blank argument (nothing)". Because _Eax is not required, the assembler can't know something like _Eax in this case. (Sorry for my english, I'm not sure if  one can understand something from my description).

drizz's solution does seem to be clear and correct, doesn't it?

[key2k3]

MazeGen wrote:
> There's nothing like _Eax, because using _Eax:=<> you say
> "if there is no _Eax argument, pass a blank argument (nothing)".

_Eax is defined ! It has no content, but it is defined. So you can e.g. write ...

IFNB <_Eax>

... inside the macro and it will work: it executes the block if no argument was
passed for _Eax.

> drizz's solution does seem to be clear and correct, doesn't it?

It works, but it involves some more code, which is contraproductive. MASM
is not able to resolve defined symbols whose names are generated at macro
run-time... THIS is the problem, because it should work normally!

Regards,
- key2k3 -

[MazeGen]

I think about it same way as in case of run-time procedures with variable argument count: If you don't pass an optional argument to such procedure, you can't read it, because it is not present.

Your macro procedure has variable argument count too. You can't read _Eax, if it is not present.

Just take it like my point of view. :8)