TCHAR as label

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ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 15 Nov 2011, 23:46

Code:

include 'win32a.inc'

TCHAR:

mov eax,[TCHAR] ;(A) ok, does compile

jmp TCHAR       ;(B) does not compile (invalid operand)

(A) does compile, but (B) does not compile ... I am surprised.
I can understand that the compiler does not allow both cases ...
but one and not the other, I don't understand.
Can anyone tell me why? Thank you in advance.

yes, I know that "TCHAR" is a macro.
It is precisely for this reason I am surprised that "A" does compile and not "B".

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15 Nov 2011, 23:46

revolution
When all else fails, read the source

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Location: In your JS exploiting you and your system

revolution 16 Nov 2011, 00:17

ouadji wrote:

yes, I know that "TCHAR" is a macro.

Therein lies the problem. TCHAR is not a macro, it is a structure.

16 Nov 2011, 00:17

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 16 Nov 2011, 00:22

Code:

struc TCHAR [val] { common match any, val \{ . db val \}
                           match , val \{ . db ? \} }

Indeed revolution, "TCHAR" is a structure
sorry for this mistake.

that said, I think a "struc" is a "macro"

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16 Nov 2011, 00:22

revolution
When all else fails, read the source

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Location: In your JS exploiting you and your system

revolution 16 Nov 2011, 00:52

A structure is a different from a macro in that it requires a leading label, whereas a macro cannot have a leading label.

Code:

macro ABC {do something}
struc ABC {do something else}
;
       ABC ;macro instantiation
label1 ABC ;structure instantiation
;
jmp TCHAR ;TCHAR structure with "jmp" as the label

Last edited by revolution on 16 Nov 2011, 01:03; edited 1 time in total

16 Nov 2011, 00:52

revolution
When all else fails, read the source

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Posts: 20451
Location: In your JS exploiting you and your system

revolution 16 Nov 2011, 00:56

BTW: Why you no look at the error messages? Mad

Code:

jmp TCHAR       ;(B) does not compile (invalid operand)
C:\Documents and Settings\We are the Borg\Our Documents\include/win32a.inc [12] TCHAR [1]:
                           match , val \{ . db ? \} }
C:\Documents and Settings\We are the Borg\Our Documents\include/win32a.inc [12] match [0]:
                           match , val \{ . db ? \} }
error: invalid operand.

16 Nov 2011, 00:56

typedef

Joined: 25 Jul 2010
Posts: 2909
Location: 0x77760000

typedef 16 Nov 2011, 01:29

Code:

jmp TCHAR

is the same as

Code:

jmp DWORD

LAUGH OUT LOUD x 2

16 Nov 2011, 01:29

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 16 Nov 2011, 09:10

of course i look at the error messages.
What I didn't understand was that "A" does compile and "B" does not.
Now I understand why. Thank you revolution

typedef: not "jmp dword", but "jmp byte" (a dword and a byte are two different things, do you know that ?) Wink

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16 Nov 2011, 09:10

revolution
When all else fails, read the source

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revolution 16 Nov 2011, 09:42

BTW: In case you are wondering how to do what you wanted:

Code:

jmp short TCHAR

Although I would not really encourage using things like TCHAR as label names. It all gets very confusing when you do that.

16 Nov 2011, 09:42

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 16 Nov 2011, 10:23

Quote:

Although I would not really encourage using things like TCHAR as label names.
It all gets very confusing when you do that.

Of course, it was just a theoretical reflection.
(in the context of wink improvement)

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16 Nov 2011, 10:23

typedef

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typedef 16 Nov 2011, 19:18

ouadji wrote:

typedef: not "jmp dword", but "jmp byte" (a dword and a byte are two different things, do you know that ?)

Ok, here's a better one maybe you have hard time with comparisons, or you just make quantitative judgements.

Code:

JMP [DATA_TYPE]

Clearly, "DATA_TYPE" is a compiler reserved keyword.

STILL, LAUGH OUT LOUD

16 Nov 2011, 19:18

revolution
When all else fails, read the source

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Location: In your JS exploiting you and your system

revolution 16 Nov 2011, 19:28

typedef wrote:

Clearly, "DATA_TYPE" is a compiler reserved keyword.

TCHAR is not a compiler reserved keyword. It is defined in win32a.inc as a structure. If you decide not to include win32a.inc then you are free to use TCHAR as you please for other things.

16 Nov 2011, 19:28

typedef

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Posts: 2909
Location: 0x77760000

typedef 16 Nov 2011, 20:32

revolution wrote:

typedef wrote:
Clearly, "DATA_TYPE" is a compiler reserved keyword.
TCHAR is not a compiler reserved keyword. It is defined in win32a.inc as a structure. If you decide not to include win32a.inc then you are free to use TCHAR as you please for other things.

But if you include win32a.inc, it becomes reserved doesn't it ?

LOL

16 Nov 2011, 20:32

revolution
When all else fails, read the source

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Location: In your JS exploiting you and your system

revolution 16 Nov 2011, 21:14

typedef wrote:

But if you include win32a.inc, it becomes reserved doesn't it ?

No. You can always make a label the same name as a macro or struc. Also you can use restruc to clear the structure at any time.

16 Nov 2011, 21:14

ouadji

Joined: 24 Dec 2008
Posts: 1081
Location: Belgium

ouadji 16 Nov 2011, 21:51

if "TCHAR" is a compiler reserved word, "tchar" should be one too.
However, it's not the case.

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16 Nov 2011, 21:51

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8359
Location: Kraków, Poland

Tomasz Grysztar 20 Nov 2011, 01:04

TCHAR is not a reserved word. It gets defined in some Win32 macroinstructions, but since preprocessor in fasm is case-sensitive, you get "TCHAR" expanded as macro/struc, while "tchar" is not recognized as a macro (but you may as well define another macro called "tchar" which will get expanded in "tchar" places).

20 Nov 2011, 01:04

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