Q38216: PRB: Possible Cause of L2002 for Mixed C, MASM in Large Model

Article: Q38216
Product(s): Microsoft Macro Assembler
Version(s): 5.0,5.1,5.1a,6.0,6.0a,6.0b
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

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The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 5.0, 5.1, 5.1a, 6.0, 6.0a, 6.0b 
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SYMPTOMS
========

If a variable is referenced externally in an assembler routine in the following
manner:

     .model large, c

     .data
     EXTRN Var:WORD

and declared globally in a large model C program as follows:

     int Var;

the following error is generated:

  error L2002: fixup overflow

CAUSE
=====

This error occurs because the assembler would expect to find Var in the segment
_DATA in DGROUP. The C declaration, however, will put var in the segment
FAR_BSS, since it is an uninitialized global data item in the large memory
model.

Note that the same is true for the compact memory model.

RESOLUTION
==========

One way to eliminate this error is to initialize Var in the C code:

     int Var=0;

This will put it in the _DATA logical segment in DGROUP.

Another work-around is to delcare Var in the Assembly code so that the assembler
would expect to find Var in FAR_BSS, as follows:

     .model large, c

     .fardata?
     EXTERN Var:WORD

In addition, be sure to use a segment override to access Var:

     MOV ax, SEG Var
     MOV es, ax
     MOV bx, es:Var

Additional query words: 5.00 5.10 5.10a 6.00 6.00a 6.00b

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Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM510 kbMASM600 kbMASM500 kbMASM600a kbMASM510a kbMASM600b
Version           : :5.0,5.1,5.1a,6.0,6.0a,6.0b

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