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

ID: Q38216

The information in this article applies to:

Microsoft Macro Assembler for MS-DOS, versions 5.0, 5.1, 5.1a, 6.0, 6.0a, 6.0b
Microsoft Macro Assembler for OS/2, versions 5.0, 5.1, 5.1a, 6.0, 6.0a, 6.0b

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

Keywords :
Version : :5.0,5.1,5.1a,6.0,6.0a,6.0b
Platform :
Issue type :