Max Identifier Length May Cause Mixed C/MASM Conflict

• Microsoft Macro Assembler for MS-DOS, versions 5.1 and 5.1a
• Microsoft Macro Assembler for OS/2, versions 5.1 and 5.1a

SUMMARY

The Microsoft Macro Assembler (MASM) versions 5.1 and 5.1a allow identifiers to have a length of 31 characters. The Microsoft C Compiler versions 5.1, 6.0, and 6.0a also allow identifiers to have a length of up to 31 characters. However, the C compiler adds an implied leading underscore, which may make the total length of an identifier 32 characters.

The above limits may cause a problem when performing mixed-language programming where a C identifier that is 31-characters long needs to be recognized by a Macro Assembler module. The C identifier of 31 characters becomes 32 characters because of the added leading underscore, and the assembler can only recognize 31 characters. If this occurs, a "L2029: unresolved external" error will be generated by the linker when it does not locate a symbol with the truncated name.

MORE INFORMATION

To get the assembler routine to match the C identifier of 31 characters, you can do one of the following:

1. Use the .MODEL directive and specify the C language type. For example:

         .MODEL small,c  ; The C language type specifies C conventions
   

   The C language type specifies C naming and calling conventions. It will allow the use of a 31-character identifier and also add the implied leading underscore.

2. Modify the C program to shorten the length of the variable's name.

3. Update to Macro Assembler version 6.0. Identifiers may be up to 247 characters long with version 6.0.