DOCERR: Clarification of the /H Identifier Length Option

• The Microsoft C/C++ Compiler (CL.EXE) included with: - Microsoft C for MS-DOS, versions 6.0, 6.0a, 6.0ax - Microsoft C/C++ for MS-DOS, version 7.0 - Microsoft Visual C++ for Windows, versions 1.0, 1.5 - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 2.1, 4.0, 4.1,

       5.0
  

SUMMARY

In Microsoft C, the /H option is used to set the maximum length of identifiers. Using /H can only decrease the maximum allowable length of identifiers, not increase it. An identifier declared with the CDECL type has an underscore (_) appended to the front at compile time. This character is part of the identifier and takes a significant location. Therefore, the maximum length of an identifier declared with the standard C declaration syntax is 32 characters.

In C/C++ version 7.0, the default maximum length is also 32 characters. However, in this version, the /H option may be used to increase this to a maximum of 247 characters.

In Visual C++ 16-bit and Visual C++ 32-bit, there is no default maximum length--identifiers can be up to 2047 characters in length. Compiling a program with an identifier containing more than 2047 characters will generate fatal error C1064, compiler limit : token overflowed internal buffer.

MORE INFORMATION

The following example shows how using /H can actually introduce errors if identifier lengths are limited too much:

Sample Code

   /* When compiled with /H5, the following code will produce either
    *    error L2025: _func : symbol defined more than once
    *      -or-
    *   error LNK2005: _func already defined in '.obj file'
    *   fatal error LNK1169: one or more multiply defined symbols found
    */

   void func1(void);
   void func2(void);

   void main(void)
   {
        func1();
   }

   void func1(void)
   {
   }

   void func2(void)
   {
   }