LINK QB & C "Unresolved Externals"; How to Use LINK /NOE, /NOD (30271)

MORE INFORMATION

1. Notes for using LINK /NOE Option are as follows:
   
   The LINK /NOE option is required for interlanguage calling to eliminate the following error message:
   xx.LIB : error L2044: __xxxxx : symbol multiply defined, use /NOE
   The Microsoft language libraries, such as LLIBCE.LIB from C and BRUN40.LIB from QuickBasic, contain some of the same routines; thus, they require LINK /NOE.
   
   If you still get a "symbol multiply defined" message after using the LINK /NOE option, then the multiply defined symbols in your source code need to be renamed, recompiled, and relinked.
   
   The /NOE option is documented only in the README.DOC file on a disk in QuickBasic 4.00 and 4.00b and in Basic compiler 6.00 and 6.00b. In QuickBasic Version 4.50, /NOE is documented on Page 365 of the "Microsoft QuickBasic 4.5: Programming in Basic" manual.
2. Notes for using LINK /NOD Option are as follows:
   
   Note that an .OBJ file compiled with QuickBasic 4.00, 4.00b, or 4.50, or C 5.00 or 5.10 contains information telling the linker what .LIB file to look for at link time.
   
   If you use the LINK /NOD option, you are telling the linker not to search any specified library in the .OBJ file to resolve external references. Thus, if you use the /NOD option, you must explicitly specify the name of the .LIB language libraries for both C and QuickBasic in the LINK command (even if the .LIB library has a path set to it with SET LIB=path). If you do not, LINK.EXE will give the following error:
   LINK : error L2029: Unresolved Externals

Code Example

1. Compile cf.bas and cfunc.c (shown farther below) as follows:

   BC CF.BAS;
   CL /C /AL CFUNC.C

   You may also use the C medium-memory model: CL /C /AM CFUNC.C. This example uses CL.EXE from Microsoft C Versions 5.00 and 5.10.
2. Type SET at the DOS command line to make sure that you issued a statement similar to "SET LIB=C:\QB.400;C:\C.500" to tell LINK.EXE where to look for .LIB files at link time.
3. Link the Basic and C routines, specifying the Basic routine first and using LINK.EXE Version 3.61 or later:

   LINK CF.OBJ+CFUNC.OBJ/NOE;

CF.BAS

   REM  Basic routine cf.bas:
   DEFINT A-Z
   DECLARE SUB cfunc CDECL (BYVAL x AS INTEGER)
   beforecall = SETMEM(-2048)
   cfunc (1024)
   aftercall = SETMEM(3500)
   IF aftercall <= beforecall THEN PRINT "memory not reallocated."
   END
				

CFUNC.C

   /*  C routine cfunc.c:    */ 
   void far cfunc(bytes)
   int bytes;
   {
    char *malloc();
    char *workspace;
    workspace=malloc((unsigned) bytes);
    free(workspace);
   }