DOCERR: "Guide to Programming" DLL Example Incorrect

 Last reviewed: July 23, 1997
Article ID: Q88140
3.10 WINDOWS kbtoolkbtoolg kbdocerr

The information in this article applies to:

  • Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

SUMMARY

In the "Guide to Programming" manual included with version 3.1 of the Microsoft Windows Software Development Kit (SDK), the dynamic-link library (DLL) example in Chapter 20 contains some errors. The text below lists these errors and the steps to correct them.

MORE INFORMATION

Pages 475 and 480 discuss the Windows exit procedure (WEP) that must be present in every DLL. The code on page 475 implies that the source code for the WEP function belongs in the same file as the source code for the other functions in the DLL. This implication is incorrect. Because the segment containing the WEP must be marked PRELOAD FIXED and the other segments of the DLL should be marked MOVEABLE DISCARDABLE, the source code for the WEP should be in a separate file, for example, WEP.C.

To correct this problem, name the code segment that contains the WEP by specifying the -NT option switch for the Microsoft C Compiler. The following compiles the code in the WEP.C file and places the resulting code into a code segment named WEP_SEG: 

   cl -c -AMw -Gsw -NT WEP_SEG -Os -W3 wep.c
Place a SEGMENTS statement in the module definition (.DEF) file to specify the attributes for the code segment that contains the WEP. The .DEF file should also include a CODE statement that specifies the default attributes for the code segments not listed in a SEGMENTS statement. The SEGMENTS statement is as follows: 

   SEGMENTS
      WEP_SEG PRELOAD FIXED
On page 481, the .DEF file names the library using a combination of uppercase and lowercase letters. Naming a library with lowercase letters causes problems if the DLL is used with version 3.0 of the Microsoft Windows graphical environment. These problems have been corrected in Windows 3.1.

Also on page 481, the HEAPSIZE statement in the .DEF file does not reserve any space for a heap for the DLL. This is incorrect. The DLL must have at least a minimal heap available for the functions in the C run-time library. Modify the HEAPSIZE statement to reserve 1024 bytes for the heap.

On pages 482 and 483, the small memory model is incorrectly specified in the C compiler command line. On pages 483 and 484, medium memory model libraries are correctly specified to link the DLL.

To correct this problem, modify the compiler command line to use the medium memory model libraries by replacing the -ASw option switch with the -AMw option switch.

To reflect the changes listed in this article, replace the .DEF file on page 481 with the following: 

   LIBRARY MINDLL
   DESCRIPTION 'MinDLL -- Minimum Code Required for DLL.'
   EXETYPE WINDOWS
   STUB 'WINSTUB.EXE'

   CODE MOVEABLE DISCARDABLE
   DATA MOVEABLE SINGLE
   SEGMENTS
      WEP_SEG PRELOAD FIXED

   HEAPSIZE 1024

   EXPORTS
      MinRoutine @1
      WEP        @2 RESIDENTNAME
To reflect the changes listed in this article, replace the makefile on pages 482 and 483 with the following: 

   all: mindll.dll

   mindll.obj: mindll.c
      cl -c -AMw -Gsw -Os -W3 mindll.c

   wep.obj: wep.c
      cl -c -AMw -Gsw -NT WEP_SEG -Os -W3 wep.c

   mindll.dll: mindll.obj wep.obj
      link mindll.obj libentry.obj wep.obj, mindll.dll, \
         mindll.map/map, mdllcew.lib libw.lib/noe/nod, mindll.def
      mapsym mindll.map
      implib mindll.lib mindll.def
      rc mindll.dll

Additional reference words: 3.10 docerr
KBCategory: kbprg kbdocerr
KBSubcategory: KrDll
Keywords : kb16bitonly

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Last reviewed: July 23, 1997
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