Q149516: BUG: Watching a DLL Common Block Using Context Operator Fails

Article: Q149516
Product(s): Microsoft Fortran Compiler
Version(s): 4.0
Operating System(s): 
Keyword(s): kbDebug kbidekbbuglist
Last Modified: 02-NOV-1999

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The information in this article applies to:

- Microsoft Fortran PowerStation for Windows 95 and Windows NT, version 4.0 
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SYMPTOMS
========

Attempting to view a DLL variable or common block contents in a watch window
using the context operator {} fails with the following messages:

DLL variable:

  "EE2347: Undefined variable"

DLL common block:

  "Invalid Debug Information"

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this problem and will post new
information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

Debug information for DLL variables and common blocks is available in the
debugger's Locals window. The members of a common block can be viewed in a watch
window but only if specified without the context operator. Trying to view a DLL
variable or common block by using the context operator will always fail. Also,
attempting to watch a common block structure in a watch window will fail with
the message "Invalid Debug Information".

Steps to Reproduce Problem
--------------------------

1. Create two source code files using the sample code provided. One (Theapp.for)
  will be the main source code and the other (Thedll.for) will be the DLL
  source code.

2. Create a QuickWin project using the main source file (Theapp.for). From the
  Developer Studio File menu, choose New, and then double-click the Project
  Workspace option. In the New Project Workspace dialog box, click the QuickWin
  Application type, name the project TheApp, set the project directory, and
  click the Create button.

3. Insert the main source code file into the project. From the Insert menu,
  choose Files into Project. and select the Theapp.for file.

4. Create a DLL project using the file Thedll.for, which will be a subproject of
  the QuickWin project created in step 2. From the Insert menu, choose Project,
  and then in the Insert Project dialog box, click the Dynamic-Link Library
  type, name the project TheDll, click Subprojects of:, and click the Create
  button.

5. Insert the DLL source code file into the subproject. From the Insert menu,
  choose Files into Project, and select the Thedll.for file.

6. Set the DLL build output directory to be the same as the QuickWin build
  output directory. From the Build menu, choose Settings, and then select the
  General folder tab. In the Settings For list box, highlight the DLL debug
  project target "TheDll - Win32 Debug (TheDll.dll)." Then select the Output
  files edit box, and remove the "TheDll\Debug" text, replacing it with
  "Debug." Then click the OK button to save the changes and exit the dialog
  box.

7. Build and link the QuickWin and DLL projects. In Developer Studio, change the
  default configuration to "TheApp - Win32 Debug." Then from the Build menu,
  choose Rebuild All.

8. Try to view the common block or its members in a watch window. Begin a
  debugging session, from the Build menu, choose Debug, and then select Step
  Into. Step past the variable initialization statements in the DLL. Now, in a
  watch window, type the variable "i" or the common block name "TheBlock" using
  the context operator as in the following examples and press the ENTER key.

  Example One
  -----------

  Type:

  " {,,TheDll.dll}i" (without the quotation marks)

  Result:

  This fails with "EE2347: Undefined variable"

  Example Two
  -----------

  Type:

  " {,,TheDll.dll}TheBlock" (without the quotation marks)

  Result:

  This fails with "Invalid Debug Information"

Sample Code
-----------

Main:

  C Compile options needed: /MW /Zi
  C TheApp.for (QuickWin app)
        program TheApp
            integer i, j
            common /TheBlock/ i, j
            !ms$attributes dllimport :: TheBlock
            call initcommon()
            print *, i, j
        end

DLL:

  C Compile options needed: /LD /Zi
  C TheDll.for (DLL for TheApp)
        subroutine initcommon()
            !ms$attributes dllexport :: initcommon
            integer i, j
            common /TheBlock/ i, j
            !ms$attributes dllexport :: TheBlock
            i = 5
            j = 7
        end

Additional query words: 4.00

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Keywords          : kbDebug kbide kbbuglist
Technology        : kbAudDeveloper kbPTProdChange kbFortranSearch kbFORTRANPower400NT
Version           : :4.0

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