Microsoft KB Archive/149746

= BUG: Access Violation Calling Exported Subroutine in DLL =

PSS ID Number: 149746

Article Last Modified on 11/2/1999

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The information in this article applies to:


 * Microsoft Fortran PowerStation for Windows 95 and Windows NT 4.0

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This article was previously published under Q149746



SYMPTOMS
When you use the !MS$ATTRIBUTES DLLEXPORT attribute to export a DLL's subroutine, and call that subroutine from another subroutine within the same DLL it causes the following Access Violation:

The instruction at "0x00000000" referenced memory at "0x00000000".

The memory could not be "written"



RESOLUTION
If you need to call an exported subroutine in a DLL, you should put this code into a non-exported helper subroutine and have the exported subroutine call the non-exported helper subroutine.



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.



Steps to Reproduce Problem
 Build the DLL using the sub.for file listed below. At the MS-DOS command-line prompt, type:

fl32 /LD sub.for

 Build the MAIN program using the main.for file listed below, and link it to the DLL static library file created in Step 1. At the same MS-DOS command-line prompt, type:

fl32 main.for sub.lib



MAIN
! filename: main.for ! Compile options needed: none program fortapp interface subroutine thesub !ms$attributes dllimport, stdcall :: thesub end subroutine end interface call thesub end program fortapp

DLL
! filename: sub.for ! Compile options needed: /LD subroutine thesub !ms$attributes dllexport, stdcall :: thesub interface subroutine othersub !ms$attributes dllexport, stdcall :: othersub end subroutine othersub end interface call othersub end subroutine subroutine othersub !ms$attributes dllexport, stdcall :: othersub end subroutine

Additional query words: 4.00

Keywords: kbLangFortran KB149746

Technology: kbAudDeveloper kbFORTRANPower400NT kbFortranSearch kbZNotKeyword8

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