Agilent IO Libraries Known Limitations

• There is a memory leak in Windows 98 which may affect the IO Libraries operation.
  • We have observed a 4 Kb memory leak each time any program that dynamically links the Microsoft msvcrt.dll (even a program that does not do IO) is run and then exits on Windows 98.  This DLL is the C runtime library supplied with Microsoft Visual Studio and it is used by many products.
  • The IO Libraries dynamically link to msvcrt.dll so any program using SICL and / or Agilent VISA will exhibit this problem.
  • If your application involves starting and stopping programs many times, you will eventually run out of memory.  Windows 98 will gradually become sluggish and eventually quit.  The only solution to this problem is to reboot.
  • We are reporting this defect to Microsoft but there is no resolution yet available.
  • Note: If in Microsoft Visual Studio, you choose 'Multithreaded DLL' in the 'Use run-time library:' box on the C/C++ Code Generation tab, your application will dynamically load msvcrt.dll.

• We have observed problems with standby mode. You should turn off standby mode on your computer when using the IO Libraries. Do this using Control Panel, Power Options or Control Panel, Power Management.

• SICL for Windows 95, Windows 98 and Windows NT supports Microsoft Visual BASIC, but it does not support Visual BASIC for Applications included with applications such as Microsoft Excel.

• Using the Agilent 82335 GPIB interface with both SICL and the HP-IB Command Library at the same time on the same interface is not supported. No error will be reported but unexpected results could occur. Note that the Agilent 82335 GPIB interface is not supported on Windows NT.

• Calling iclose() on a session while an interrupt or SRQ handler is executing for that session can cause unexpected results. You should ensure that this cannot happen in your application.

• Multi-CPU operation (available on Windows NT and Windows 2000) is not supported, except on the E8491 IEEE 1394 to VXI Interface

• The calling of SICL and VISA functions from within a DLL entry-point function (e.g. DllMain) is not supported.  The SICL iopen call (which is also used from within a VISA viOpen call) creates an interrupt thread and waits for it to start.  Windows will not start the newly created thread until the entry-point function terminates and thus a deadlock will occur.  The following excerpt from the DllMain documentation on the July 1999 MDSN Library summarizes good programming practice for a DLL entry-point function (Refer to the MDSN Library for more detailed information.):

  Warning On attach, the body of your DLL entry-point function should perform only simple initialization tasks, such as setting up thread local storage (TLS), creating synchronization objects, and opening files. You must not call LoadLibrary in the entry-point function, because you may create dependency loops in the DLL load order. This can result in a DLL being used before the system has executed its initialization code. Similarly, you must not call the FreeLibrary function in the entry-point function on detach, because this can result in a DLL being used after the system has executed its termination code. Calling Win32 functions other than TLS, object-creation, and file functions may result in problems that are difficult to diagnose. For example, calling User, Shell, COM, RPC, and Windows Sockets functions (or any functions that call these functions) can cause access violation errors, because their DLLs call LoadLibrary to load other system components. While it is acceptable to create synchronization objects in DllMain, you should not perform synchronization in DllMain (or a function called by DllMain) because all calls to DllMain are serialized. Waiting on synchronization objects in DllMain can cause a deadlock. To provide more complex initialization, create an initialization routine for the DLL. You can require applications to call the initialization routine before calling any other routines in the DLL. Otherwise, you can have the initialization routine create a named mutex, and have each routine in the DLL call the initialization routine if the mutex does not exist.

• If you uninstall the IO Libraries, I-SCPI support files needed by Agilent's VXIplug&play drivers are also removed.  If you then install another vendor's VISA, you will need to reinstall your Agilent VXIplug&play drivers before they can be used.

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