Suppressing "Cannot Find MYDLL.DLL" Error Box

ID: Q111610

The information in this article applies to:

Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1

SUMMARY

When explicitly loading a dynamic-link library (DLL) using LoadLibrary(), Windows will display a "file error" message box with the error

Cannot find MYDLL.DLL

where MYDLL.DLL is the name of the DLL specified in LoadLibrary() before returning from LoadLibrary() if the DLL does not exist in the Windows path. For more information about the Windows path, see the Windows search order described in the documentation for LoadLibrary().

It is possible to suppress this error message so that a custom error message or other error handling may be implemented without this system error box. To do so, call SetErrorMode() with SEM_NOOPENFILEERRORBOX before the call to LoadLibrary(). LoadLibrary() will return error code 2 meaning "File was not found."

MORE INFORMATION

SetErrorMode() only affects the error mode of the current task and does not affect the entire system. The return value may be used to toggle the error mode in different portions of an application.

For an implicitly loaded DLL that may be missing, the system will display the aforementioned error box if the application is run from Program Manager. After clicking the OK button, the following message appears:

Cannot find file d:\path\myexe.exe (or one of its components).
Check to ensure the path and filename are correct and that all required libraries are available.

From File Manager, no "file error" message box appears, but the following message is displayed instead:

File manager cannot find the specified file (or one of its components).

Make sure the path and filename are correct and that all required libraries are available.

Because these error messages appear before the WinMain() of the application executes, SetErrorMode() cannot suppress the error message boxes for implicitly linked DLLs. Furthermore, there is no way to configure Program Manager to suppress the "file error" message box.

Sample Code


 {
 HINSTANCE hDLL;
 UINT uOldErrorMode;

 uOldErrorMode = SetErrorMode(SEM_NOOPENFILEERRORBOX);

 // Try to load DLL.
 hDLL = LoadLibrary("MYDLL.DLL");

 if (hDLL == 2)
    MessageBox(NULL, "MYDLL.DLL does not exist", "ERROR", MB_OK);
 else if (hDLL <= HINSTANCE_ERROR)
    MessageBox(NULL, "Other problems loading MYDLL.DLL, "ERROR", MB_OK);
 else
 {
    MessageBox(NULL, "MYDLL.DLL exists", "SUCCESS", MB_OK);
    FreeLibrary(hDLL);
 }

 SetErrorMode(uOldErrorMode);  // Can restore error mode if desired.
 }

Additional query words: 3.00 3.10

Keywords : kb16bitonly
Version : WINDOWS:3.0,3.1
Platform : WINDOWS
Issue type :