Failure to Load Resources When All File Handles Are Used (50741)

SUMMARY

A Windows-based application should not use all available file handles. Doing so may prevent Windows from being able to load the application's resources.

When Windows has to open the application's .EXE file to retrieve a resource (such as the icon's bitmap), it uses one of the application's file handles. If the application has used all available file handles, Windows cannot load the resource.

For example, suppose LoadIcon() was called previously to obtain an icon handle successfully, and the icon is being used as a window's icon. The rendering of the icon will fail if the application is using all the file handles. For example, if the window is to be minimized, the icon will be displayed as a black block on the screen.

NOTE: LoadIcon() loads in the logical information of the icon; the bitmap of the icon is not loaded until it is going to be used.

Under MS-DOS, an application has 20 file handles when it begins executing. Five of these handles (that is, STDIN, STDOUT, STDPRN, STDERR, and STDAUX) are automatically opened for use by the operating system. This leaves a total of 15 file handles available for an application. If a Windows-based application needs more file handles open at any given time, it can use the SetHandleCount() API.