BUG: Viewer Setup Causes Error in SYMTAB11.C

CAUSE

This error is generated when a setup script tries to replace a list item that is past the end of the list using ReplaceListItem.

The setup script shipped with Viewer, TITLE.MST, expects the value returned by GetWindowsDir() to be in uppercase letters. It contains the line:

   ReplaceListItem szExtras$, ASC(MID$(GetWindowsDir(), 1, 1)) -
         ASC("A") + 1, STR$(4096)
				

The MID$ function call creates a substring of length 1 and starting at position 1 of the string returned by GetWindowsDir(). This substring will be the drive letter of the drive from which Windows was started. The ASC function call generates the numeric ASCII code for this character. Then the numeric ASCII code for "A" is subtracted from this number. The script expects the result of this to be between 0 and 25, and it increments this number by 1 and uses it as an index into the szExtras$ list, which contains 26 items. If GetWindowsDir() returns an uppercase string, the result of the subtraction will indeed be between 0 and 25. However, if GetWindowsDir() returns a lowercase string, the result will be out of range.

The value returned by GetWindowsDir() would be lowercase if the PATH statement in the user's AUTOEXEC.BAT used lowercase for the name of the Windows directory.

You can see the value that would be returned by the GetWindowsDir() function by typing SET from an MS-DOS prompt in Windows, and checking the value of the "windir" environment variable. This environment variable is set by Windows when it starts up, and it has the same value as is returned by GetWindowsDir().

   ReplaceListItem szExtras$, ASC(MID$(GetWindowsDir(), 1, 1)) -
         ASC("A") + 1, STR$(4096)
				

   ReplaceListItem szExtras$, ASC(MID$(UCASE$
         (GetWindowsDir()), 1, 1)) - ASC("A") + 1, STR$(4096)