Used in conjunction with Mule support. This doesn't currently work. Compile with support for debugging XEmacs. Compile with internal error-checking added. Causes noticeable loss of speed.
Valid types are extents, bufpos, malloc, gc, typecheck.
Causes a small code increase but no loss of speed. Only use during development. Only works with some systems and compilers. The default is to not do clash detection. Note that we recommend against explicitly setting any of these variables.