Understanding Symbol Flags

The Symbol Service dialog box provides direct access to symbol flags and properties of functional objects that may be associated with them. The following symbol flag options are available:

Trace (Tr)

The Trace flag activates the tracing of any user-defined function (shown as a symbol within the Symbol Service window). Tracing will only occur when the symbol is a function, and the expression being evaluated uses the symbol name as a function (not as a local variable name, for example).

Protect Assign (Pa)

This flag intercepts attempts to assign values to protected symbols. For instance, the symbol pi is a protected symbol. All symbols that are the names of built-in AutoLISP functions are assignment-protected by default. See Protected Symbols for more information on symbol protection.

Note that symbol protection works only for explicit setq, set, or defun invocations. Binding a protected symbol in an argument list of a user-defined function is not intercepted.

Debug on Entry (De)

If this flag is set, a breakpoint occurs at each function invocation, regardless of whether the function was loaded with debugging information. The De flag is tested at each function invocation, not during load or defun execution.

Note that VLISP ignores the Debug-on-Entry flag for all SUBR and EXRXSUBR symbols.

Export to ACAD (Ea)

If the Ea flag is set, the function associated with this symbol is defined as an external subroutine. This makes the function available to ObjectARX applications.