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Tcl_SaveInterpState(3)	     Tcl Library Procedures	  Tcl_SaveInterpState(3)

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NAME
     Tcl_SaveInterpState,  Tcl_RestoreInterpState, Tcl_DiscardInterpState - save
     and restore an interpreter's state

SYNOPSIS
     #include <tcl.h>

     Tcl_InterpState
     Tcl_SaveInterpState(interp, status)

     int
     Tcl_RestoreInterpState(interp, state)

     Tcl_DiscardInterpState(state)

ARGUMENTS
     Tcl_Interp *interp (in)		    Interpreter for which  state  should
					    be saved.

     int status (in)			    Return code value to save as part of
					    interpreter state.

     Tcl_InterpState state (in) 	    Saved  state token to be restored or
					    discarded.
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DESCRIPTION
     These routines allows a C procedure to take a snapshot of the current state
     of an interpreter so that it can be restored after a call	to  Tcl_Eval  or
     some other routine that modifies the interpreter state.

     Tcl_SaveInterpState stores a snapshot of the interpreter state in an opaque
     token returned by Tcl_SaveInterpState.  That token value may then be passed
     back  to one of Tcl_RestoreInterpState or Tcl_DiscardInterpState, depending
     on whether the interp state is to be restored.  So long as one of the  lat-
     ter two routines is called, Tcl will take care of memory management.

     Tcl_SaveInterpState takes a snapshot of those portions of interpreter state
     that make up the full result of script evaluation.  This include the inter-
     preter  result,  the return code (passed in as the status argument, and any
     return options, including -errorinfo and -errorcode when  an  error  is  in
     progress.	This snapshot is returned as an opaque token of type Tcl_Interp-
     State.  The call to Tcl_SaveInterpState does not itself change the state of
     the interpreter.

     Tcl_RestoreInterpState  accepts a Tcl_InterpState token previously returned
     by Tcl_SaveInterpState and restores the state of the interp  to  the  state
     held  in  that snapshot.  The return value of Tcl_RestoreInterpState is the
     status value originally passed to Tcl_SaveInterpState when the snapshot to-
     ken was created.

     Tcl_DiscardInterpState is called to release a Tcl_InterpState token  previ-
     ously  returned  by Tcl_SaveInterpState when that snapshot is not to be re-
     stored to an interp.

     The Tcl_InterpState token returned by Tcl_SaveInterpState	must  eventually
     be  passed  to  either  Tcl_RestoreInterpState or Tcl_DiscardInterpState to
     avoid a memory leak.  Once the Tcl_InterpState token is passed  to  one  of
     them, the token is no longer valid and should not be used anymore.

KEYWORDS
     result, state, interp

Tcl				       8.1		  Tcl_SaveInterpState(3)
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