Tcl_SaveInterpState(3)

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
Interpreter for which state should be saved. Return code value to save as part of interpreter state. Saved state token to be restored or discarded.

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 latter 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 interpreter 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_InterpState. 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 token was created.

Tcl_DiscardInterpState is called to release a Tcl_InterpState token previously returned by Tcl_SaveInterpState when that snapshot is not to be restored 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 Once the Tcl_InterpState token is passed to one of them, the token is no longer valid and should not be used anymore.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