Tcl_SaveInterpState(3tcl)

✨ Tcl_SaveInterpState — the save/restore-your-interp-state page ✨

okay so bestie, this is a page from the Tcl Library Procedures manual, and it's literally about taking a lil snapshot of your interpreter so you can bring it back later. no cap, this is a glow-up for your C code 💅

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💖 NAME 💖

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

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🌸 SYNOPSIS 🌸

#include <tcl.h>

Tcl_InterpState
Tcl_SaveInterpState(interp, status)

int
Tcl_RestoreInterpState(interp, state)

Tcl_DiscardInterpState(state)

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🎀 ARGUMENTS 🎀

• Tcl_Interp *interp (in) — the interpreter whose state we're saving. the main character, obviously.
• int status (in) — the return code value to save as part of the interpreter state.
• Tcl_InterpState state (in) — the saved state token that's gonna get restored or discarded.

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🦋 DESCRIPTION 🦋

so here's the vibe: these routines let a C procedure take a snapshot 📸 of the current state of an interpreter, so it can be restored after a call to Tcl_Eval or any other routine that messes with the interpreter state. like, save your progress before you go do something chaotic.

Tcl_SaveInterpState stores a snapshot of the interpreter state in an opaque token that it returns. that token value can then be passed back to either Tcl_RestoreInterpState or Tcl_DiscardInterpState, depending on whether the interp state is getting restored or not. and as long as you call one of those latter two routines, Tcl handles the memory management for you. we love a self-sufficient queen 🫶

Tcl_SaveInterpState takes a snapshot of those portions of interpreter state that make up the full result of script evaluation. this includes 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. that snapshot comes back as an opaque token of type Tcl_InterpState. and important: the call to Tcl_SaveInterpState does not itself change the state of the interpreter. it's just looking, not touching ✨

Tcl_RestoreInterpState accepts a Tcl_InterpState token that was 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 that was originally passed to Tcl_SaveInterpState when that snapshot token was created. it's giving time travel fr fr 🕰️

Tcl_DiscardInterpState is the one you call to release a Tcl_InterpState token previously returned by Tcl_SaveInterpState when that snapshot is not going to be restored to an interp. bye bestie, you served your purpose 👋

🚨 okay this part matters, no skipping: the Tcl_InterpState token returned by Tcl_SaveInterpState must eventually be passed to either Tcl_RestoreInterpState or Tcl_DiscardInterpState to avoid a memory leak. and once the Tcl_InterpState token is passed to one of them, that token is no longer valid and should not be used anymore. like, it's expired. don't text it back 💀

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⭐ KEYWORDS ⭐

result, state, interp

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and that's the whole page bestie, you ate 💅 this was Tcl, version 8.1, serving you the Tcl_SaveInterpState(3tcl) energy from the Tcl Library Procedures manual. go forth and snapshot responsibly 🎀✨