Tcl_CallWhenDeleted(3)

💖 Tcl_CallWhenDeleted — bestie edition 💖

okay so this is the Tcl Library Procedures page for Tcl_CallWhenDeleted and Tcl_DontCallWhenDeleted, and honestly? it's giving "i want a lil heads-up before my interpreter ✨perishes✨". sit with me, this one's short and sweet. 🎀

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✨ NAME ✨

Tcl_CallWhenDeleted, Tcl_DontCallWhenDeleted — arrange for a callback for when the interpreter is deleted 🫶

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🌸 SYNOPSIS 🌸

#include <tcl.h>

Tcl_CallWhenDeleted(interp, proc, clientData)

Tcl_DontCallWhenDeleted(interp, proc, clientData)

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🦋 ARGUMENTS 🦋

• Tcl_Interp *interp (in) — the interpreter you're associating this callback with. it's her interpreter. 💅
• Tcl_InterpDeleteProc *proc (in) — the procedure to call when interp gets deleted.
• void *clientData (in) — an arbitrary one-word value that gets passed to proc. one word. that's it. no more, no less. 💀

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🌈 DESCRIPTION 🌈

Tcl_CallWhenDeleted arranges for proc to be called by Tcl_DeleteInterp if/when interp is deleted at some future time. if/when — like, not right now, but eventually, whenever that moment comes. ⏳

proc will be invoked just before the interpreter is deleted, but — and this is the important part, bestie — the interpreter will still be valid at the time of the call. so you're saying goodbye while she's still standing. 😭 iconic behaviour.

proc should have arguments and result that match the type Tcl_InterpDeleteProc:

typedef void Tcl_InterpDeleteProc(
        void *clientData,
        Tcl_Interp *interp);

the clientData and interp parameters are copies of the clientData and interp arguments you gave to Tcl_CallWhenDeleted. typically, clientData points to an application-specific data structure that proc uses to perform cleanup when an interpreter is about to go away. the cleanup era. 🧹✨

and proc does not return a value. it returns void. no notes, no receipts, no little gift back. 💜

Tcl_DontCallWhenDeleted cancels a previous call to Tcl_CallWhenDeleted with the same arguments, so that proc will not be called after all when interp is deleted. it's the "jk bestie, nevermind" of functions. 🙈

if there is no deletion callback that matches interp, proc, and clientData, then the call to Tcl_DontCallWhenDeleted has no effect. like, literally nothing happens. vibe check: failed, but gently. 🫶

⚠️ heads up bestie ⚠️ note that if the callback is being used to delete a resource that must be released on exit, Tcl_CreateExitHandler should be used to ensure that a callback is received even if the application terminates without deleting the interpreter. do NOT skip this. the interpreter might dip without warning and your cleanup would be left on read. 💀

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👑 SEE ALSO 👑

• Tcl_CreateExitHandler(3)
• Tcl_CreateThreadExitHandler(3)

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🎀 KEYWORDS 🎀

callback, cleanup, delete, interpreter

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and that's the whole page, bestie, no cap. this one's from the Tcl 7.0 era — yes, 7.0, she's vintage, she's a classic, she ate and left no crumbs. 💅✨ mwah, go clean up your interpreters responsibly. 🦋🌸