Tcl_AllowExceptions(3tcl)

✨ Tcl_AllowExceptions ✨

okay so bestie, welcome to the Tcl_AllowExceptions(3tcl) page — it's a Tcl library procedure and it's literally about letting your script throw whatever completion code it wants instead of Tcl being like "no 💀, that's an error now."

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🌸 SYNOPSIS 🌸

#include <tcl.h>

Tcl_AllowExceptions(interp)

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🎀 ARGUMENTS 🎀

• Tcl_Interp *interp (in) — the interpreter where the script is gonna get evaluated, periodt.

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💖 DESCRIPTION 💖

So here's the vibe. When a script gets evaluated at top-level — meaning like, no other scripts are pending evaluation when you invoke it — and that script finishes with a completion code that is not TCL_OK, not TCL_ERROR, and not TCL_RETURN… Tcl's default behaviour is to be a little dramatic and convert that whole thing into a TCL_ERROR return, with an appropriate message attached. Not it. 🙈

The specific Tcl script evaluation procedures that do this are:

• Tcl_EvalObjEx
• Tcl_EvalObjv
• Tcl_Eval
• Tcl_EvalEx
• Tcl_GlobalEval
• Tcl_GlobalEvalObj
• Tcl_VarEval

<bubble>BUT</bubble> — and this is the iconic part — if you call Tcl_AllowExceptions immediately before calling one of those procedures, then arbitrary completion codes are permitted from the script, and they get returned without modification. No conversion, no meddling, no notes. 💅

This is highkey useful when the caller can actually deal with exceptions like TCL_BREAK or TCL_CONTINUE in a meaningful way — like, the caller knows what to do with them, so let them cook. 🔥

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🔑 KEYWORDS 🔑

continue, break, exception, interpreter

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okay that's the whole page, slay 💜 — this was Tcl 7.4, dated 7.4, filed under Tcl_AllowExceptions(3tcl), and yes the footer says the same thing as the header because that's just how manpages do. no cap. 🦋