It still doesn't, this is a compiler specific language extension.
replyYou won't find anything on ISO/IEC 9899:2024 about tail calls, like it happens on Scheme.
https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf
Section 3.5 of R7RS.
A formal technical specification (TS) extension is already being drafted: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3582.pdf That's a step up from the usual proposals. I'm not sure what criteria is used to decide whether to first create a TS vs just incorporating a change into the working draft of the next standard.[1] _Defer also seems to be taking the TS route.[2]
reply1. https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3886.pdf
2. https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3928.pdf
There's some discussion of how C29 defer ended up in a TS at https://thephd.dev/c2y-the-defer-technical-specification-its... .
replyWell, even if that lands on the official standard, that means C29 as probable release year for C2y, plus adoption of the exact form across compilers to be able to rely on it being available.
replyPlus the fact that an implementation that recognizes the new syntax and produces an error whenever it encounters it will be conforming.
replyOn such an implementation, the feature is available but useless.
Woops, I meant to write tail call optimization not tail calls. Shouldn't have used the term interchangeably. Yeah I'm aware that C doesn't have proper tail calls. Thanks for the correction though.
replyI think Anton is wrong. Since C89 and before C23 calling an `int f();` function with arguments not matching the definition's actuals is UB. In C23 `int f();` became the same as `int f(void);`, so calling that function with any arguments is a compile-time error.
replyFor variadic functions, if you use `va_start()`/`va_arg()`/`va_end()` to consume all the arguments, and leave no `va_list` alive, then the compiler can correctly generate a tail call from such functions.