Comment by pjmlp

It still doesn't, this is a compiler specific language extension.

You 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.

https://standards.scheme.org/official/r7rs.pdf