Hi: Tried Jonny Grant's example g++ -O3 --std=c++23 -Wall -c repro_jg01.cc With the mainline build, the code compiles without any error. Environment - Linux 6.1.0-3-amd64 x86_64 GNU/Linux - Debian GLIBC 2.36-8) 2.36 - gcc version 13.0.1 20230215 (experimental) (GCC) Curious to know, what changed in the mainline code ? Anyone knows the commit hash ? warm regards Saifi.