stat() takes a pointer to a struct where to write its output. This struct currently has 32bit values for time. If you updated stat() to write 64bit values into

stat() takes a pointer to a struct where to write its output. This struct currently has 32bit values for time. If you updated stat() to write 64bit values into a different struct, any existing program calling it with a pointer to an old struct would get garbage data (and a potential buffer overflow). Renaming the function also makes debugging easier - after statx() is in widespread use, stat() could be replaced with a placeholder that raises the SIGTRAP signal, and immediately detects epoch-unsafe programs still in use.