Turns out I have had a script ~/bin/CC in my path since circa 1980. cc plus some pleasant defaults. It has worked from UNIX v6 through v7, Eunice, BSD 4.1, 4.2, 4.3, SVr4, Xenix, Gould UTX, Linux, cygwin... and it failed for the first time on MacOS, infinite recursion.
I wondered if HFS+'s case insensitivity could be exploited for a security hole. Googling reveals that the problem has already been encountered article.gmane.org/gmane.linux.kernel/1853266itworld.com/article/2868393/… January 2015 Although fixed in Git, this is an exploit waiting to happen, for Mac users who have ever installed software from some other UNIX-like case-sensitive system. For that matter, it is probably a potential security hole for code ported from case sensitive iOS to Mac OS X.