On Tue, Jun 27, 2017, at 09:54, Richard Tobin wrote: Hmm. It seems that the truth is a little bit more convoluted than that, but it was a good starting point. The equivalent functionality in V7/usr/src/cmd/standalone uses "libsa" (in addition to, rather than instead of, libc) and srt0.o, and was used with a "cc+ld-stand" script which read as follows: cc -c -O -DSTANDALONE ../$1.c ld -s -o $1 srt0.o $1.o -lsa -lc rm $1.o The equivalent manpage in System III mentions crt20.o instead. System III scc invokes cc with "-2x" (System V uses -Z2). So, mystery solved, I guess, except for why it appears in the V6 (and V5, and V2) cc with no trace of the needed libraries, and V7 with the libraries having a different structure. My guess is that the V7 library structure was a post-V6 change that didn't make it into USG Unix. My assumption is that it's dead code at that point. The v7 cc+ld-stand script doesn't seem to have been suitable for multi-file programs, either - no other version has this script, either (Ultrix and BSD seem to both have standalone systems derived from it, but both just have the relevant cc and ld commands in their makefiles) So, my theorized timeline: This began as an internal tool in V2*. USG Unix and V7 diverged, and V7 effectively abandoned the use of a magic flag and hardcoded library names in "cc" (but for some reason retained the actual associated functionality in "cc" itself, where it survived into Ultrix 3.1 and 3BSD but not 4BSD). Ultrix and BSD took V7's version of the functionality. *specifically, it appears in V2/cmd/cc.c which comes from s1-bits. It does not appear in V2/c/ncc.c which comes from last1120c.