Comment by drallison

Back when I was writing C compilers the Bourne Shell was my nemesis. The Bourne shell did exercise nearly every "feature" of the C language. Compiling and then running the shell was a great test case for an optimizing compiler and turned up many bugs. But, when the compiled code failed, winding back to the underlying C through the all of the macros and optimizations was exceptionally difficult. I still remember many a late night trying to figure out what happened. (Thanks Steve, for many fascinating hours of struggle.)