It’s also a shell script. It’s a shell script written purely in POSIX–compatible sh, that is generated by the worst M4 script ever written. The information whic

It’s also a shell script. It’s a shell script written purely in POSIX–compatible sh, that is generated by the worst M4 script ever written. The information which will be printed to stdout, to the log files, to the cache files, to the status file, and so on all needs to be buffered until the end of any asynchronous task, then written atomically so that it can be understood and will work consistently. That’s synchronizing writes to six or seven different file descriptors, just so that everything comes out in a comprehensible order. I bet you're already thinking about how to implement it though. And it does quite a lot more than just probe the compiler. And finally, it doesn’t support concurrent execution because nobody who was tried to write it has returned. Usually it starts with confident estimates and preparations, followed by departure and sporadic reports. Gradually the reports dwindle in frequency and comprehensibility, until eventually nothing more is heard.