On Unix-like operating systems stdio.h is usually line-buffered. As
putStr uses fputs(3) from stdio.h internally, output will be written to
standard out after a newline character is written to the buffer. Since
the prompt does not contain a newline, it will only be written to
standard output after the user presses return. I encountered this issue
on Alpine Linux which uses musl libc (instead of glibc). However, I
believe this issue is likely also reproducible with glibc. This commit
fixes this issue by flushing standard output after writing the prompt to
it. Surprisingly, `src/Idris/IDEMode/REPL.idr` already does this
correctly, `src/Idris/REPL.idr` does not though.
This involves new primitives GCPtr and GCAnyPtr which are pointer types
that have finalisers attached. The finalisers are run when the
associated pointer goes out of scope.
In the test, I am assuming that the GC will only be called once, right
at the end. Otherwise, the output isn't guaranteed to be deterministic!
Let's see how this assumption holds...
This is currently Chez only. I think it'll be easy enough to add to
the Racket and Gambit back ends too.
