[Openmcl-devel] Raw-mode terminal weirdness redux

David Brown lisp at davidb.org
Tue Mar 27 10:05:47 PDT 2018

On Tue, Mar 27, 2018 at 09:32:54AM -0700, Ron Garret wrote:
>Found a reliable workaround!
> ...
>This version is broken.  If you comment out the line that says “This
>breaks it” it will start working properly.  Both working and
>non-working versions are 100% reliable.  Using a single RLET to
>allocate both termios structures also works.  It’s only when there is
>a call to tcgetattr in between the allocations that it breaks.  (Note
>that the “broken” version works in 1.8.  But for the fact that C code
>can reproduce this problem intermittently I would call this slam-dunk
>evidence that this is a bug in the CCL compiler, most likely in RLET.
>But since the C code does what it does, I’m not willing to go quite
>that far.)

The common thread in all of these, is that "raw" is only partially
initialized (cfmakeraw only initializes c_iflag).  Subtle changes in
stack positioning will make the initial values different, which
explains both the inconsistent behavior with the C program, and the
behavior of the lisp programs (and why it matters how you declare it).

You need to either tcgetattr again to fill in the 'raw' with the
current values, or copy the data from the 'normal' before calling
cfmakeraw on it.

My guess is that, with c_oflag being set to an uninitialized value, it
has flags set such that it generates no output.


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