Severe regressions in context of keyboard macros

[Christoph Arenz <tiga.arenz@web.de>]

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I think I have found two regressions that were introduced some time ago
by commit 30a6b1f81412044a, affecting keyboard macros. One is severely
affecting calc to the point of leading to completely wrong results -- if
not stopped by an error first. The other is affecting how dribble writes
out recorded keys.

Calc:
I stumbled across the following bug using calc -- see also
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=37057:
90 <RET> S <f3> I S <f4>
This calculates the sine and inverse sine of 90 -- with a result of 90.
It also records "IS" as a keyboard macro.
Now, let's use the macro to complete the same calculation:
90 <RET> S <f4>
This worked until emacs-24.5 but is broken since emacs-25.1 where "ISS"
is recorded as a keyboard macro -- now leading to a result of 1.

It seems all macros that involve calc's prefix keys (e.g. "I" or "H")
have the following key recorded twice in last-kbd-macro. E.g. "IHP" is
recorded as "IHHPP", pushing GAMMA and PI on the stack instead of one
constant, namely PHI.

Hopefully, the calculation breaks due to an error -- otherwise, you get
nonsense results which might be hard to debug, if noticed at all.


Dribble:
According to the documentation in open-dribble-file, this starts
'writing all keyboard characters to a dribble file'.
However, the keys being recorded changed with commit 30a6b1f81412044a
when a keyboard macro is involved.

Prior, the key "<f4>" was recorded when a macro was replayed. With the
patch, the recording contains "<f4>" and additionally all characters
that were replayed by the macro. This gets ugly quickly, e.g. when <f3>
was used in the macro to insert a counter.


I am not suggesting that reverting commit 30a6b1f81412044a is the final
and right solution, but it does resolve the two issues in calc and
dribble in emacs-26.3. I stumbled across the mail thread
https://lists.gnu.org/archive/html/emacs-devel/2015-08/msg00193.html
where there were some doubts whether the quick fix could break something
else.

Keyboard.c seems highly complex and magic to me. I first thought that
sit-for in subr.el might have something to do with it as it has fixme
comments mentioning unread-command-events. Just a wild guess...



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