Eli Zaretskii <eliz@gnu.org> writes:

> Thanks.  I think this needs an entry in NEWS.

Done.

> We don't put in Emacs sources compile-time conditionals that depend on
> the version of the OS on which Emacs is built: that would preclude the
> (very popular on Windows) practice of building Emacs on one system,
> and then using it on many others, possibly running other versions of
> the OS.

Thanks for this explanation and sorry that I didn't thought about this.
I changed it to use run-time dynamic linking.

> When the function is not available, you should assign ENOTSUP to
> errno, not EINVAL, to make the error message more accurate.

Done.

> Please test what this functionality does when PID specifies a child
> process of Emacs (which is tracked via the child_procs[] array), and
> also when it specifies the calling Emacs process itself.  If any of
> these use cases cause any kind of trouble, we may wish to disallow
> such usage, to prevent users from shooting themselves in the foot.

Sending SIGTRAP to a process -- whether it's an unrelated, child or the
calling Emacs process itself -- does not seem to have any effect as long
as no debugger is attached to the receiving process.  At least this is
what I observe on Windows 10.  Shall I test on other OS versions as
well?  If so, I would have to install say an Win XP first as I do not
have one available right now.  Unfortunately, on MSDN the remark on
DebugBreakProcess says it causes the receiving process to terminate in
most cases, see
https://msdn.microsoft.com/en-us/library/windows/desktop/ms679298(v=vs.85).aspx

But with all processes I tried, none of them was ever terminated.

Many thanks for your help.
Alain