Remove several race conditions with signal handler (bug #61370). This patch removes several race conditions between the interpreter and the Ctrl-C signal handler, as described in more detail in bug #61370. * libinterp/corefcn/sighandlers.h: Make can_interrupt atomic. * libinterp/corefcn/sighandlers.cc: Make can_interrupt, signals_caught atomic, use atomic value read for signals_caught, octave_interrupt_state, change 1 to true. * liboctave/util/quit.h: Move octave_interrupt_state and octave_signal_caught to C++ only code, rewrite octave_quit() function, rewrite OCTAVE_QUIT macro to use octave_quit_c() function. * liboctave/util/quit.cc: Make octave_interrupt_state and octave_signal_caught atomic, add new wrapper function octave_quit_c(). * libinterp/corefcn/interpreter.h: Make octave_initialized atomic. * libinterp/corefcn/interpreter.cc: Make octave_initialized atomic, change 0 to false. * liboctave/util/action-container.h: New namespace "util", make m_val atomic. * liboctave/util/oct-atomic.c: Reorder preprocessor if-elif-else ladder. * liboctave/util/cmd-edit.cc: Change 0 to false.

--- a/libinterp/corefcn/sighandlers.h	Sat Dec 03 13:55:14 2022 +0100
+++ b/libinterp/corefcn/sighandlers.h	Sat Dec 03 10:36:59 2022 -0500
@@ -36,6 +36,8 @@
 #if ! defined (octave_sighandlers_h)
 #define octave_sighandlers_h 1
 
+#include <atomic>
+
 #include "octave-config.h"
 
 #include "child-list.h"
@@ -56,7 +58,7 @@
 extern int pipe_handler_error_count;
 
 // TRUE means we can be interrupted.
-extern OCTINTERP_API bool can_interrupt;
+extern OCTINTERP_API std::atomic<bool> can_interrupt;
 
 extern OCTINTERP_API sig_handler *
 set_signal_handler (int sig, sig_handler *h,