Adds --abort-on-int cmdline flag to yices executable.

We use the yices executable (and not the yices_smt2 executable) as a
sub-process solver from our primary application.  Our application
expects normal cleanup to the foreground process group to occur on
Ctrl-C / SIGINT, but currently it will exit and leave the yices
process running in the background because yices does not exit on this
event.

This small patch adds the cmdline flag that we can use from our
application to run yices in a mode that will exit on these events.
The default is the current behavior so this change should be fully
backward-compatible.

src/frontend/yices/yices_reval.c

@@ -128,6 +128,8 @@
  *   and we don't exit on error.
  * - print_success: if this flag is true, we print "ok" after every
  *   command that would otherwise print nothing.
+ * - abort_on_int: if true then exit when SIGINT is received instead
+ *   of returning to input processing (the default).
  * - verbosity: verbosity level
  * - done: set to true when exit is called, or if there's an error and
  *   interactive is false (i.e., we exit on the first error unless we're
@@ -145,6 +147,10 @@
  *   by default, these are NULL
  * - mcsat_requested: option --mscat (this forces use of the MC-SAT solver
  *   for logic where MC-SAT is not the default).
+ * - print-success: print success for commands that would otherwise
+ *   complete silently
+ * - abort-on-int: abort execution on SIGINT instead of returning to
+ *   input processing
  *
  * CONTEXT CONFIGURATION
  * - logic_code = code for the logic_name (default is SMT_UNKNNOW)
@@ -164,6 +170,7 @@ static uint32_t include_depth;
 static bool interactive;
 static bool done;
 static bool print_success;
+static bool abort_on_int;
 static int32_t verbosity;
 static tracer_t *tracer;
 
@@ -269,6 +276,7 @@ enum {
   version_flag,
   help_flag,
   print_success_flag,
+  abort_on_int_flag,
   verbosity_option,
 };
 
@@ -282,6 +290,7 @@ static option_desc_t options[NUM_OPTIONS] = {
   { "version", 'V', FLAG_OPTION, version_flag },
   { "help", 'h', FLAG_OPTION, help_flag },
   { "print-success", '\0', FLAG_OPTION, print_success_flag },
+  { "abort-on-int", '\0', FLAG_OPTION, abort_on_int_flag },
   { "verbosity", 'v', MANDATORY_INT, verbosity_option },
 };
 
@@ -412,6 +421,7 @@ static void process_command_line(int argc, char *argv[]) {
   mcsat_requested = false;
   verbosity = 0;
   print_success = false;
+  abort_on_int = false;
   tracer = NULL;
   logic_code = SMT_UNKNOWN;
   arith_code = ARITH_SIMPLEX;
@@ -495,6 +505,10 @@ static void process_command_line(int argc, char *argv[]) {
 	print_success = true;
 	break;
 
+      case abort_on_int_flag:
+        abort_on_int = true;
+        break;
+
       case verbosity_option:
 	v = elem.i_value;
 	if (v < 0) {
@@ -792,7 +806,7 @@ static void default_handler(int signum) {
  * Initialize the signal handlers
  */
 static void init_handlers(void) {
-  signal(SIGINT, sigint_handler);
+  signal(SIGINT, abort_on_int ? default_handler : sigint_handler);
   signal(SIGABRT, default_handler);
 #ifndef MINGW
   signal(SIGXCPU, default_handler);