45083: Add signal protection to execarith().

Otherwise we could get re-entrancy in memory functions when
setting variables.

ChangeLog

@@ -1,3 +1,8 @@
+2019-12-18  Peter Stephenson  <p.stephenson@samsung.com>
+
+	* 45083: Src/exec.c: execarith() needs signal protection as
+	it sets variables.
+
 2019-12-18  Daniel Shahaf  <danielsh@apache.org>
 
 	* 45076: Src/loop.c: internal: Simplify handling of

Src/exec.c

@@ -5101,6 +5101,7 @@ execarith(Estate state, UNUSED(int do_exec))
     mnumber val = zero_mnumber;
     int htok = 0;
 
+    queue_signals();
     if (isset(XTRACE)) {
 	printprompt4();
 	fprintf(xtrerr, "((");
@@ -5120,6 +5121,8 @@ execarith(Estate state, UNUSED(int do_exec))
 	fprintf(xtrerr, " ))\n");
 	fflush(xtrerr);
     }
+    unqueue_signals();
+
     if (errflag) {
 	errflag &= ~ERRFLAG_ERROR;
 	return 2;