eval_error.c: fix underflow

* eval_error.c (print_errinfo): get rid of negative string length.
  [ruby-core:86086] [Bug #14598]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62728 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

eval_error.c

@@ -129,15 +129,13 @@ print_errinfo(const VALUE eclass, const VALUE errat, const VALUE emesg, const VA
 	}
 	else {
 	    const char *tail = 0;
-	    long len = elen;
 
 	    if (emesg == Qundef && highlight) write_warn(str, bold);
 	    if (RSTRING_PTR(epath)[0] == '#')
 		epath = 0;
 	    if ((tail = memchr(einfo, '\n', elen)) != 0) {
-		len = tail - einfo;
+		write_warn2(str, einfo, tail - einfo);
 		tail++;		/* skip newline */
-		write_warn2(str, einfo, len);
 	    }
 	    else {
 		write_warn_str(str, emesg);
@@ -159,7 +157,7 @@ print_errinfo(const VALUE eclass, const VALUE errat, const VALUE emesg, const VA
 		    if (einfo[elen-1] == '\n') --elen;
 		    write_warn(str, bold);
 		}
-		write_warn2(str, tail, elen - len - 1);
+		if (tail < einfo+elen) write_warn2(str, tail, einfo+elen-tail);
 	    }
 	    if (tail ? (highlight || einfo[elen-1] != '\n') : !epath) {
 		if (highlight) write_warn(str, reset);

test/ruby/test_exception.rb

@@ -1254,5 +1254,13 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
 
     _, err2, status1 = EnvUtil.invoke_ruby(['-e', "#{test_method}; begin; foo; end"], '', true, true)
     assert_equal(err2, out1)
+
+    if $stderr.tty?
+      e = RuntimeError.new("a\n")
+      message = assert_nothing_raised(ArgumentError, proc {e.pretty_inspect}) do
+        e.full_message
+      end
+      assert_operator(message, :end_with?, "\n")
+    end
   end
 end