From: Alexei Sheplyakov <varg@theor.jinr.ru>
Date: Sat, 13 Sep 2008 23:26:33 +0000 (+0400)
Subject: parser: add necessary checks to operator() to stop accepting nonsense.
X-Git-Tag: release_1-5-0~59^2~6
X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=commitdiff_plain;h=1261c54df6548cf558405a118b2134805f63376d;ds=inline

parser: add necessary checks to operator() to stop accepting nonsense.

Since the parser is recursive parse_* methods (in particular,
parse_binop_rhs()) does NOT check if the last unparsed token is valid.
Thus parse_expression() stops if it encounters an unknown token. That's
why parser::operator() needs to make sure nothing is left in the input
stream.
---

diff --git a/check/parser_bugs.cpp b/check/parser_bugs.cpp
index a83f668a..af32c5ef 100644
--- a/check/parser_bugs.cpp
+++ b/check/parser_bugs.cpp
@@ -58,6 +58,22 @@ static int check3(std::ostream& err_str)
 	return 0;
 }
 
+/// parser happily accepted various junk like 'x^2()+1'
+static int check4(std::ostream& err_str)
+{
+	const std::string junk("x^2()+1");
+	parser reader;
+	ex e;
+	try {
+		e = reader(junk);
+		err_str << "parser accepts junk: \"" << junk << "\"" << std::endl;
+		return 1;
+	} catch (parse_error& err) {
+		// Ok, parser rejects the nonsense.
+		return 0;
+	}
+}
+
 int main(int argc, char** argv)
 {
 	std::cout << "checking for parser bugs. " << std::flush;
@@ -66,6 +82,7 @@ int main(int argc, char** argv)
 	errors += check1(err_str);
 	errors += check2(err_str);
 	errors += check3(err_str);
+	errors += check4(err_str);
 	if (errors) {
 		std::cout << "Yes, unfortunately:" << std::endl;
 		std::cout << err_str.str();
diff --git a/ginac/parser/parser.cpp b/ginac/parser/parser.cpp
index 6cac523c..6411ba14 100644
--- a/ginac/parser/parser.cpp
+++ b/ginac/parser/parser.cpp
@@ -138,6 +138,13 @@ ex parser::operator()(std::istream& input)
 	scanner->switch_input(&input);
 	get_next_tok();
 	ex ret = parse_expression();
+	// parse_expression() stops if it encounters an unknown token.
+	// This is not a bug: since the parser is recursive checking
+	// whether the next token is valid is responsibility of the caller.
+	// Hence make sure nothing is left in the stream:
+	if (token != lexer::token_type::eof)
+		Parse_error("expected EOF");
+
 	return ret;
 }