Spirit parse_nan() may dereference end iterator

[michael.douglas.schmidt@…]

The function parse_nan(first, last) will dereference the end iterator when parsing the string "nan", which may lead to undefined behavior.

File: boost/spirit/home/qi/numeric/real_policies.hpp
Line: 119

This occurs for instance using the following parser:

std::string s = "nan";
auto s_begin = s.begin();
auto s_end   = s.end();
double out;
qi::phrase_parse(s_begin, s_end, qi::double_, ascii::space, out);

The problem occurs in parse_nan():

117: if (detail::string_parse("nan", "NAN", first, last, unused))
118: {
119:     if (*first == '(')

Line 119 should check if first == last first since detail::string_parse() may increment first.

[cbielow]

I just stumpled over this bug as well (boost 1.54)

It is fixed in Boost 1.60 (or earlier?), i.e.,

// nan[(...)] ?
if (detail::string_parse("nan", "NAN", first, last, unused))
{
  if (first != last && *first == '(')
  {

So I guess ticket can be closed?