我遇到了一个使用Spirit Qi编写解析器的奇怪问题：我有一个错误导致-O优化导致崩溃，但没有优化。它在语法的构造函数内崩溃：
template <typename Iterator>
struct math_expression_grammar : qi::grammar<Iterator, std::string()>
{
qi::rule<Iterator, std::string()>
expression,
term,
factorial,
factor,
pexpression,
pfactor,
nfactor,
number;
math_expression_grammar():
math_expression_grammar::base_type(expression)
{
using namespace boost::spirit;
using namespace boost::spirit::ascii;
namespace sp = boost::spirit;
namespace ph = boost::phoenix;
auto sum = term[_val = sp::_1] >> lit('+') >> term[_val += sp::_1, _val += "+ "];
auto difference = term[_val = sp::_1] >> lit('-') >> term[_val += sp::_1, _val += "- "];
auto product = factor[_val = sp::_1] >> lit('*') >> factor[_val += sp::_1, _val += "* "];
auto dividend = factor[_val = sp::_1] >> lit('/') >> factor[_val += sp::_1, _val += "/ "];
expression = sum |
difference |
term;
term = product |
dividend |
factor;
pfactor = factorial.alias();
nfactor = (lit('-') >> pfactor)[_val = sp::_1 + "n "];
factor = nfactor | pfactor;
pexpression = lit('(') >> expression >> lit(')');
factorial = (pexpression | number)[_val = sp::_1] >> -lit('!')[_val += "! "];
number = sp::double_[_val = ph::bind(stringize<double>, sp::_1) + ' '];
}
};
我在Windows 64位上使用TDM GCC 4.8.2，在Arch Linux 64位上使用GCC 4.9.0进行测试;两者都有同样的问题。这是Valgrind跟踪的相关部分，打开了优化：
==15671== Use of uninitialised value of size 8
==15671== at 0x4040DA: void boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<char*, std::string>, std::string (), boost::spirit::unused_type, boost::spirit::unused_type, boost::spiri
t::unused_type>::define<mpl_::bool_<false>, boost::proto::exprns_::expr<boost::proto::tagns_::tag::bitwise_or, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tagns_:
:tag::bitwise_or, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tagns_::tag::shift_right, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tag
ns_::tag::shift_right, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tagns_::tag::subscript, boost::proto::argsns_::list2<boost::spirit::qi::rule<__gnu_cxx::__norma
l_iterator<char*, std::string>, std::string (), boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type>&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::
terminal, boost::proto::argsns_::term<boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval, boost::fusion::vector<boost::spirit::attribute<0>, boost::spirit::argument
<0>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > > cons
t&>, 0l> >, 2l> const&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::terminal_ex<boost::spirit::tag::lit, boost::fusion::vecto
r1<char> > >, 0l> const&>, 2l> const&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::subscript, boost::proto::argsns_::list2<boost::spirit::qi::rule<__gnu_cxx::__normal_iterator<ch
ar*, std::string>, std::string (), boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type>&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boo
st::proto::argsns_::term<boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::sequence_eval, boost::fusion::vector<boost::phoenix::composite<boost::phoenix::plus_assign_eval, boo
st::fusion::vector<boost::spirit::attribute<0>, boost::spirit::argument<0>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boo
st::fusion::void_, boost::fusion::void_, boost::fusion::void_> >, boost::phoenix::composite<boost::phoenix::plus_assign_eval, boost::fusion::vector<boost::spirit::attribute<0>, boost::phoen
ix::value<char const*>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusi
on::void_> >, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_>
> > const&>, 0l> >, 2l> const&>, 2l>&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::shift_right, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tagns_::ta
g::shift_right, boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tagns_::tag::subscript, boost::proto::argsns_::list2<boost::spirit::qi::rule<__gnu_cxx::__normal_itera
tor<char*, std::string>, std::string (), boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type>&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::termina
l, boost::proto::argsns_::term<boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval, boost::fusion::vector<boost::spirit::attribute<0>, boost::spirit::argument<0>, bo
ost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > > const&>, 0l
> >, 2l> const&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::terminal_ex<boost::spirit::tag::lit, boost::fusion::vector1<char
> > >, 0l> const&>, 2l> const&, boost::proto::exprns_::expr<boost::proto::tagns_::tag::subscript, boost::proto::argsns_::list2<boost::spirit::
==15671== by 0x404BD9: math_expression_grammar<__gnu_cxx::__normal_iterator<char*, std::string> >::math_expression_grammar() (in /home/collin/programming/parser/parser)
==15671== by 0x401E6A: main (in /home/collin/programming/parser/parser)
==15671== Uninitialised value was created by a stack allocation
==15671== at 0x404672: math_expression_grammar<__gnu_cxx::__normal_iterator<char*, std::string> >::math_expression_grammar() (in /home/collin/programming/parser/parser)
这里是关闭优化的整个日志：
==15686== Memcheck, a memory error detector
==15686== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==15686== Using Valgrind-3.9.0 and LibVEX; rerun with -h for copyright info
==15686== Command: ./parser
==15686==
==15686==
==15686== FILE DESCRIPTORS: 3 open at exit.
==15686== Open file descriptor 2: /dev/pts/5
==15686== <inherited from parent>
==15686==
==15686== Open file descriptor 1: /dev/pts/5
==15686== <inherited from parent>
==15686==
==15686== Open file descriptor 0: /dev/pts/5
==15686== <inherited from parent>
==15686==
==15686==
==15686== HEAP SUMMARY:
==15686== in use at exit: 0 bytes in 0 blocks
==15686== total heap usage: 14 allocs, 14 frees, 776 bytes allocated
==15686==
==15686== All heap blocks were freed -- no leaks are possible
==15686==
==15686== For counts of detected and suppressed errors, rerun with: -v
==15686== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 1 from 1)
两个测试之间的任何代码都没有变化。
我在实际调试问题时遇到了麻烦，因为错误只会导致-O优化或更高，但不幸的是-Og。我怀疑这可能是Boost.Spirit中的错误，但我也很不确定;我的代码中没有看到任何错误，但我可能会遗漏某些内容或使用Spirit错误。有经验的人可以指出我正确的方向吗？
以下是整个可编译代码：
#include <iostream>
#include <string>
#include <vector>
#include <stack>
#include <algorithm>
#include <utility>
#include <boost/mpl/vector.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/qi_real.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/bind.hpp>
#include <boost/ref.hpp>
namespace qi = boost::spirit::qi;
template <typename NumType, typename Iterator>
NumType inline parse_number(Iterator first, Iterator last)
{
using namespace std;
istringstream extractor(string(first, last));
NumType num;
extractor >> num;
return num;
}
template <typename NumType = double, typename Iterator>
NumType eval_rpn(Iterator head, Iterator last)
{
using namespace std;
const char tokens[] = {'+', '-', '*', '/', '^', 'n', ' '};
auto tokens_begin = begin(tokens), tokens_end = end(tokens);
stack<NumType> num_stack;
while(head != last)
{
auto next = find_first_of(head, last, tokens_begin, tokens_end);
if(head != next) num_stack.push(parse_number<NumType>(head, next));
if(next != last)
{
NumType temp;
switch(*next)
{
case '+':
temp = num_stack.top();
num_stack.pop();
num_stack.top() += temp;
break;
case '-':
temp = num_stack.top();
num_stack.pop();
num_stack.top() -= temp;
break;
case '*':
temp = num_stack.top();
num_stack.pop();
num_stack.top() *= temp;
break;
case '/':
temp = num_stack.top();
num_stack.pop();
num_stack.top() /= temp;
break;
case '^':
temp = num_stack.top();
num_stack.pop();
num_stack.top() = pow(num_stack.top(), temp);
break;
case 'n':
num_stack.top() = -num_stack.top();
break;
default:
break; // Do nothing
}
head = next+1;
}
else head = last;
}
return num_stack.top();
}
template <typename T>
std::string stringize(T x)
{
return std::to_string(x);
}
template <typename Iterator>
struct math_expression_grammar : qi::grammar<Iterator, std::string()>
{
qi::rule<Iterator, std::string()>
expression,
term,
factorial,
factor,
pexpression,
pfactor,
nfactor,
number;
math_expression_grammar():
math_expression_grammar::base_type(expression)
{
using namespace boost::spirit;
using namespace boost::spirit::ascii;
namespace sp = boost::spirit;
namespace ph = boost::phoenix;
auto sum = term[_val = sp::_1] >> lit('+') >> term[_val += sp::_1, _val += "+ "];
auto difference = term[_val = sp::_1] >> lit('-') >> term[_val += sp::_1, _val += "- "];
auto product = factor[_val = sp::_1] >> lit('*') >> factor[_val += sp::_1, _val += "* "];
auto dividend = factor[_val = sp::_1] >> lit('/') >> factor[_val += sp::_1, _val += "/ "];
expression = sum |
difference |
term;
term = product |
dividend |
factor;
pfactor = factorial.alias();
nfactor = (lit('-') >> pfactor)[_val = sp::_1 + "n "];
factor = nfactor | pfactor;
pexpression = lit('(') >> expression >> lit(')');
factorial = (pexpression | number)[_val = sp::_1] >> -lit('!')[_val += "! "];
number = sp::double_[_val = ph::bind(stringize<double>, sp::_1) + ' '];
}
};
int main()
{
using namespace std;
math_expression_grammar<string::iterator> g;
string input;
getline(cin, input);
while(input.size())
{
auto first = input.begin(), last = input.end();
cout << input << endl;
string result;
if(!boost::spirit::qi::parse(first, last, g, result))
{
cout << "Error at " << last - first << ":\n\t" << *first << endl;
}
else
{
cout << result << endl;
cout << eval_rpn(result.begin(), result.end()) << endl;
}
getline(cin, input);
}
}