https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77550
Bug ID: 77550
Summary: std::deque with -O3 has infinite std::distance
Product: gcc
Version: 6.2.0
Status: UNCONFIRMED
Severity: critical
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dan.cooke89 at gmail dot com
Target Milestone: ---
The following program, compiled with -O3, never returns:
#include <string>
#include <deque>
#include <iterator>
#include <iostream>
#include <boost/iterator/filter_iterator.hpp>
struct Foo
{
std::string bar, s = "";
char a = '\0';
};
int main()
{
const std::deque<Foo> foos(14, {""});
const std::string test {};
const auto p = [test] (const auto& foo) { return foo.bar == test; };
using boost::make_filter_iterator;
const auto begin = make_filter_iterator(p, std::cbegin(foos),
std::cend(foos));
const auto end = make_filter_iterator(p, std::cend(foos),
std::cend(foos));
std::cout << std::distance(begin, end) << std::endl;
}
Observations:
- GCC with optimisations -O2 or less returns as expected.
- Clang (3.8) returns the correct answer with any optimisation level.
- Changing std::deque to std::vector or std::list results in expected
behaviour.
- The 14 is critical; anything less and the problem disappears.
- The sizeof(Foo) is important; removing s or a makes the problem go away.
- Capturing test by reference, or just comparing to a constant expression
(e.g. foo.bar == " ") results in normal behaviour.
- There are no compiler warnings (with -Wall -Wextra -pedantic).
- Valgrind reports no errors.
- Use fsanitize=undefined and the problem goes away.
From: http://stackoverflow.com/q/39424753/2970186
