Hi,
I have a program which produces different results based on the compiler options. The program uses a boost::any_range containing a transformed range where the transformation function just returns a new object of a simple struct:
#include <vector>
#include
#include
#include
#include <iostream>
template void ASSERT_EQ(T1 x,T2 y) {assert(x == y);};
struct SourceEvent
{
std::uint32_t event;
void* ptr;
};
int main()
{
using boost::adaptors::transformed;
using R = boost::any_range;
std::vectorstd::int32_t v(100);
R r = v | transformed( [](auto const&) {return SourceEvent{0u, nullptr};} );
auto t = v | transformed( [](auto const&) {return SourceEvent{0u, nullptr};} );
ASSERT_EQ( 100u, boost::size(r) );
ASSERT_EQ( 100u, boost::size(t) );
for (auto const& i: t)
{
ASSERT_EQ(0u, i.event );
ASSERT_EQ(nullptr, i.ptr);
}
for (auto const& i: r)
{
ASSERT_EQ(0u, i.event );
ASSERT_EQ(nullptr, i.ptr);
}
std::cout << "OK" << std::endl;
return 0;
}
When compiled without optimization, it just prints ok. The same source compiled with optimizations asserts, and prints some interesting warnings:
In file included from /usr/local/boost-1.60.0/include/boost/range/detail/any_iterator.hpp:22:0,
from /usr/local/boost-1.60.0/include/boost/range/any_range.hpp:17,
from prog.cc:3:
/usr/local/boost-1.60.0/include/boost/range/detail/any_iterator_wrapper.hpp: In member function 'boost::range_detail::any_forward_iterator_wrapper::reference boost::range_detail::any_forward_iterator_wrapper::dereference() const [with WrappedIterator = boost::iterators::transform_iterator, SourceEvent>, __gnu_cxx::__normal_iterator, boost::iterators::use_default, boost::iterators::use_default>; Reference = SourceEvent; Buffer = boost::any_iterator_buffer<64ul>; boost::range_detail::any_forward_iterator_wrapper::reference = SourceEvent&]':
/usr/local/boost-1.60.0/include/boost/range/detail/any_iterator_wrapper.hpp:302:57: warning: function may return address of local variable [-Wreturn-local-addr]
return dereference_cast<reference>(*m_it);
^
/usr/local/boost-1.60.0/include/boost/range/detail/any_iterator_wrapper.hpp:302:52: note: declared here
return dereference_cast<reference>(*m_it);
^
prog.exe: prog.cc:7: void ASSERT_EQ(T1, T2) [with T1 = unsigned int; T2 = unsigned int]: Assertion `x == y' failed.
Aborted
The example is compiled with gcc 5.2 and boost 1.60 (http://melpon.org/wandbox/permlink/QF1qyw5bWHKwyKJ8). Is there an error in my code? I would guess that transforming a range into a range of new objects of another type is quite common, so it should work. I am also curious why the warning is only emitted when compiling with optimizations.
Best wishes,
Jens
--
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