Re: [boost] [gil] gcc fail with simple code

Subject: Re: [boost] [gil] gcc fail with simple code
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2018-03-28 17:52:02

On 03/28/18 20:30, Christian Henning via Boost wrote:
> Hi all,
> 
> we are, at the boost::gil corner, investigating a runtime failure when
> compiling with gcc 5.4. When running in release configuration the following
> code fails:
> 
> #include <iostream>
> #include <boost/gil/gil_all.hpp>
> 
> using namespace boost::gil;
> using namespace std;
> 
> void error_if(bool condition) {
>      if (condition)
>          throw std::exception();
> }
> 
> bits32s c32s_min = channel_traits<bits32s>::min_value();
> bits32s c32s_max = channel_traits<bits32s>::max_value();
> 
> // For channel values simply initialize the value directly
> template <typename ChannelValue>
> struct value_core {
>      typedef ChannelValue channel_t;
>      channel_t _min_v, _max_v;
> 
>      value_core() : _min_v(channel_traits<ChannelValue>::min_value()),
> _max_v(channel_traits<ChannelValue>::max_value())
>      {}
> };
> 
> int main(int argc, char *argv[])
> {
>      value_core<bits32s> a;
> 
>      bits32s v_min, v_max;
> 
>      v_min = channel_convert<bits32s>(c32s_min);
>      v_max = channel_convert<bits32s>(c32s_max);
> 
>      //std::cout << v_min << std::endl;
>      // std::cout << this->_min_v << std::endl;
>      //std::cout << v_max << std::endl;
>      // std::cout << this->_max_v << std::endl;
> 
>      error_if(v_min != a._min_v || v_max != a._max_v);
> }
> 
> The interesting thing is that everything works with the cout's enabled.
> 
> Has anyone ever dealt with a similar issue?

Most likely, you have a signed integer overflow somewhere. The code 
crashes on gcc 7.2 with -O3 but doesn't crash with -O0 or with -O3 -fwrapv.