[Bug c++/67858] g++-5.1.1 warns about unused variable only when optimization flag is used

[crayzeewulf at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67858

--- Comment #1 from crayzeewulf <crayzeewulf at gmail dot com> ---
Here is the compiler command line and the warning:

$ g++ -Wall -std=c++11 -O3 -c bug_demo_code.cpp 
bug_demo_code.cpp:34:27: warning: ‘container’ defined but not used
[-Wunused-variable]
 const std::array<Item, 5> container {} ;