*** Error in `./BoxPtrUsage': double free or corruption (out): 0x00007ffc4f49ed10 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x777e5)[0x7f40da1757e5]
/lib/x86_64-linux-gnu/libc.so.6(+0x8037a)[0x7f40da17e37a]
/lib/x86_64-linux-gnu/libc.so.6(cfree+0x4c)[0x7f40da18253c]