Make error: ‘bit_cast’ is not a member of ‘std’; did you mean ‘bad_cast’?

[zhangyingjie7]

Hi all,
I follow the tutorial to compile MOTION, but when I run "make", error occurs

MOTION/src/motioncore/utility/helpers.h:516:15: error: ‘bit_cast’ is not a member of ‘std’; did you mean ‘bad_cast’?
  516 |   return std::bit_cast<U>(input);
      |               ^~~~~~~~
      |               bad_cast
MOTION/src/motioncore/utility/helpers.h:516:25: error: expected primary-expression before ‘>’ token
  516 |   return std::bit_cast<U>(input);
      |                         ^

Could you please help me with this?

Packages version in my computer

gcc version 10.5.0 (Ubuntu 10.5.0-1ubuntu1~20.04)
boost version 1.76
openssl version 1.1.1f

[robinhundt]

Hi, as noted in the readme, you need a compiler with support for C++20. It seems the given recommendation of >=10 is to low, as version 10 does not support all parts of C++20 that are used by MOTION. Notably, std::bit_cast is implemented in libstdc++ version 11.1 (see https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html).

I recommend you upgrade your compiler to the newest version. GCC13 came with some breaking changes as well, but these should be fixed on the main branch by now.