encountered compilation errors while building the ViSP library

[waliwali1111]

hello,I encountered compilation errors while building the ViSP library. The errors indicate that the std::mutex type is not declared, I have GCC 7.5.0, Ubuntu 18.04
/home/ros/visp-ws/visp/modules/core/include/visp3/core/vpImageConvert.h:155:32:
error: ‘std::mutex’ has not been declared
std::mutex *pointcloud_mutex = nullptr,
^~~
/home/ros/visp-ws/visp/modules/core/include/visp3/core/vpImageConvert.h:160:32:
error: ‘std::mutex’ has not been declared
std::mutex *pointcloud_mutex = nullptr,
Any help would be greatly appreciated