Problem:
When you try to compile your C/C++ project (typically a STM32 project):
C:/Users/User/MyProject/MyHeader.h:9:7: error: unknown type name 'size_t' 9 | const size_t MySize = 15; | ^~~~~~
Solution:
At the top of the file where this error occurs, add the following line:
#include <stddef.h>