What is safe and unsafe really?
“You are allowed to do this, but you had better know what you are doing.”
- A Rustacean
When we talk about safety in programming languages, it is a property that spans different levels. A language can be memory-safe, type-safe, or it can be concurrent-safe. Memory safety means that a program doesn't write to a forbidden memory address and it doesn't access invalid memory. Type safety means that a program doesn't allow you to assign a number to a string variable and that this check happens at compile time, while concurrent-safe means that the program does not lead to race conditions when multiple threads are executing and modifying a shared state. If a language provides all of these levels of safety by itself, then it is said to be safe. To put it more generally, a program is deemed safe if, in all possible executions of the program and for all possible inputs, it gives correct outputs, does not lead to crashes, and does not clobber or corrupt its internal or...
