@trusted assumptions about @safe code

[Arafel]

On 27/5/20 19:02, ag0aep6g wrote:
> I'm pretty sure that you agree with this: When we call C's strlen like 
> so: `strlen("foo\0".ptr)`, we can assume that the result will be 3, 
> because strlen is documented to behave that way.
> 

There's one big difference: in @safe there are bound checks by default, 
so even if you as the programmer assume that `strlen` will return the 
right value, the compiler is still inserting checks at every access:

```
@safe void safeFunc() {
     string foo = "foo\0");
     auto len = strlen(foo);
     auto bar = foo[0..len - 1]; // It'll be checked even in -release mode
}

@trusted void trustedFunc() {
     string foo = "foo\0");
     auto len = strlen(foo);
     auto bar = foo[0..len - 1];
}

```

So it's not that you needn't checks in @safe code, it's that they are 
added automatically.