4 ms·
They're not talking about that - you could do: struct vec_int vec = VEC_INT_EMPTY; vec_int_push(&vec,1); vec_int_push(&vec,2); vec_int_push(&vec,3); e
by a1369209993 6y ago
They're not talking about that - you could do:
struct vec_int vec = VEC_INT_EMPTY;
vec_int_push(&vec,1);
vec_int_push(&vec,2);
vec_int_push(&vec,3);
even in C. They're talking about things like:
Foo foo; // Foo::Foo allocates
z = x + y; // operator+ allocates
w = x; // operator= allocates
foo += *bar; // operator* allocates
Rust can do most of those things, but it's not encouraged and significantly less pervasive, especially in the kind of code you'd want to use in a kernel in the first place.
- pjmlp 6y agoSo it can, case closed. Being encouraged or not, doesn't control the hands of those typing the code.
- unionpivo 6y ago> So it can, case closed. Being encouraged or not, doesn't control the hands of those typing the code. Sure in theory. But in practice most consider such a behavior a code small or straight bug an d fix it. So there is a difference in practice.
- pjmlp 6y agoIn theory every expert level C developer writes correct code, in practice errors happen.
- estebank 6y agoThe gp is slightly incorrect: in Rust you cannot override the constructor so that it allocates more than the struct itself. You can extend + and allocate in it, which is why it is treated in theory and practice as if it were a method call, because it is. You cannot override the assignment operator, it will always be either a conceptual move of ownership or a memcopy at worst, never a method call with any arbitrary number of heap allocations. Same for the dereferencing operator, it cannot be overriden. This is the reason we say there are no hidden allocations in Rust. In every language you might have allocations in a method call. Some languages consider assignment to be one for example, Rust doesn't.
- jcelerier 6y agoThis doesn't make a lot of sense to me. If a language has a feature, people will use it, encouraged or not. So I really don't see the argument there.
- estebank 6y agoOf the examples given, Rust can only do the first one, overrides + because it is treated as just another method call. Assignments struct constructors and dereferencing always do what they look like they are doing as they cannot be overriden.
- a1369209993 6y ago> If a language has a feature, people will use it You can also use asm blocks (or string literals casted to function pointers) to wreak all kinds of havok. Oddly, noone seems particularly concerned about that.