[Mesa-dev] Rust drivers in Mesa

Konstantin Kharlamov hi-angel at yandex.ru
Sat Oct 3 21:28:15 UTC 2020

On Sat, 2020-10-03 at 00:51 +0200, timur.kristof at gmail.com wrote:
> The Rust syntax is slightly annoying. They departed from C/C++ enough
> to make Rust look different, but then they got lazy and for some reason
> they chose to keep the most annoying parts from C/C++ like curly braces
> and semicolons, so even if we switch to Rust we can still enjoy
> debating important topics like where to put curly braces, how many
> spaces or tabs are best, and so on.

Unlike C++ though, Rust have reason for semicolons. In Rust you can write a
subexpression, whose result gets assigned to a variable, and you "return" this
result from the subexpression by omitting semicolon. In C++ you have to use a
lambda for that.

Talking of syntax, it may not be ideal, but since you compare it to C++, Rust
syntax is better. Off the top of my head:

1. No "const" modifiers, everything is immutable by default, which is how modern
   language should look like (because really, most of the things you work with in
   a function are either never modified (e.g. some arguments) or only upon
   creation — i.e. basically never too)
2. No braces in if-conditions. So you have one less pair of braces to eyeball
   while reading complex `if ((foo()+x) && (bar()) || buzz())` statements.
3. Lambda syntax is less to write and to read: less brackets/braces.
4. Way better syntax for Algebraic Data Types. E.g. in C++ you might have a
   `std::variant<Foo, Bar, Buzz> MyADT`, where all thee fields are ultimately
   anonymous, they only have type. In Rust on the other hand you have a `enum
   MyADT {Event1(Foo), Event2(bar), Event3(Buzz)}`, and you know what these types
   actually represent.
   I recall in modern C++ you can use `union`, but then you have to wrap it with
   something that tracks the field currently set; and I guess that alone shows it
   is more to write than in Rust.
These are just something I remember offhand, I'm sure there're more examples
regarding syntax.

> My main concern is that memory is just one of many resources that we
> need to use safely, but it's the only one that Rust concerns itself
> with. Memory safety can give you a false sense of security. It's
> possible to write insecure apps that are perfectly memory safe.

Well, this is a correct thought, but I don't see what point are you trying to
make here. I mean, you can write a bad program in any existing language,
sure. Rust gets rid of one possible problem, so… one problem less is good, I

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