4 ms·

Yep. For example, it's easy to make intentional memory leak in Rust using safe API, which is unsafe. However, it's also easy to find such memory leak. Rust cann

by drran 6y ago

Yep. For example, it's easy to make intentional memory leak in Rust using safe API, which is unsafe. However, it's also easy to find such memory leak. Rust cannot stop you from doing weird things, when you want this, but it can help you to prevent, or quickly find, weird things, when you don't want them in your code.

EE84M3i 6y ago
"For example, it's easy to make intentional memory leak in Rust using safe API, which is unsafe." In what way is leaking memory in rust unsafe?
- drran 6y ago
  It's a safe way to crash program by OOM killer. :-)
Const-me 6y ago
> However, it's also easy to find such memory leak. How? By manually inspecting all code in the project + dependencies marked with "unsafe"? The approach doesn't scale past "hello world" level of complexity. I don't code Rust, using C# for same purpose. I remember couple times I spend hours debugging weird crashes caused by stupid bugs in totally unrelated unsafe C# code. It's much easier to find memory leaks or native memory corruptions in C++, than in unsafe subset of a memory safe language. C++ has lots of runtime support for that (especially in debug builds), and many great tools, both in the compilers and external ones. Unsafe C# has none of them.
- steveklabnik 6y ago
  You can also use those tools on Rust. It looks close enough that’s it’s fine. Valgrind, fuzzers, that stuff still works.
  - Const-me 6y ago
    Simpler stuff like debug C heap, and checked iterators in C++ standard library, catch 95% of memory corruption issues in C++. These are enabled by default in debug builds, very often just pressing F5 in visual studio finds the buggy line of code in a matter of seconds. Valgrind is Linux-only, I don’t have it. One Windows equivalent is memory profiler under Debug / Performance Profiler / Memory Usage in visual studio, Rust is not supported by visual studio. A cross-platform equivalent is Intel VTune Profiler, no support for Rust either.
    - steveklabnik 6y ago
      I mean, if you’re talking about checked iterators... that’s checked in Rust too. I am 100% Windows, but don’t triage these issues often enough to suggest tools; the unsafe code I write tends to be small and pretty obvious. (More like “write to this register” than “here’s a complex data structure.”)
      - Const-me 6y ago
        > that’s checked in Rust too In safe Rust. Safe C# is the same, it doesn’t even have raw pointers in the language unless compiling with /unsafe, and writing code in unsafe blocks. > More like “write to this register” than “here’s a complex data structure.” I sometimes write C++ DLLs precisely to implement these complex data structures. Modern CPUs have progressively worse proportion of RAM latency / compute speed. This means you need full control over memory layout of data on the performance critical paths of code, or it will be slow. Also, many external APIs have incredibly complex unsafe structures. Here’s a piece of Linux kernel API I have recently consumed in C#: https://www.kernel.org/doc/html/v4.20/media/uapi/v4l/v4l2.html https://www.kernel.org/doc/html/v4.20/media/uapi/v4l/v4l2.ht... Way more complicated than writing registers.
        steveklabnik 6y ago
        They’re checked in unsafe too. You only skip those checks if you use a specific “do this index with no checks” function. Unsafe does not change the semantics of code, only gives you more options. Yes, and many people write that kind of code in Rust too, and use tools to help them debug it. I’m just saying that it’s not an issue for the kinds of code I write, so I can’t personally recommend tooling. I know "use GDB" isn't a great response to a Windows user, even if it is what I end up personally doing. Funny enough, I just booted up VS, and it's not perfect, but https://imgur.com/a/kHvPIEr https://imgur.com/a/kHvPIEr (It's true that I can't get the performance tools working though, but given I've used VS for all of 20 minutes... I'm also very interested to see if support happens native-ly, given how much interest there is for Rust inside of Microsoft right now.)
qppo 6y ago
Memory leaks are not memory unsafe.

by drran 6y ago

EE84M3i 6y ago

"For example, it's easy to make intentional memory leak in Rust using safe API, which is unsafe." In what way is leaking memory in rust unsafe?

drran 6y ago
It's a safe way to crash program by OOM killer. :-)

Const-me 6y ago

> However, it's also easy to find such memory leak. How? By manually inspecting all code in the project + dependencies marked with "unsafe"? The approach doesn't scale past "hello world" level of complexity. I don't code Rust, using C# for same purpose. I remember couple times I spend hours debugging weird crashes caused by stupid bugs in totally unrelated unsafe C# code. It's much easier to find memory leaks or native memory corruptions in C++, than in unsafe subset of a memory safe language. C++ has lots of runtime support for that (especially in debug builds), and many great tools, both in the compilers and external ones. Unsafe C# has none of them.

steveklabnik 6y ago
You can also use those tools on Rust. It looks close enough that’s it’s fine. Valgrind, fuzzers, that stuff still works.
- Const-me 6y ago
  Simpler stuff like debug C heap, and checked iterators in C++ standard library, catch 95% of memory corruption issues in C++. These are enabled by default in debug builds, very often just pressing F5 in visual studio finds the buggy line of code in a matter of seconds. Valgrind is Linux-only, I don’t have it. One Windows equivalent is memory profiler under Debug / Performance Profiler / Memory Usage in visual studio, Rust is not supported by visual studio. A cross-platform equivalent is Intel VTune Profiler, no support for Rust either.
  - steveklabnik 6y ago
    I mean, if you’re talking about checked iterators... that’s checked in Rust too. I am 100% Windows, but don’t triage these issues often enough to suggest tools; the unsafe code I write tends to be small and pretty obvious. (More like “write to this register” than “here’s a complex data structure.”)
    - Const-me 6y ago
      > that’s checked in Rust too In safe Rust. Safe C# is the same, it doesn’t even have raw pointers in the language unless compiling with /unsafe, and writing code in unsafe blocks. > More like “write to this register” than “here’s a complex data structure.” I sometimes write C++ DLLs precisely to implement these complex data structures. Modern CPUs have progressively worse proportion of RAM latency / compute speed. This means you need full control over memory layout of data on the performance critical paths of code, or it will be slow. Also, many external APIs have incredibly complex unsafe structures. Here’s a piece of Linux kernel API I have recently consumed in C#: https://www.kernel.org/doc/html/v4.20/media/uapi/v4l/v4l2.html https://www.kernel.org/doc/html/v4.20/media/uapi/v4l/v4l2.ht... Way more complicated than writing registers.
      - steveklabnik 6y ago
        They’re checked in unsafe too. You only skip those checks if you use a specific “do this index with no checks” function. Unsafe does not change the semantics of code, only gives you more options. Yes, and many people write that kind of code in Rust too, and use tools to help them debug it. I’m just saying that it’s not an issue for the kinds of code I write, so I can’t personally recommend tooling. I know "use GDB" isn't a great response to a Windows user, even if it is what I end up personally doing. Funny enough, I just booted up VS, and it's not perfect, but https://imgur.com/a/kHvPIEr https://imgur.com/a/kHvPIEr (It's true that I can't get the performance tools working though, but given I've used VS for all of 20 minutes... I'm also very interested to see if support happens native-ly, given how much interest there is for Rust inside of Microsoft right now.)

qppo 6y ago

Memory leaks are not memory unsafe.