4 ms·

"Undefined behavior" in C++ just means stuff that's either CPU-specific or compiler-specific. Rust has no undefined behavior because it only supports one CPU a

"Undefined behavior" in C++ just means stuff that's either CPU-specific or compiler-specific. Rust has no undefined behavior because it only supports one CPU and has only one compiler implementation. When Rust supports a dozen architectures and has three different compiler implementations then Rust will be just as full of UB as C++. Except with the added "bonus" of all the UB being brand-new and unspecified, unlike the well-known portability pitfalls of C++.

dagenix 8y ago
> Rust has no undefined behavior because it only supports one CPU ... That is not true. Rust works on multiple architectures.
- otabdeveloper2 8y ago
  There's a massive chasm between "works on" and "supports".
  - Retra 8y ago
    That doesn't seem relevant -- Rust works on and supports multiple architectures. And there's plenty of UB in unsafe code.
pcein 8y ago
I am happily running Rust generated code on my ARM microcontrollers. Rust uses LLVM for code generation and can support any architecture which LLVM supports.
pjmlp 8y ago
There are plenty of system languages with a very tiny percentage of UB vs all the languages that allow for copy-paste of C code. Because they prefer to loose a couple of ms to paying the price of the ultimate performance might bring. Like in real life you can speed at 300 KMH with a 1200cc motorbike, or doing it a car with reinforced structure wearing seatbelts and airbags. Even with diminished chances of survival, I rather be in the car.
- otabdeveloper2 8y ago
  UB is an implementation issue, not a language issue. UB is a fact of life that cannot be removed by overspecifying a language -- if your language spec has too much implementation-specific stuff in it, then compiler writers will simply ignore it. Many such examples. The best you can do is to document the implementation-specific stuff extensively. Also, implementation-specific details aren't always about maximizing performance. Compilers implement languages slightly differently because of architecture and OS differences and because it's easier that way for the people writing compilers.
  - pjmlp 8y ago
    UB is not implementation specific at all, the ISO documentation is quite clear about which is which. Other systems languages manage to do it quite well. It was really a shame that Bell Labs gave UNIX away for a symbolic price during 10 years before being allowed to actually sell it. We wouldn't be having this kind of C related talks.
steveklabnik 8y ago
> When Rust supports a dozen architectures "Rust now available on 14 Debian architectures" https://lists.debian.org/debian-devel-announce/2018/11/msg00000.html https://lists.debian.org/debian-devel-announce/2018/11/msg00...

dagenix 8y ago

> Rust has no undefined behavior because it only supports one CPU ... That is not true. Rust works on multiple architectures.

otabdeveloper2 8y ago
There's a massive chasm between "works on" and "supports".
- Retra 8y ago
  That doesn't seem relevant -- Rust works on and supports multiple architectures. And there's plenty of UB in unsafe code.

pcein 8y ago

I am happily running Rust generated code on my ARM microcontrollers. Rust uses LLVM for code generation and can support any architecture which LLVM supports.

pjmlp 8y ago

There are plenty of system languages with a very tiny percentage of UB vs all the languages that allow for copy-paste of C code. Because they prefer to loose a couple of ms to paying the price of the ultimate performance might bring. Like in real life you can speed at 300 KMH with a 1200cc motorbike, or doing it a car with reinforced structure wearing seatbelts and airbags. Even with diminished chances of survival, I rather be in the car.

otabdeveloper2 8y ago
UB is an implementation issue, not a language issue. UB is a fact of life that cannot be removed by overspecifying a language -- if your language spec has too much implementation-specific stuff in it, then compiler writers will simply ignore it. Many such examples. The best you can do is to document the implementation-specific stuff extensively. Also, implementation-specific details aren't always about maximizing performance. Compilers implement languages slightly differently because of architecture and OS differences and because it's easier that way for the people writing compilers.
- pjmlp 8y ago
  UB is not implementation specific at all, the ISO documentation is quite clear about which is which. Other systems languages manage to do it quite well. It was really a shame that Bell Labs gave UNIX away for a symbolic price during 10 years before being allowed to actually sell it. We wouldn't be having this kind of C related talks.

steveklabnik 8y ago

> When Rust supports a dozen architectures "Rust now available on 14 Debian architectures" https://lists.debian.org/debian-devel-announce/2018/11/msg00000.html https://lists.debian.org/debian-devel-announce/2018/11/msg00...