undefined | Better HN

0 pointsvvanders8y ago0 comments

As someone who's been doing C++ for a close to few decades I's challenge you on that. In C++ you need to understand:

Exceptions(and the runtime/memory costs they incur by pulling in RTTI)

ERRNO(on relevant *nix platforms)

Lifetimes tied to objects when things fail(this is a big one)

Plus any library-specific hackery(I've seen raw strings as errors before)

In contrast I've been writing Rust for ~1.5 years now and each library I've used is consistent and follows common patterns. Much like a lot of people don't grok functional until they understand the common patterns, so it is with Rust too.

0 comments

ahoka8y ago

Exceptions don't need RTTI and have only runtime cost when thrown.

cornstalks8y ago

Exceptions actually can need RTTI, though not necessarily all of the RTTI that things like <typeinfo> provide. For some details, see the -fno-rtti flag for GCC, for which the documentation says[1]:

Disable generation of information about every class with virtual functions for use by the C++ runtime type identification features (`dynamic_cast' and `typeid'). [...] Note that exception handling uses the same information, but it will generate it as needed.

[1]: https://gcc.gnu.org/onlinedocs/gcc-4.6.1/gcc/C_002b_002b-Dia...

pjmlp8y ago

That is a compiler specific implementation, the ANSI C++ standard doesn't require it.

2 more replies

pcwalton8y ago

> Exceptions don't need RTTI and have only runtime cost when thrown.

No, they add extra control flow edges, which inhibit optimizations, affecting runtime performance. This is a lot of the reason why unwinding is optional in Rust.

j / k navigate · click thread line to collapse