this post was submitted on 28 Aug 2023
54 points (96.6% liked)

Programming

17489 readers
95 users here now

Welcome to the main community in programming.dev! Feel free to post anything relating to programming here!

Cross posting is strongly encouraged in the instance. If you feel your post or another person's post makes sense in another community cross post into it.

Hope you enjoy the instance!

Rules

Rules

  • Follow the programming.dev instance rules
  • Keep content related to programming in some way
  • If you're posting long videos try to add in some form of tldr for those who don't want to watch videos

Wormhole

Follow the wormhole through a path of communities [email protected]

founded 1 year ago
MODERATORS
snowe
Ategon
[email protected]
54
The Little Things: The Missing Performance in std::vector (codingnest.com)
submitted 1 year ago by MarekKnapek to c/programming
11 comments fedilink hide all child comments
you are viewing a single comment's thread
view the rest of the comments
[–] kornel 6 points 1 year ago* (last edited 1 year ago) (1 children)

I don't know about C++, but in Rust the push is inline, and still doesn't always optimize checks away due to an annoying edge case: integer overflow. Reserving (old_len + new_len) could give you a smaller buffer than new_len. The optimizer sees it and is pedantic about it.

[–] robinm 1 points 1 year ago (1 children)

In C++ integer overflow is UB so this edge case cannot exist

[–] kornel 3 points 1 year ago (1 children)

Only signed overflow. size_t is unsigned.

[–] robinm 1 points 1 year ago* (last edited 1 year ago)

That's totally right but I thought you were talking about signed numbers since you said “integer overflow”. I forgot that len is usually unsigned in C++.