Fix integer underflows when rounding up and input is 0 #81277
Closed
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
core/math/math_funcs.h
Outdated
| // 65 / 64 = 2 | ||
| // | ||
| // Will not work correctly if numerator + denominator - 1u results in an overflow. | ||
| static _ALWAYS_INLINE_ uint32_t divide_round_up(uint32_t numerator, uint32_t denominator) { |
There was a problem hiding this comment.
Suggested change
| static _ALWAYS_INLINE_ uint32_t divide_round_up(uint32_t numerator, uint32_t denominator) { | |
| static _ALWAYS_INLINE_ uint32_t divide_round_up(uint32_t p_numerator, uint32_t p_denominator) { |
Prefix arguments with p_, same everywhere
|
Also what is the difference between this and: Which already does this |
Fixes godotengine#80358 Whenever the code wants to round up, it performs x = (x - 1) / y + 1 when it should be doing x = (x + y - 1) / y The original code when the input is 0 is wrong for both unsigned (produces a very large value) and signed (produces 1 instead of 0). This version handles 0 properly. (x / y = 0). Mathematically they're the same: = (x - 1) / y + 1 = (x - 1) / y + y / y = (x + y - 1) / y However in terms of computer science, they're not
darksylinc
force-pushed
the
matias-integer-underflow-round-up
branch
from
a437278 to
e826b64
Compare
It's very simple: I looked for it and I didn't see it. 🤦♂️ I'm closing this one then. |
|
No worries, thank you for your contribution nontheless! In the future check the area to the right on an issue, it lists the PRs linked with this :) |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes #80358
Whenever the code wants to round up, it performs x = (x - 1) / y + 1 when it should be doing x = (x + y - 1) / y
The original code when the input is 0 is wrong for both unsigned (produces a very large value) and signed (produces 1 instead of 0).
This version handles 0 properly. (x / y = 0).
Mathematically they're the same:
= (x - 1) / y + 1
= (x - 1) / y + y / y
= (x + y - 1) / y
However in terms of computer science, they're not