coverage: Avoid overflow when the MC/DC condition limit is exceeded by Zalathar · Pull Request #125700

coverage: Avoid overflow when the MC/DC condition limit is exceeded by Zalathar · Pull Request #125700 · rust-lang/rust

rustbot added S-waiting-on-review

Status: Awaiting review from the assignee but also interested parties.

T-compiler

Relevant to the compiler team, which will review and decide on the PR/issue.

A-code-coverage

Area: Source-based code coverage (-Cinstrument-coverage)

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May 29, 2024

If we perform this subtraction and then add 1, the subtraction can sometimes
overflow to -1 before the addition can bring its value back to 0. That
behaviour seems to be benign, but it nevertheless causes test failures in
compiler configurations that check for overflow.

We can avoid the overflow by instead subtracting (N - 1), which is
algebraically equivalent, and more closely matches what the code is actually
trying to do.

bors added S-waiting-on-bors

Status: Waiting on bors to run and complete tests. Bors will change the label on completion.

and removed S-waiting-on-review

Status: Awaiting review from the assignee but also interested parties.

labels

May 29, 2024

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

May 29, 2024

…cote

coverage: Avoid overflow when the MC/DC condition limit is exceeded

Fix for the test failure seen in rust-lang#124571 (comment).

If we perform this subtraction first, it can sometimes overflow to -1 before the addition can bring its value back to 0.

That behaviour seems to be benign, but it nevertheless causes test failures in compiler configurations that check for overflow.

`@rustbot` label +A-code-coverage

bors added a commit to rust-lang-ci/rust that referenced this pull request

May 29, 2024

…iaskrgr

Rollup of 6 pull requests

Successful merges:

 - rust-lang#107099 (rustdoc: Add support for --remap-path-prefix)
 - rust-lang#125693 (Format all source files in `tests/coverage/`)
 - rust-lang#125700 (coverage: Avoid overflow when the MC/DC condition limit is exceeded)
 - rust-lang#125705 (Reintroduce name resolution check for trying to access locals from an inline const)
 - rust-lang#125708 (tier 3 target policy: clarify the point about producing assembly)
 - rust-lang#125715 (remove unneeded extern crate in rmake test)

r? `@ghost`
`@rustbot` modify labels: rollup

bors added a commit to rust-lang-ci/rust that referenced this pull request

May 29, 2024

…iaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#124655 (Add `-Zfixed-x18`)
 - rust-lang#125693 (Format all source files in `tests/coverage/`)
 - rust-lang#125700 (coverage: Avoid overflow when the MC/DC condition limit is exceeded)
 - rust-lang#125705 (Reintroduce name resolution check for trying to access locals from an inline const)
 - rust-lang#125708 (tier 3 target policy: clarify the point about producing assembly)
 - rust-lang#125715 (remove unneeded extern crate in rmake test)
 - rust-lang#125719 (Extract coverage-specific code out of `compiletest::runtest`)

r? `@ghost`
`@rustbot` modify labels: rollup

rust-timer added a commit to rust-lang-ci/rust that referenced this pull request

May 29, 2024

Rollup merge of rust-lang#125700 - Zalathar:limit-overflow, r=nnethercote

coverage: Avoid overflow when the MC/DC condition limit is exceeded

Fix for the test failure seen in rust-lang#124571 (comment).

If we perform this subtraction first, it can sometimes overflow to -1 before the addition can bring its value back to 0.

That behaviour seems to be benign, but it nevertheless causes test failures in compiler configurations that check for overflow.

``@rustbot`` label +A-code-coverage

bors added S-waiting-on-author

Status: This is awaiting some action (such as code changes or more information) from the author.

and removed S-waiting-on-bors

Status: Waiting on bors to run and complete tests. Bors will change the label on completion.

labels

May 29, 2024

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

May 30, 2024

coverage: Rename MC/DC `conditions_num` to `num_conditions`

Updated version of rust-lang#124571, without the other changes that were split out into rust-lang#125108 and rust-lang#125700.

This value represents a quantity of conditions, not an ID, so the new spelling is more appropriate.

Some of the code touched by this PR could perhaps use some other changes, but I would prefer to keep this PR as a simple renaming and avoid scope creep.

`@rustbot` label +A-code-coverage

rust-timer added a commit to rust-lang-ci/rust that referenced this pull request

May 30, 2024

Rollup merge of rust-lang#125754 - Zalathar:conditions-num, r=lqd

coverage: Rename MC/DC `conditions_num` to `num_conditions`

Updated version of rust-lang#124571, without the other changes that were split out into rust-lang#125108 and rust-lang#125700.

This value represents a quantity of conditions, not an ID, so the new spelling is more appropriate.

Some of the code touched by this PR could perhaps use some other changes, but I would prefer to keep this PR as a simple renaming and avoid scope creep.

`@rustbot` label +A-code-coverage