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Hir::is_match_empty returns false for \b, but should return true #859
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BurntSushi
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This was incorrectly defined for \b. Previously, I had erroneously made it return true only for \B since \B matches '' and \b does not match ''. However, \b does match the empty string. Like \B, it only matches a subset of empty strings, depending on what the surrounding context is. The important bit is that it can match *an* empty string, not that it matches *the* empty string. We were not yet using this predicate anywhere in the regex crate, so we just fix the implementation and update the tests. This does present a compatibility hazard for anyone who was using this function, but as of this time, I'm considering this a bug fix since \b clearly matches an empty string. Fixes #859
BurntSushi
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May 18, 2022
This was incorrectly defined for \b. Previously, I had erroneously made it return true only for \B since \B matches '' and \b does not match ''. However, \b does match the empty string. Like \B, it only matches a subset of empty strings, depending on what the surrounding context is. The important bit is that it can match *an* empty string, not that it matches *the* empty string. We were not yet using this predicate anywhere in the regex crate, so we just fix the implementation and update the tests. This does present a compatibility hazard for anyone who was using this function, but as of this time, I'm considering this a bug fix since \b clearly matches an empty string. Fixes #859
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Jun 7, 2022
Bump regex from 1.5.4 to 1.5.6 Bumps regex from 1.5.4 to 1.5.6. Changelog Sourced from regex's changelog. 1.5.6 (2022-05-20) This release includes a few bug fixes, including a bug that produced incorrect matches when a non-greedy ? operator was used. [BUG #680](rust-lang/regex#680): Fixes a bug where [[:alnum:][:^ascii:]] dropped [:alnum:] from the class. [BUG #859](rust-lang/regex#859): Fixes a bug where Hir::is_match_empty returned false for \b. [BUG #862](rust-lang/regex#862): Fixes a bug where 'ab??' matches 'ab' instead of 'a' in 'ab'. 1.5.5 (2022-03-08) This releases fixes a security bug in the regex compiler. This bug permits a vector for a denial-of-service attack in cases where the regex being compiled is untrusted. There are no known problems where the regex is itself trusted, including in cases of untrusted haystacks. SECURITY #GHSA-m5pq-gvj9-9vr8: Fixes a bug in the regex compiler where empty sub-expressions subverted the existing mitigations in place to enforce a size limit on compiled regexes. The Rust Security Response WG published an advisory about this: https://groups.google.com/g/rustlang-security-announcements/c/NcNNL1Jq7Yw Commits 9aef5b1 1.5.6 2931b07 syntax: bump minimum regex-syntax version to 0.6.26 b41bde0 regex-syntax-0.6.26 d98da65 changelog: 1.5.6 1c19619 syntax: fix literal extraction for 'ab??' 88a2a62 syntax: fix 'is_match_empty' predicate 72f09f1 syntax: fix ascii class union bug b537286 doc: fix some typos 258bdf7 changelog: 1.5.5 d130381 1.5.5 Additional commits viewable in compare view Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase. Dependabot commands and options You can trigger Dependabot actions by commenting on this PR: @dependabot rebase will rebase this PR @dependabot recreate will recreate this PR, overwriting any edits that have been made to it @dependabot merge will merge this PR after your CI passes on it @dependabot squash and merge will squash and merge this PR after your CI passes on it @dependabot cancel merge will cancel a previously requested merge and block automerging @dependabot reopen will reopen this PR if it is closed @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself) @dependabot use these labels will set the current labels as the default for future PRs for this repo and language @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language You can disable automated security fix PRs for this repo from the Security Alerts page. Reviewed-by: Artem Goncharov <Artem.goncharov@gmail.com>
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The predicate in question: https://docs.rs/regex-syntax/latest/regex_syntax/hir/struct.Hir.html#method.is_match_empty
The issue here is that
is_match_empty
returns true for\B
but not for\b
. I had done this because\B
matches""
but\b
does not. However, as of version 1.5.5, this program runs without panicking:Playground link.
Thus proving that
\b
does indeed report matches that correspond to the empty string. Therefore, it is a bug thatis_match_empty
returnsfalse
for\b
. The issue here is that neither\B
nor\b
match every empty string. Instead, they only match a subset of empty strings.The text was updated successfully, but these errors were encountered: