ffi: pass non-empty slice when haystack is empty#43
Merged
BurntSushi merged 1 commit intomasterfrom Jul 30, 2024
Merged
Conversation
To work around likely bugs in (older versions of) PCRE2. Namely, at one point, PCRE2 would dereference the haystack pointer even when the length was zero. This was reported in #10 and we worked around this in #11 by passing a pointer to a const `&[]`, with the (erroneous) presumption that this would be a valid pointer to dereference. In retrospect though, this was a little silly, because you should never be dereferencing a pointer to an empty slice. It's not valid. Alas, at that time, Rust did actually hand you a valid pointer that could be dereferenced. But [this PR][rust-pull] changed that. And thus, we're back to where we started: handing buggy versions of PCRE2 a zero length haystack with a dangling pointer. So we fix this once and for all by passing a slice of length 1, but with a haystack length of 0, to the PCRE2 search routine when searching an empty haystack. This will guarantee the provision of a dereferencable pointer should PCRE2 decide to dereference it. Fixes #42 [rust-pull]: rust-lang/rust#123936
This file contains hidden or 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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
To work around likely bugs in (older versions of) PCRE2. Namely, at one
point, PCRE2 would dereference the haystack pointer even when the length
was zero.
This was reported in #10 and we worked around this in #11 by passing a
pointer to a const
&[], with the (erroneous) presumption that thiswould be a valid pointer to dereference. In retrospect though, this was
a little silly, because you should never be dereferencing a pointer to
an empty slice. It's not valid. Alas, at that time, Rust did actually
hand you a valid pointer that could be dereferenced. But this
PR changed that. And thus, we're back to where we started:
handing buggy versions of PCRE2 a zero length haystack with a dangling
pointer.
So we fix this once and for all by passing a slice of length 1, but with
a haystack length of 0, to the PCRE2 search routine when searching an
empty haystack. This will guarantee the provision of a dereferencable
pointer should PCRE2 decide to dereference it.
Fixes #42