add no_std regex, which depends on alloc #476
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My rough prediction is that the pattern of an The details of implementing a global allocator that can be used with the global facade pattern are definitely in flux, but I've not seen dramatic change in how general-purpose libraries consume them recently. As @BurntSushi rightly pointed out, the primary hassle here is maintaining all of those conditional-compilation flags. I'll explore some more to see if there are any other tricks available for reducing their proliferation, and tear out |
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Some good news is that the approach speculated in my prior comment seems to have borne some dividends, as seen by comparing the first and second commit of the no_std PR to regex-syntax. The original approach added ~230 lines, the latest approach adds only ~100. Removing the |
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Nice. :) To clarify, I could probably stomach cfg-if itself. It is widely used and I trust its caretaker. But I try hard to be conservative here, especially with regex since it is so widely used. In my experience maintaining things, dependencies have generally become a liability. The only reason regex has as many dependencies as it does is because most of them would need to exist internally anyway, and it makes sense to expose them for others to benefit from. |
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For completeness, I asked around the portability working group about the state of viable alternatives, and was pointed in the direction of the following documents:
The described end-state of thorough and flexible capability-aware portability is extremely appealing. It would encourage a consistent approach to configuration across libraries and probably reduce the redundantly-retargeted- That said, the overall approach of using human-applied The working group seems to be in "design and ground-work" phase, clearing out various obstacles but not yet tackling the primary implementation. Thus, at present, I find it difficult to estimate the timeline involved before the vision approaches realization. |
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After looking around a bit more, it seems like in some ways the community is voting with its commits. Two other relatively high profile projects in the ecosystem -- rand and nom appear to be moving forward with the "std"-as-default-feature, "alloc"-as-optional-feature approach. This gives me some confidence that either the strategy has momentum, or the projected maintenance burden for that pattern is tolerable. Perhaps @Geal or @pitdicker or @dhardy wouldn't mind commenting? |
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Not sure what the exact issue is to reply to, but I'll try writing something. I think supporting One thing that does help is that Rand doesn't really require allocations. Adding the
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Thanks for all the references @ZackPierce; Aaron's "portability vision" article is why I suggested importing from The size of #477 could probably be smaller still in my opinion, except some more changes may be needed in tests. As @pitdicker mentions, as a result of this you end up with two test suites to run, i.e. CI doesn't need to be as complex as we have in Rand, though if you care about testing several different platforms you may want to take notes from Rand's Travis configuration. |
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@ZackPierce recently added I'd like to replicate Zack's work in I'll start working on a PR to this end. :) |
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Thanks you for chiming in with your experiences and suggestions, @dhardy , @pitdicker , and @Centril . As of the latest updates based on those ideas, the exemplar PR to the regex-syntax crate now has roughly 25% of the code changes to the extant, operational portion of the codebase as when it was first attempted. Seems like a pretty respectable improvement in the cognitive load cost for maintenance to me. |
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One other thing I thought about here is the regex's crate's use of the |
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If anyone has specific application oriented use cases for (I don't have any application oriented use cases myself. My goal here was to service others.) |
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(Idk if it counts as an application oriented use case or not, but |
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@Centril I think I would just ask you to push the question forward, since |
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@BurntSushi I redirect to @ZackPierce since they introduced the Some relevant discussion: proptest-rs/proptest#47 |
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@BurntSushi |
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Sorry, but that seems off topic for this issue? I don't understand what question, if any, you're asking me. If you need help with something, then please open a new issue and provide as much detail as possible about the problem you're trying to solve and your constraints. |
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Sorry, I ought to make it cleaner. I just described our use case for using |
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@harryfei Sorry, but I'm going to need a lot more details than that. I'm not a Windows programmer, and certainly have no experience with Windows kernel driver development, so I don't understand what your constraints are. |
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Presumably the only relevant constraint is whether or not you have |
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In kernel driver development, we must use |
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@harryfei Thanks for elaborating. I think you'll want to monitor rust-lang/rfcs#2480. Once it stabilizes, then this is something I'd be willing to more aggressively pursue. |
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@harryfei @BurntSushi the alloc crate got stabilized in the last release of rustc so it might be worth pursueing this further as you mentioned before. |
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Yes I know. It will likely be a while before I look into it. regex has a conservative MSRV. |
Would it not be possible to use |
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Yes. |
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
In effect, this adds support for no_std by depending on only core and alloc. There is still currently some benefit to enabling std support, namely, getting the 'std::error::Error' trait impls for the various error types. (Although, it seems like the 'Error' trait is going to get moved to 'core' finally.) Otherwise, the only 'std' things we use are in tests for tweaking stack sizes. This is the first step in an effort to make 'regex' itself work without depending on 'std'. 'regex' itself will be more precarious since it uses things like HashMap and Mutex that we'll need to find a way around. Getting around HashMap is easy (just use BTreeMap), but figuring out how to synchronize the threadpool will be interesting. Ref #476, Ref #477
I usually close tickets on a commit-by-commit basis, but this refactor was so big that it wasn't feasible to do that. So ticket closures are marked here. Closes #244 Closes #259 Closes #476 Closes #644 Closes #675 Closes #824 Closes #961 Closes #68 Closes #510 Closes #787 Closes #891 Closes #429 Closes #517 Closes #579 Closes #779 Closes #850 Closes #921 Closes #976 Closes #1002 Closes #656
This PR contains the following updates: | Package | Type | Update | Change | |---|---|---|---| | [regex](https://github.com/rust-lang/regex) | dependencies | minor | `1.8.4` -> `1.9.1` | --- ### Release Notes <details> <summary>rust-lang/regex (regex)</summary> ### [`v1.9.1`](https://github.com/rust-lang/regex/blob/HEAD/CHANGELOG.md#191-2023-07-07) [Compare Source](rust-lang/regex@1.9.0...1.9.1) \================== This is a patch release which fixes a memory usage regression. In the regex 1.9 release, one of the internal engines used a more aggressive allocation strategy than what was done previously. This patch release reverts to the prior on-demand strategy. Bug fixes: - [BUG #​1027](rust-lang/regex#1027): Change the allocation strategy for the backtracker to be less aggressive. ### [`v1.9.0`](https://github.com/rust-lang/regex/blob/HEAD/CHANGELOG.md#190-2023-07-05) [Compare Source](rust-lang/regex@1.8.4...1.9.0) \================== This release marks the end of a [years long rewrite of the regex crate internals](rust-lang/regex#656). Since this is such a big release, please report any issues or regressions you find. We would also love to hear about improvements as well. In addition to many internal improvements that should hopefully result in "my regex searches are faster," there have also been a few API additions: - A new `Captures::extract` method for quickly accessing the substrings that match each capture group in a regex. - A new inline flag, `R`, which enables CRLF mode. This makes `.` match any Unicode scalar value except for `\r` and `\n`, and also makes `(?m:^)` and `(?m:$)` match after and before both `\r` and `\n`, respectively, but never between a `\r` and `\n`. - `RegexBuilder::line_terminator` was added to further customize the line terminator used by `(?m:^)` and `(?m:$)` to be any arbitrary byte. - The `std` Cargo feature is now actually optional. That is, the `regex` crate can be used without the standard library. - Because `regex 1.9` may make binary size and compile times even worse, a new experimental crate called `regex-lite` has been published. It prioritizes binary size and compile times over functionality (like Unicode) and performance. It shares no code with the `regex` crate. New features: - [FEATURE #​244](rust-lang/regex#244): One can opt into CRLF mode via the `R` flag. e.g., `(?mR:$)` matches just before `\r\n`. - [FEATURE #​259](rust-lang/regex#259): Multi-pattern searches with offsets can be done with `regex-automata 0.3`. - [FEATURE #​476](rust-lang/regex#476): `std` is now an optional feature. `regex` may be used with only `alloc`. - [FEATURE #​644](rust-lang/regex#644): `RegexBuilder::line_terminator` configures how `(?m:^)` and `(?m:$)` behave. - [FEATURE #​675](rust-lang/regex#675): Anchored search APIs are now available in `regex-automata 0.3`. - [FEATURE #​824](rust-lang/regex#824): Add new `Captures::extract` method for easier capture group access. - [FEATURE #​961](rust-lang/regex#961): Add `regex-lite` crate with smaller binary sizes and faster compile times. - [FEATURE #​1022](rust-lang/regex#1022): Add `TryFrom` implementations for the `Regex` type. Performance improvements: - [PERF #​68](rust-lang/regex#68): Added a one-pass DFA engine for faster capture group matching. - [PERF #​510](rust-lang/regex#510): Inner literals are now used to accelerate searches, e.g., `\w+@​\w+` will scan for `@`. - [PERF #​787](rust-lang/regex#787), [PERF #​891](rust-lang/regex#891): Makes literal optimizations apply to regexes of the form `\b(foo|bar|quux)\b`. (There are many more performance improvements as well, but not all of them have specific issues devoted to them.) Bug fixes: - [BUG #​429](rust-lang/regex#429): Fix matching bugs related to `\B` and inconsistencies across internal engines. - [BUG #​517](rust-lang/regex#517): Fix matching bug with capture groups. - [BUG #​579](rust-lang/regex#579): Fix matching bug with word boundaries. - [BUG #​779](rust-lang/regex#779): Fix bug where some regexes like `(re)+` were not equivalent to `(re)(re)*`. - [BUG #​850](rust-lang/regex#850): Fix matching bug inconsistency between NFA and DFA engines. - [BUG #​921](rust-lang/regex#921): Fix matching bug where literal extraction got confused by `$`. - [BUG #​976](rust-lang/regex#976): Add documentation to replacement routines about dealing with fallibility. - [BUG #​1002](rust-lang/regex#1002): Use corpus rejection in fuzz testing. </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate). <!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNi4wLjAiLCJ1cGRhdGVkSW5WZXIiOiIzNi44LjExIiwidGFyZ2V0QnJhbmNoIjoiZGV2ZWxvcCJ9--> Co-authored-by: cabr2-bot <[email protected]> Co-authored-by: crapStone <[email protected]> Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1957 Reviewed-by: crapStone <[email protected]> Co-authored-by: Calciumdibromid Bot <[email protected]> Co-committed-by: Calciumdibromid Bot <[email protected]>
There has been some interest in putting out a version of regex that doesn't depend on std itself, but instead depends just on alloc. This is within reach because regex already doesn't rely too much on platform specific details, and mostly just depends on dynamic memory allocation. There are however some parts of the regex API that will need to be tweaked. For example, regex uses
std::io::Error, which isn't available inalloc. This is why regex 1.0 got ause_std/stdfeature. Namely, compiling regex without that feature fails today. This will allow us to change the semantics of that compilation mode without breaking backwards compatibility.@ZackPierce has been diligently adding support for this by starting with regex's dependencies. So far:
I thought it would be good to track this issue at a higher level so we can discuss a game plan. I'd also like to share some of my thoughts/constraints on the process.
I basically think that we should do this. What I am unsure of is the timeline. For the most part, my own personal maintenance bandwidth is very limited, and to this end, I've generally avoided nightly-only support of things. (I've made some exceptions. Support for things like
Patternhappened before I knew better, and support for SIMD happened because I am very excited about it and got involved with the SIMD stabilization effort.) Namely, I cannot and will not be beholden to nightly breakages because I simply can't keep up. To that end, I would like to know more about what the plan is forno_stdenvironments. Is thealloccrate setup generally where we think we're going? If so, and if it remains relatively stable, I think I could get on board with this relatively soon.It's also worth saying that some changes are simpler than others. For example, making
utf8-rangescompatible withno_stdis pretty reasonable, but theaho-corasickchanges are quite a bit broader. I have concerns over peppering conditional compilation everywhere, and I think those sorts of things are very hard to maintain. I'm hopeful we can find a better way. This gets worse when the public API is impacted. The complexity and maintenance burden goes way up. This is apparently so bad that it was worth adding a new dependency (cfg-if) that must be paid for by everyone just to support theno_stdusers. I'm not especially excited about that, particularly if the trend continues.For the most part, I really wasn't intending on tackling this feature until more stuff stabilized. But I wanted to get my thoughts out there so that there are no surprises.
I welcome other thoughts on the matter!
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