├── .github └── dependabot.yml ├── .gitignore ├── .travis.yml ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md ├── src └── lib.rs └── tests └── smoke.rs /.github/dependabot.yml: -------------------------------------------------------------------------------- 1 | version: 2 2 | updates: 3 | - package-ecosystem: cargo 4 | directory: "/" 5 | schedule: 6 | interval: daily 7 | time: "08:00" 8 | open-pull-requests-limit: 10 9 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | target 2 | Cargo.lock 3 | -------------------------------------------------------------------------------- /.travis.yml: -------------------------------------------------------------------------------- 1 | language: rust 2 | matrix: 3 | include: 4 | - rust: stable 5 | - rust: beta 6 | - rust: nightly 7 | - name: "master doc to gh-pages" 8 | rust: nightly 9 | script: 10 | - cargo doc --no-deps 11 | deploy: 12 | provider: script 13 | script: curl -LsSf https://git.io/fhJ8n | rustc - && (cd target/doc && ../../rust_out) 14 | skip_cleanup: true 15 | on: 16 | branch: master 17 | script: 18 | - cargo build --verbose 19 | - cargo test --verbose 20 | notifications: 21 | email: 22 | on_success: never 23 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "debug-cell" 3 | version = "0.1.1" 4 | authors = ["Alex Crichton "] 5 | license = "MIT/Apache-2.0" 6 | readme = "README.md" 7 | repository = "https://github.com/alexcrichton/debug-cell" 8 | homepage = "https://github.com/alexcrichton/debug-cell" 9 | documentation = "https://docs.rs/debug-cell" 10 | description = """ 11 | A clone of the standard library's `RefCell` type with extra debugging support in 12 | non-release builds. Whenever a borrow error happens the current locations of 13 | where known borrows were created will be printed out as well. 14 | """ 15 | 16 | [dependencies] 17 | backtrace = "0.3" 18 | 19 | [[test]] 20 | name = "smoke" 21 | harness = false 22 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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IN NO EVENT 21 | SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 22 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 23 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 24 | IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 25 | DEALINGS IN THE SOFTWARE. 26 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # debug-cell 2 | 3 | [![Build Status](https://travis-ci.org/alexcrichton/debug-cell.svg?branch=master)](https://travis-ci.org/alexcrichton/debug-cell) 4 | 5 | [Documentation](https://docs.rs/debug-cell) 6 | 7 | A clone of the standard library's `RefCell` type with extra debugging support in 8 | non-release builds. Whenever a borrow error happens the current locations of 9 | where known borrows were created will be printed out as well. 10 | 11 | # License 12 | 13 | This project is licensed under either of 14 | 15 | * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or 16 | http://www.apache.org/licenses/LICENSE-2.0) 17 | * MIT license ([LICENSE-MIT](LICENSE-MIT) or 18 | http://opensource.org/licenses/MIT) 19 | 20 | at your option. 21 | 22 | ### Contribution 23 | 24 | Unless you explicitly state otherwise, any contribution intentionally submitted 25 | for inclusion in Serde by you, as defined in the Apache-2.0 license, shall be 26 | dual licensed as above, without any additional terms or conditions. 27 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT 2 | // file at the top-level directory of this distribution and at 3 | // http://rust-lang.org/COPYRIGHT. 4 | // 5 | // Licensed under the Apache License, Version 2.0 or the MIT license 7 | // , at your 8 | // option. This file may not be copied, modified, or distributed 9 | // except according to those terms. 10 | 11 | //! A clone of the standard library's `RefCell` type with extra debugging 12 | //! support in non-release builds. 13 | //! 14 | //! Whenever a borrow error happens the current 15 | //! locations of where known borrows were created will be printed out as well. 16 | //! 17 | //! # Examples 18 | //! 19 | //! ```no_run 20 | //! use debug_cell::RefCell; 21 | //! 22 | //! let r = RefCell::new(3); 23 | //! let a = r.borrow(); 24 | //! 25 | //! // In debug builds this will print that the cell is currently borrowed 26 | //! // above, and in release builds it will behave the same as the standard 27 | //! // library's `RefCell` 28 | //! let b = r.borrow_mut(); 29 | //! ``` 30 | 31 | #![deny(missing_docs)] 32 | 33 | #[cfg(debug_assertions)] 34 | extern crate backtrace; 35 | 36 | #[cfg(debug_assertions)] 37 | use std::cell::RefCell as StdRefCell; 38 | use std::cell::{Cell, UnsafeCell}; 39 | use std::ops::{Deref, DerefMut}; 40 | 41 | /// A clone of the standard library's `RefCell` type. 42 | pub struct RefCell { 43 | borrow: BorrowFlag, 44 | value: UnsafeCell, 45 | } 46 | 47 | #[cfg(not(debug_assertions))] 48 | type Location = (); 49 | 50 | #[cfg(debug_assertions)] 51 | type Location = backtrace::Backtrace; 52 | 53 | /// An enumeration of values returned from the `state` method on a `RefCell`. 54 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] 55 | pub enum BorrowState { 56 | /// The cell is currently being read, there is at least one active `borrow`. 57 | Reading, 58 | /// The cell is currently being written to, there is an active `borrow_mut`. 59 | Writing, 60 | /// There are no outstanding borrows on this cell. 61 | Unused, 62 | } 63 | 64 | // Values [1, MAX-1] represent the number of `Ref` active 65 | // (will not outgrow its range since `usize` is the size of the address space) 66 | struct BorrowFlag { 67 | flag: Cell, 68 | 69 | #[cfg(debug_assertions)] 70 | locations: StdRefCell>, 71 | } 72 | 73 | const UNUSED: usize = 0; 74 | const WRITING: usize = !0; 75 | 76 | impl RefCell { 77 | /// Creates a new `RefCell` containing `value`. 78 | pub fn new(value: T) -> RefCell { 79 | RefCell { 80 | borrow: BorrowFlag::new(), 81 | value: UnsafeCell::new(value), 82 | } 83 | } 84 | 85 | /// Consumes the `RefCell`, returning the wrapped value. 86 | pub fn into_inner(self) -> T { 87 | debug_assert!(self.borrow.flag.get() == UNUSED); 88 | unsafe { self.value.into_inner() } 89 | } 90 | } 91 | 92 | impl RefCell { 93 | /// Immutably borrows the wrapped value. 94 | /// 95 | /// The borrow lasts until the returned `Ref` exits scope. Multiple 96 | /// immutable borrows can be taken out at the same time. 97 | /// 98 | /// # Panics 99 | /// 100 | /// Panics if the value is currently mutably borrowed. 101 | #[cfg_attr(debug_assertions, inline(never))] 102 | pub fn borrow<'a>(&'a self) -> Ref<'a, T> { 103 | match BorrowRef::new(&self.borrow) { 104 | Some(b) => Ref { 105 | _value: unsafe { &*self.value.get() }, 106 | _borrow: b, 107 | }, 108 | None => self.panic("mutably borrowed"), 109 | } 110 | } 111 | 112 | /// Mutably borrows the wrapped value. 113 | /// 114 | /// The borrow lasts until the returned `RefMut` exits scope. The value 115 | /// cannot be borrowed while this borrow is active. 116 | /// 117 | /// # Panics 118 | /// 119 | /// Panics if the value is currently borrowed. 120 | #[cfg_attr(debug_assertions, inline(never))] 121 | pub fn borrow_mut<'a>(&'a self) -> RefMut<'a, T> { 122 | match BorrowRefMut::new(&self.borrow) { 123 | Some(b) => RefMut { 124 | _value: unsafe { &mut *self.value.get() }, 125 | _borrow: b, 126 | }, 127 | None => self.panic("borrowed"), 128 | } 129 | } 130 | 131 | #[cfg(not(debug_assertions))] 132 | fn panic(&self, msg: &str) -> ! { 133 | panic!("RefCell already {}", msg) 134 | } 135 | 136 | #[cfg(debug_assertions)] 137 | #[allow(unused_must_use)] 138 | fn panic(&self, msg: &str) -> ! { 139 | let mut msg = format!("RefCell already {}", msg); 140 | let locations = self.borrow.locations.borrow(); 141 | if locations.len() > 0 { 142 | msg.push_str("\ncurrent active borrows: \n"); 143 | for b in locations.iter() { 144 | msg.push_str(&format!("-------------------------\n{:?}\n", b)); 145 | } 146 | msg.push_str("\n\n"); 147 | } 148 | panic!(msg) 149 | } 150 | } 151 | 152 | #[cfg(not(debug_assertions))] 153 | impl BorrowFlag { 154 | #[inline] 155 | fn new() -> BorrowFlag { 156 | BorrowFlag { flag: Cell::new(UNUSED) } 157 | } 158 | 159 | #[inline] 160 | fn push(&self, _caller: Location) {} 161 | 162 | #[inline] 163 | fn pop(&self) {} 164 | } 165 | 166 | #[cfg(debug_assertions)] 167 | impl BorrowFlag { 168 | fn new() -> BorrowFlag { 169 | BorrowFlag { 170 | flag: Cell::new(UNUSED), 171 | locations: StdRefCell::new(Vec::new()), 172 | } 173 | } 174 | 175 | fn push(&self, caller: Location) { 176 | self.locations.borrow_mut().push(caller); 177 | } 178 | 179 | fn pop(&self) { 180 | self.locations.borrow_mut().pop(); 181 | } 182 | } 183 | 184 | #[cfg(not(debug_assertions))] 185 | #[inline] 186 | fn get_caller() -> Location {} 187 | 188 | #[inline(never)] 189 | #[cfg(debug_assertions)] 190 | fn get_caller() -> Location { 191 | backtrace::Backtrace::new() 192 | } 193 | 194 | unsafe impl Send for RefCell where T: Send {} 195 | 196 | impl Clone for RefCell { 197 | #[inline] 198 | fn clone(&self) -> RefCell { 199 | RefCell::new(self.borrow().clone()) 200 | } 201 | } 202 | 203 | impl Default for RefCell { 204 | #[inline] 205 | fn default() -> RefCell { 206 | RefCell::new(Default::default()) 207 | } 208 | } 209 | 210 | 211 | impl PartialEq for RefCell { 212 | #[inline] 213 | fn eq(&self, other: &RefCell) -> bool { 214 | *self.borrow() == *other.borrow() 215 | } 216 | } 217 | 218 | impl Eq for RefCell {} 219 | 220 | struct BorrowRef<'b> { 221 | borrow: &'b BorrowFlag, 222 | } 223 | 224 | impl<'b> BorrowRef<'b> { 225 | #[cfg_attr(debug_assertions, inline(never))] 226 | #[cfg_attr(not(debug_assertions), inline)] 227 | fn new(borrow: &'b BorrowFlag) -> Option> { 228 | let flag = borrow.flag.get(); 229 | if flag == WRITING { return None } 230 | borrow.flag.set(flag + 1); 231 | borrow.push(get_caller()); 232 | Some(BorrowRef { borrow: borrow }) 233 | } 234 | } 235 | 236 | impl<'b> Drop for BorrowRef<'b> { 237 | #[inline] 238 | fn drop(&mut self) { 239 | let flag = self.borrow.flag.get(); 240 | debug_assert!(flag != WRITING && flag != UNUSED); 241 | self.borrow.flag.set(flag - 1); 242 | self.borrow.pop(); 243 | } 244 | } 245 | 246 | /// Wraps a borrowed reference to a value in a `RefCell` box. 247 | /// A wrapper type for an immutably borrowed value from a `RefCell`. 248 | /// 249 | /// See the [module-level documentation](index.html) for more. 250 | 251 | pub struct Ref<'b, T: ?Sized + 'b> { 252 | // FIXME #12808: strange name to try to avoid interfering with 253 | // field accesses of the contained type via Deref 254 | _value: &'b T, 255 | _borrow: BorrowRef<'b>, 256 | } 257 | 258 | 259 | impl<'b, T: ?Sized> Deref for Ref<'b, T> { 260 | type Target = T; 261 | fn deref(&self) -> &T { 262 | self._value 263 | } 264 | } 265 | 266 | struct BorrowRefMut<'b> { 267 | borrow: &'b BorrowFlag, 268 | } 269 | 270 | impl<'b> BorrowRefMut<'b> { 271 | #[cfg_attr(debug_assertions, inline(never))] 272 | #[cfg_attr(not(debug_assertions), inline)] 273 | fn new(borrow: &'b BorrowFlag) -> Option> { 274 | if borrow.flag.get() != UNUSED { return None } 275 | borrow.flag.set(WRITING); 276 | borrow.push(get_caller()); 277 | Some(BorrowRefMut { borrow: borrow }) 278 | } 279 | } 280 | 281 | impl<'b> Drop for BorrowRefMut<'b> { 282 | #[inline] 283 | fn drop(&mut self) { 284 | debug_assert!(self.borrow.flag.get() == WRITING); 285 | self.borrow.flag.set(UNUSED); 286 | self.borrow.pop(); 287 | } 288 | } 289 | 290 | /// A wrapper type for a mutably borrowed value from a `RefCell`. 291 | pub struct RefMut<'b, T: ?Sized + 'b> { 292 | // FIXME #12808: strange name to try to avoid interfering with 293 | // field accesses of the contained type via Deref 294 | _value: &'b mut T, 295 | _borrow: BorrowRefMut<'b>, 296 | } 297 | 298 | 299 | impl<'b, T: ?Sized> Deref for RefMut<'b, T> { 300 | type Target = T; 301 | fn deref(&self) -> &T { 302 | self._value 303 | } 304 | } 305 | 306 | impl<'b, T: ?Sized> DerefMut for RefMut<'b, T> { 307 | fn deref_mut(&mut self) -> &mut T { 308 | self._value 309 | } 310 | } 311 | 312 | #[cfg(test)] 313 | mod tests { 314 | use super::RefCell; 315 | 316 | #[test] 317 | fn ok_borrows() { 318 | let a = RefCell::new(2); 319 | let b = a.borrow(); 320 | let c = a.borrow(); 321 | assert_eq!(*b, 2); 322 | assert_eq!(*c, 2); 323 | drop((b, c)); 324 | 325 | let mut b = a.borrow_mut(); 326 | assert_eq!(*b, 2); 327 | *b = 4; 328 | drop(b); 329 | 330 | assert_eq!(*a.borrow(), 4); 331 | } 332 | 333 | #[should_panic] 334 | #[test] 335 | fn bad_borrow_mut() { 336 | let a = RefCell::new(2); 337 | let _a = a.borrow(); 338 | a.borrow_mut(); 339 | } 340 | 341 | #[should_panic] 342 | #[test] 343 | fn bad_borrow() { 344 | let a = RefCell::new(2); 345 | let _a = a.borrow_mut(); 346 | a.borrow(); 347 | } 348 | } 349 | -------------------------------------------------------------------------------- /tests/smoke.rs: -------------------------------------------------------------------------------- 1 | extern crate debug_cell; 2 | 3 | use std::process::Command; 4 | use std::env; 5 | use debug_cell::RefCell; 6 | 7 | fn main() { 8 | let args = env::args().collect::>(); 9 | if args.len() > 1 && args[1] == "child1" { 10 | let r = RefCell::new(3); 11 | let _a = r.borrow(); 12 | let _b = r.borrow(); 13 | r.borrow_mut(); 14 | } else if args.len() > 1 && args[1] == "child2" { 15 | let r = RefCell::new(3); 16 | let _a = r.borrow_mut(); 17 | r.borrow_mut(); 18 | } else { 19 | runtest("child1", &[ 20 | "current active borrow", 21 | "tests/smoke.rs:11", 22 | "tests/smoke.rs:12", 23 | ]); 24 | runtest("child2", &[ 25 | "current active borrow", 26 | "tests/smoke.rs:16", 27 | ]); 28 | } 29 | } 30 | 31 | fn runtest(name: &str, substrs: &[&str]) { 32 | let output = Command::new(env::current_exe().unwrap()) 33 | .arg(name).output().unwrap(); 34 | let stderr = String::from_utf8(output.stderr).unwrap(); 35 | 36 | for s in substrs { 37 | assert!(stderr.contains(s) == cfg!(debug_assertions), 38 | "`{}` not found in `{}`", s, stderr); 39 | } 40 | println!("ok: {}", name); 41 | } 42 | --------------------------------------------------------------------------------