Auto merge of rust-lang#71258 - Mark-Simulacrum:beta-next, r=Mark-Sim…

…ulacrum

[beta] backports

This includes:
* Do not reuse post LTO products when exports change rust-lang#71131
* macro_rules: `NtLifetime` cannot start with an identifier rust-lang#70768
* Update RELEASES.md for 1.43.0 rust-lang#70354

r? @ghost

RELEASES.md

@@ -1,3 +1,152 @@
+Version 1.43.0 (2020-04-23)
+==========================
+
+Language
+--------
+- [Fixed using binary operations with `&{number}` (e.g. `&1.0`) not having
+  the type inferred correctly.][68129]
+- [Attributes such as `#[cfg()]` can now be used on `if` expressions.][69201]
+
+**Syntax only changes**
+- [Allow `type Foo: Ord` syntactically.][69361]
+- [Fuse associated and extern items up to defaultness.][69194]
+- [Syntactically allow `self` in all `fn` contexts.][68764]
+- [Merge `fn` syntax + cleanup item parsing.][68728]
+- [`item` macro fragments can be interpolated into `trait`s, `impl`s, and `extern` blocks.][69366]
+  For example, you may now write:
+  ```rust 
+  macro_rules! mac_trait {
+      ($i:item) => {
+          trait T { $i }
+      }
+  }
+  mac_trait! {
+      fn foo() {}
+  }
+  ```
+
+These are still rejected *semantically*, so you will likely receive an error but
+these changes can be seen and parsed by macros and
+conditional compilation.
+
+
+Compiler
+--------
+- [You can now pass multiple lint flags to rustc to override the previous
+  flags.][67885] For example; `rustc -D unused -A unused-variables` denies
+  everything in the `unused` lint group except `unused-variables` which
+  is explicitly allowed. However, passing `rustc -A unused-variables -D unused` denies
+  everything in the `unused` lint group **including** `unused-variables` since
+  the allow flag is specified before the deny flag (and therefore overridden).
+- [rustc will now prefer your system MinGW libraries over its bundled libraries
+  if they are available on `windows-gnu`.][67429]
+- [rustc now buffers errors/warnings printed in JSON.][69227]
+
+Libraries
+---------
+- [`Arc<[T; N]>`, `Box<[T; N]>`, and `Rc<[T; N]>`, now implement
+  `TryFrom<Arc<[T]>>`,`TryFrom<Box<[T]>>`, and `TryFrom<Rc<[T]>>`
+  respectively.][69538] **Note** These conversions are only available when `N`
+  is `0..=32`.
+- [You can now use associated constants on floats and integers directly, rather
+  than having to import the module.][68952] e.g. You can now write `u32::MAX` or
+  `f32::NAN` with no imports.
+- [`u8::is_ascii` is now `const`.][68984]
+- [`String` now implements `AsMut<str>`.][68742]
+- [Added the `primitive` module to `std` and `core`.][67637] This module
+  reexports Rust's primitive types. This is mainly useful in macros
+  where you want avoid these types being shadowed.
+- [Relaxed some of the trait bounds on `HashMap` and `HashSet`.][67642]
+- [`string::FromUtf8Error` now implements `Clone + Eq`.][68738]
+
+Stabilized APIs
+---------------
+- [`Once::is_completed`]
+- [`f32::LOG10_2`]
+- [`f32::LOG2_10`]
+- [`f64::LOG10_2`]
+- [`f64::LOG2_10`]
+- [`iter::once_with`]
+
+Cargo
+-----
+- [You can now set config `[profile]`s in your `.cargo/config`, or through
+  your environment.][cargo/7823]
+- [Cargo will now set `CARGO_BIN_EXE_<name>` pointing to a binary's
+  executable path when running integration tests or benchmarks.][cargo/7697]
+  `<name>` is the name of your binary as-is e.g. If you wanted the executable
+  path for a binary named `my-program`you would use `env!("CARGO_BIN_EXE_my-program")`.
+
+Misc
+----
+- [Certain checks in the `const_err` lint were deemed unrelated to const
+  evaluation][69185], and have been moved to the `unconditional_panic` and
+  `arithmetic_overflow` lints.
+
+Compatibility Notes
+-------------------
+
+- [Having trailing syntax in the `assert!` macro is now a hard error.][69548] This
+  has been a warning since 1.36.0.
+- [Fixed `Self` not having the correctly inferred type.][69340] This incorrectly
+  led to some instances being accepted, and now correctly emits a hard error.
+
+[69340]: https://github.com/rust-lang/rust/pull/69340
+
+Internal Only
+-------------
+These changes provide no direct user facing benefits, but represent significant
+improvements to the internals and overall performance of `rustc` and
+related tools.
+
+- [All components are now built with `opt-level=3` instead of `2`.][67878]
+- [Improved how rustc generates drop code.][67332]
+- [Improved performance from `#[inline]`-ing certain hot functions.][69256]
+- [traits: preallocate 2 Vecs of known initial size][69022]
+- [Avoid exponential behaviour when relating types][68772]
+- [Skip `Drop` terminators for enum variants without drop glue][68943]
+- [Improve performance of coherence checks][68966]
+- [Deduplicate types in the generator witness][68672]
+- [Invert control in struct_lint_level.][68725]
+
+[67332]: https://github.com/rust-lang/rust/pull/67332/
+[67429]: https://github.com/rust-lang/rust/pull/67429/
+[67637]: https://github.com/rust-lang/rust/pull/67637/
+[67642]: https://github.com/rust-lang/rust/pull/67642/
+[67878]: https://github.com/rust-lang/rust/pull/67878/
+[67885]: https://github.com/rust-lang/rust/pull/67885/
+[68129]: https://github.com/rust-lang/rust/pull/68129/
+[68672]: https://github.com/rust-lang/rust/pull/68672/
+[68725]: https://github.com/rust-lang/rust/pull/68725/
+[68728]: https://github.com/rust-lang/rust/pull/68728/
+[68738]: https://github.com/rust-lang/rust/pull/68738/
+[68742]: https://github.com/rust-lang/rust/pull/68742/
+[68764]: https://github.com/rust-lang/rust/pull/68764/
+[68772]: https://github.com/rust-lang/rust/pull/68772/
+[68943]: https://github.com/rust-lang/rust/pull/68943/
+[68952]: https://github.com/rust-lang/rust/pull/68952/
+[68966]: https://github.com/rust-lang/rust/pull/68966/
+[68984]: https://github.com/rust-lang/rust/pull/68984/
+[69022]: https://github.com/rust-lang/rust/pull/69022/
+[69185]: https://github.com/rust-lang/rust/pull/69185/
+[69194]: https://github.com/rust-lang/rust/pull/69194/
+[69201]: https://github.com/rust-lang/rust/pull/69201/
+[69227]: https://github.com/rust-lang/rust/pull/69227/
+[69548]: https://github.com/rust-lang/rust/pull/69548/
+[69256]: https://github.com/rust-lang/rust/pull/69256/
+[69361]: https://github.com/rust-lang/rust/pull/69361/
+[69366]: https://github.com/rust-lang/rust/pull/69366/
+[69538]: https://github.com/rust-lang/rust/pull/69538/
+[cargo/7823]: https://github.com/rust-lang/cargo/pull/7823
+[cargo/7697]: https://github.com/rust-lang/cargo/pull/7697
+[`Once::is_completed`]: https://doc.rust-lang.org/std/sync/struct.Once.html#method.is_completed
+[`f32::LOG10_2`]: https://doc.rust-lang.org/std/f32/consts/constant.LOG10_2.html
+[`f32::LOG2_10`]: https://doc.rust-lang.org/std/f32/consts/constant.LOG2_10.html
+[`f64::LOG10_2`]: https://doc.rust-lang.org/std/f64/consts/constant.LOG10_2.html
+[`f64::LOG2_10`]: https://doc.rust-lang.org/std/f64/consts/constant.LOG2_10.html
+[`iter::once_with`]: https://doc.rust-lang.org/std/iter/fn.once_with.html
+
+
 Version 1.42.0 (2020-03-12)
 ==========================
 
@@ -4838,7 +4987,6 @@ Version 1.11.0 (2016-08-18)
 Language
 --------
 
-* [`cfg_attr` works on `path` attributes](https://github.com/rust-lang/rust/pull/34546)
 * [Support nested `cfg_attr` attributes](https://github.com/rust-lang/rust/pull/34216)
 * [Allow statement-generating braced macro invocations at the end of blocks](https://github.com/rust-lang/rust/pull/34436)
 * [Macros can be expanded inside of trait definitions](https://github.com/rust-lang/rust/pull/34213)
@@ -4957,8 +5105,6 @@ Version 1.10.0 (2016-07-07)
 Language
 --------
 
-* [Allow `concat_idents!` in type positions as well as in expression
-  positions](https://github.com/rust-lang/rust/pull/33735).
 * [`Copy` types are required to have a trivial implementation of `Clone`](https://github.com/rust-lang/rust/pull/33420).
   [RFC 1521](https://github.com/rust-lang/rfcs/blob/master/text/1521-copy-clone-semantics.md).
 * [Single-variant enums support the `#[repr(..)]` attribute](https://github.com/rust-lang/rust/pull/33355).

src/librustc_codegen_llvm/back/lto.rs

@@ -463,15 +463,18 @@ fn thin_lto(
                 // If previous imports have been deleted, or we get an IO error
                 // reading the file storing them, then we'll just use `None` as the
                 // prev_import_map, which will force the code to be recompiled.
-                let prev =
-                    if path.exists() { ThinLTOImports::load_from_file(&path).ok() } else { None };
-                let curr = ThinLTOImports::from_thin_lto_data(data);
+                let prev = if path.exists() {
+                    ThinLTOImportMaps::load_from_file(&path).ok()
+                } else {
+                    None
+                };
+                let curr = ThinLTOImportMaps::from_thin_lto_data(data);
                 (Some(path), prev, curr)
             } else {
                 // If we don't compile incrementally, we don't need to load the
                 // import data from LLVM.
                 assert!(green_modules.is_empty());
-                let curr = ThinLTOImports::default();
+                let curr = ThinLTOImportMaps::default();
                 (None, None, curr)
             };
         info!("thin LTO import map loaded");
@@ -497,10 +500,14 @@ fn thin_lto(
             let module_name = module_name_to_str(module_name);
 
             // If (1.) the module hasn't changed, and (2.) none of the modules
-            // it imports from has changed, *and* (3.) the import-set itself has
-            // not changed from the previous compile when it was last
-            // ThinLTO'ed, then we can re-use the post-ThinLTO version of the
-            // module. Otherwise, freshly perform LTO optimization.
+            // it imports from nor exports to have changed, *and* (3.) the
+            // import and export sets themselves have not changed from the
+            // previous compile when it was last ThinLTO'ed, then we can re-use
+            // the post-ThinLTO version of the module. Otherwise, freshly
+            // perform LTO optimization.
+            //
+            // (Note that globally, the export set is just the inverse of the
+            // import set.)
             //
             // This strategy means we can always save the computed imports as
             // canon: when we reuse the post-ThinLTO version, condition (3.)
@@ -509,19 +516,30 @@ fn thin_lto(
             // version, the current import set *is* the correct one, since we
             // are doing the ThinLTO in this current compilation cycle.)
             //
-            // See rust-lang/rust#59535.
+            // For more discussion, see rust-lang/rust#59535 (where the import
+            // issue was discovered) and rust-lang/rust#69798 (where the
+            // analogous export issue was discovered).
             if let (Some(prev_import_map), true) =
                 (prev_import_map.as_ref(), green_modules.contains_key(module_name))
             {
                 assert!(cgcx.incr_comp_session_dir.is_some());
 
-                let prev_imports = prev_import_map.modules_imported_by(module_name);
-                let curr_imports = curr_import_map.modules_imported_by(module_name);
+                let prev_imports = prev_import_map.imports_of(module_name);
+                let curr_imports = curr_import_map.imports_of(module_name);
+                let prev_exports = prev_import_map.exports_of(module_name);
+                let curr_exports = curr_import_map.exports_of(module_name);
                 let imports_all_green = curr_imports
                     .iter()
                     .all(|imported_module| green_modules.contains_key(imported_module));
+                let exports_all_green = curr_exports
+                    .iter()
+                    .all(|exported_module| green_modules.contains_key(exported_module));
 
-                if imports_all_green && equivalent_as_sets(prev_imports, curr_imports) {
+                if imports_all_green
+                    && equivalent_as_sets(prev_imports, curr_imports)
+                    && exports_all_green
+                    && equivalent_as_sets(prev_exports, curr_exports)
+                {
                     let work_product = green_modules[module_name].clone();
                     copy_jobs.push(work_product);
                     info!(" - {}: re-used", module_name);
@@ -881,17 +899,32 @@ pub unsafe fn optimize_thin_module(
     Ok(module)
 }
 
+/// Summarizes module import/export relationships used by LLVM's ThinLTO pass.
+///
+/// Note that we tend to have two such instances of `ThinLTOImportMaps` in use:
+/// one loaded from a file that represents the relationships used during the
+/// compilation associated with the incremetnal build artifacts we are
+/// attempting to reuse, and another constructed via `from_thin_lto_data`, which
+/// captures the relationships of ThinLTO in the current compilation.
 #[derive(Debug, Default)]
-pub struct ThinLTOImports {
+pub struct ThinLTOImportMaps {
     // key = llvm name of importing module, value = list of modules it imports from
     imports: FxHashMap<String, Vec<String>>,
+    // key = llvm name of exporting module, value = list of modules it exports to
+    exports: FxHashMap<String, Vec<String>>,
 }
 
-impl ThinLTOImports {
-    fn modules_imported_by(&self, llvm_module_name: &str) -> &[String] {
+impl ThinLTOImportMaps {
+    /// Returns modules imported by `llvm_module_name` during some ThinLTO pass.
+    fn imports_of(&self, llvm_module_name: &str) -> &[String] {
         self.imports.get(llvm_module_name).map(|v| &v[..]).unwrap_or(&[])
     }
 
+    /// Returns modules exported by `llvm_module_name` during some ThinLTO pass.
+    fn exports_of(&self, llvm_module_name: &str) -> &[String] {
+        self.exports.get(llvm_module_name).map(|v| &v[..]).unwrap_or(&[])
+    }
+
     fn save_to_file(&self, path: &Path) -> io::Result<()> {
         use std::io::Write;
         let file = File::create(path)?;
@@ -906,16 +939,20 @@ impl ThinLTOImports {
         Ok(())
     }
 
-    fn load_from_file(path: &Path) -> io::Result<ThinLTOImports> {
+    fn load_from_file(path: &Path) -> io::Result<ThinLTOImportMaps> {
         use std::io::BufRead;
         let mut imports = FxHashMap::default();
-        let mut current_module = None;
-        let mut current_imports = vec![];
+        let mut exports: FxHashMap<_, Vec<_>> = FxHashMap::default();
+        let mut current_module: Option<String> = None;
+        let mut current_imports: Vec<String> = vec![];
         let file = File::open(path)?;
         for line in io::BufReader::new(file).lines() {
             let line = line?;
             if line.is_empty() {
                 let importing_module = current_module.take().expect("Importing module not set");
+                for imported in &current_imports {
+                    exports.entry(imported.clone()).or_default().push(importing_module.clone());
+                }
                 imports.insert(importing_module, mem::replace(&mut current_imports, vec![]));
             } else if line.starts_with(' ') {
                 // Space marks an imported module
@@ -927,17 +964,17 @@ impl ThinLTOImports {
                 current_module = Some(line.trim().to_string());
             }
         }
-        Ok(ThinLTOImports { imports })
+        Ok(ThinLTOImportMaps { imports, exports })
     }
 
     /// Loads the ThinLTO import map from ThinLTOData.
-    unsafe fn from_thin_lto_data(data: *const llvm::ThinLTOData) -> ThinLTOImports {
+    unsafe fn from_thin_lto_data(data: *const llvm::ThinLTOData) -> ThinLTOImportMaps {
         unsafe extern "C" fn imported_module_callback(
             payload: *mut libc::c_void,
             importing_module_name: *const libc::c_char,
             imported_module_name: *const libc::c_char,
         ) {
-            let map = &mut *(payload as *mut ThinLTOImports);
+            let map = &mut *(payload as *mut ThinLTOImportMaps);
             let importing_module_name = CStr::from_ptr(importing_module_name);
             let importing_module_name = module_name_to_str(&importing_module_name);
             let imported_module_name = CStr::from_ptr(imported_module_name);
@@ -951,8 +988,18 @@ impl ThinLTOImports {
                 .get_mut(importing_module_name)
                 .unwrap()
                 .push(imported_module_name.to_owned());
+
+            if !map.exports.contains_key(imported_module_name) {
+                map.exports.insert(imported_module_name.to_owned(), vec![]);
+            }
+
+            map.exports
+                .get_mut(imported_module_name)
+                .unwrap()
+                .push(importing_module_name.to_owned());
         }
-        let mut map = ThinLTOImports::default();
+
+        let mut map = ThinLTOImportMaps::default();
         llvm::LLVMRustGetThinLTOModuleImports(
             data,
             imported_module_callback,

src/librustc_expand/mbe/macro_parser.rs

@@ -762,7 +762,7 @@ fn may_begin_with(token: &Token, name: Name) -> bool {
     /// Checks whether the non-terminal may contain a single (non-keyword) identifier.
     fn may_be_ident(nt: &token::Nonterminal) -> bool {
         match *nt {
-            token::NtItem(_) | token::NtBlock(_) | token::NtVis(_) => false,
+            token::NtItem(_) | token::NtBlock(_) | token::NtVis(_) | token::NtLifetime(_) => false,
             _ => true,
         }
     }

src/test/incremental/thinlto/cgu_invalidated_when_export_added.rs

@@ -0,0 +1,26 @@
+// revisions: cfail1 cfail2
+// build-pass
+
+// rust-lang/rust#69798:
+//
+// This is analgous to cgu_invalidated_when_import_added, but it covers a
+// problem uncovered where a change to the *export* set caused a link failure
+// when reusing post-LTO optimized object code.
+
+pub struct Foo {}
+impl Drop for Foo {
+    fn drop(&mut self) {
+        println!("Dropping Foo");
+    }
+}
+#[no_mangle]
+pub extern "C" fn run() {
+    thread_local! { pub static FOO : Foo = Foo { } ; }
+
+    #[cfg(cfail2)]
+    {
+        FOO.with(|_f| ())
+    }
+}
+
+pub fn main() { run() }