Rollup of 8 pull requests

Cargo.lock

@@ -3746,6 +3746,7 @@ dependencies = [
  "rustc_errors",
  "rustc_feature",
  "rustc_lexer",
+ "rustc_lint_defs",
  "rustc_macros",
  "rustc_parse",
  "rustc_serialize",

compiler/rustc_ast_lowering/src/item.rs

@@ -319,10 +319,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
             ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
             ItemKind::ForeignMod(ref fm) => {
                 if fm.abi.is_none() {
-                    self.maybe_lint_missing_abi(span, id, abi::Abi::C);
+                    self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
                 }
                 hir::ItemKind::ForeignMod {
-                    abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
+                    abi: fm.abi.map_or(abi::Abi::C { unwind: false }, |abi| self.lower_abi(abi)),
                     items: self
                         .arena
                         .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
@@ -1315,8 +1315,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         match ext {
             Extern::None => abi::Abi::Rust,
             Extern::Implicit => {
-                self.maybe_lint_missing_abi(span, id, abi::Abi::C);
-                abi::Abi::C
+                self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
+                abi::Abi::C { unwind: false }
             }
             Extern::Explicit(abi) => self.lower_abi(abi),
         }

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -156,6 +156,39 @@ impl<'a> PostExpansionVisitor<'a> {
                     "efiapi ABI is experimental and subject to change"
                 );
             }
+            // FFI Unwinding ABI's
+            "C-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "C-unwind ABI is experimental and subject to change"
+                );
+            }
+            "stdcall-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "stdcall-unwind ABI is experimental and subject to change"
+                );
+            }
+            "system-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "system-unwind ABI is experimental and subject to change"
+                );
+            }
+            "thiscall-unwind" => {
+                gate_feature_post!(
+                    &self,
+                    c_unwind,
+                    span,
+                    "thiscall-unwind ABI is experimental and subject to change"
+                );
+            }
             abi => self
                 .sess
                 .parse_sess

compiler/rustc_codegen_cranelift/src/abi/mod.rs

@@ -101,7 +101,7 @@ fn clif_sig_from_fn_sig<'tcx>(
     requires_caller_location: bool,
 ) -> Signature {
     let abi = match sig.abi {
-        Abi::System => Abi::C,
+        Abi::System { unwind: false } => Abi::C { unwind: false },
         abi => abi,
     };
     let (call_conv, inputs, output): (CallConv, Vec<Ty<'tcx>>, Ty<'tcx>) = match abi {
@@ -110,7 +110,7 @@ fn clif_sig_from_fn_sig<'tcx>(
             sig.inputs().to_vec(),
             sig.output(),
         ),
-        Abi::C | Abi::Unadjusted => (
+        Abi::C { unwind: false } | Abi::Unadjusted => (
             CallConv::triple_default(triple),
             sig.inputs().to_vec(),
             sig.output(),
@@ -126,7 +126,7 @@ fn clif_sig_from_fn_sig<'tcx>(
             inputs.extend(extra_args.types());
             (CallConv::triple_default(triple), inputs, sig.output())
         }
-        Abi::System => unreachable!(),
+        Abi::System { .. } => unreachable!(),
         Abi::RustIntrinsic => (
             CallConv::triple_default(triple),
             sig.inputs().to_vec(),
@@ -664,7 +664,7 @@ pub(crate) fn codegen_terminator_call<'tcx>(
 
     // FIXME find a cleaner way to support varargs
     if fn_sig.c_variadic {
-        if fn_sig.abi != Abi::C {
+        if !matches!(fn_sig.abi, Abi::C { .. }) {
             fx.tcx.sess.span_fatal(
                 span,
                 &format!("Variadic call for non-C abi {:?}", fn_sig.abi),

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2211,8 +2211,13 @@ fn add_apple_sdk(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
             return;
         }
     };
-    let arch_name = llvm_target.split('-').next().expect("LLVM target must have a hyphen");
-    cmd.args(&["-arch", arch_name, "-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
+    if llvm_target.contains("macabi") {
+        cmd.args(&["-target", llvm_target])
+    } else {
+        let arch_name = llvm_target.split('-').next().expect("LLVM target must have a hyphen");
+        cmd.args(&["-arch", arch_name])
+    }
+    cmd.args(&["-isysroot", &sdk_root, "-Wl,-syslibroot", &sdk_root]);
 }
 
 fn get_apple_sdk_root(sdk_name: &str) -> Result<String, String> {

compiler/rustc_expand/Cargo.toml

@@ -18,6 +18,7 @@ rustc_attr = { path = "../rustc_attr" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
 rustc_feature = { path = "../rustc_feature" }
+rustc_lint_defs = { path = "../rustc_lint_defs" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_parse = { path = "../rustc_parse" }

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -11,12 +11,14 @@ use crate::mbe::transcribe::transcribe;
 use rustc_ast as ast;
 use rustc_ast::token::{self, NonterminalKind, NtTT, Token, TokenKind::*};
 use rustc_ast::tokenstream::{DelimSpan, TokenStream};
+use rustc_ast::NodeId;
 use rustc_ast_pretty::pprust;
 use rustc_attr::{self as attr, TransparencyError};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_feature::Features;
+use rustc_lint_defs::builtin::SEMICOLON_IN_EXPRESSIONS_FROM_MACROS;
 use rustc_parse::parser::Parser;
 use rustc_session::parse::ParseSess;
 use rustc_session::Session;
@@ -37,6 +39,7 @@ crate struct ParserAnyMacro<'a> {
     site_span: Span,
     /// The ident of the macro we're parsing
     macro_ident: Ident,
+    lint_node_id: NodeId,
     arm_span: Span,
 }
 
@@ -110,7 +113,8 @@ fn emit_frag_parse_err(
 
 impl<'a> ParserAnyMacro<'a> {
     crate fn make(mut self: Box<ParserAnyMacro<'a>>, kind: AstFragmentKind) -> AstFragment {
-        let ParserAnyMacro { site_span, macro_ident, ref mut parser, arm_span } = *self;
+        let ParserAnyMacro { site_span, macro_ident, ref mut parser, lint_node_id, arm_span } =
+            *self;
         let snapshot = &mut parser.clone();
         let fragment = match parse_ast_fragment(parser, kind) {
             Ok(f) => f,
@@ -124,6 +128,12 @@ impl<'a> ParserAnyMacro<'a> {
         // `macro_rules! m { () => { panic!(); } }` isn't parsed by `.parse_expr()`,
         // but `m!()` is allowed in expression positions (cf. issue #34706).
         if kind == AstFragmentKind::Expr && parser.token == token::Semi {
+            parser.sess.buffer_lint(
+                SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
+                parser.token.span,
+                lint_node_id,
+                "trailing semicolon in macro used in expression position",
+            );
             parser.bump();
         }
 
@@ -276,6 +286,7 @@ fn generic_extension<'cx>(
 
                 let mut p = Parser::new(sess, tts, false, None);
                 p.last_type_ascription = cx.current_expansion.prior_type_ascription;
+                let lint_node_id = cx.resolver.lint_node_id(cx.current_expansion.id);
 
                 // Let the context choose how to interpret the result.
                 // Weird, but useful for X-macros.
@@ -287,6 +298,7 @@ fn generic_extension<'cx>(
                     // macro leaves unparsed tokens.
                     site_span: sp,
                     macro_ident: name,
+                    lint_node_id,
                     arm_span,
                 });
             }

compiler/rustc_feature/src/active.rs

@@ -631,6 +631,10 @@ declare_features! (
 
     /// Allows using `pointer` and `reference` in intra-doc links
     (active, intra_doc_pointers, "1.51.0", Some(80896), None),
+
+    /// Allows `extern "C-unwind" fn` to enable unwinding across ABI boundaries.
+    (active, c_unwind, "1.51.0", Some(74990), None),
+
     // -------------------------------------------------------------------------
     // feature-group-end: actual feature gates
     // -------------------------------------------------------------------------

compiler/rustc_lint/src/context.rs

@@ -746,6 +746,14 @@ impl<'tcx> LateContext<'tcx> {
             hir::QPath::Resolved(_, ref path) => path.res,
             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
                 .maybe_typeck_results()
+                .filter(|typeck_results| typeck_results.hir_owner == id.owner)
+                .or_else(|| {
+                    if self.tcx.has_typeck_results(id.owner.to_def_id()) {
+                        Some(self.tcx.typeck(id.owner))
+                    } else {
+                        None
+                    }
+                })
                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
         }

compiler/rustc_lint/src/late.rs

@@ -140,13 +140,17 @@ impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPas
     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
         let generics = self.context.generics.take();
         self.context.generics = it.kind.generics();
+        let old_cached_typeck_results = self.context.cached_typeck_results.take();
+        let old_enclosing_body = self.context.enclosing_body.take();
         self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
             cx.with_param_env(it.hir_id, |cx| {
                 lint_callback!(cx, check_item, it);
                 hir_visit::walk_item(cx, it);
                 lint_callback!(cx, check_item_post, it);
             });
         });
+        self.context.enclosing_body = old_enclosing_body;
+        self.context.cached_typeck_results.set(old_cached_typeck_results);
         self.context.generics = generics;
     }
 

compiler/rustc_lint_defs/src/builtin.rs

@@ -1,3 +1,4 @@
+// ignore-tidy-filelength
 //! Some lints that are built in to the compiler.
 //!
 //! These are the built-in lints that are emitted direct in the main
@@ -2833,6 +2834,52 @@ declare_lint! {
     "detects `#[unstable]` on stable trait implementations for stable types"
 }
 
+declare_lint! {
+    /// The `semicolon_in_expressions_from_macros` lint detects trailing semicolons
+    /// in macro bodies when the macro is invoked in expression position.
+    /// This was previous accepted, but is being phased out.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![deny(semicolon_in_expressions_from_macros)]
+    /// macro_rules! foo {
+    ///     () => { true; }
+    /// }
+    ///
+    /// fn main() {
+    ///     let val = match true {
+    ///         true => false,
+    ///         _ => foo!()
+    ///     };
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Previous, Rust ignored trailing semicolon in a macro
+    /// body when a macro was invoked in expression position.
+    /// However, this makes the treatment of semicolons in the language
+    /// inconsistent, and could lead to unexpected runtime behavior
+    /// in some circumstances (e.g. if the macro author expects
+    /// a value to be dropped).
+    ///
+    /// This is a [future-incompatible] lint to transition this
+    /// to a hard error in the future. See [issue #79813] for more details.
+    ///
+    /// [issue #79813]: https://github.com/rust-lang/rust/issues/79813
+    /// [future-incompatible]: ../index.md#future-incompatible-lints
+    pub SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
+    Allow,
+    "trailing semicolon in macro body used as expression",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #79813 <https://github.com/rust-lang/rust/issues/79813>",
+        edition: None,
+    };
+}
+
 declare_lint_pass! {
     /// Does nothing as a lint pass, but registers some `Lint`s
     /// that are used by other parts of the compiler.
@@ -2920,6 +2967,7 @@ declare_lint_pass! {
         USELESS_DEPRECATED,
         UNSUPPORTED_NAKED_FUNCTIONS,
         MISSING_ABI,
+        SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
     ]
 }
 

compiler/rustc_middle/src/ty/layout.rs

@@ -2546,6 +2546,7 @@ fn fn_can_unwind(
     panic_strategy: PanicStrategy,
     codegen_fn_attr_flags: CodegenFnAttrFlags,
     call_conv: Conv,
+    abi: SpecAbi,
 ) -> bool {
     if panic_strategy != PanicStrategy::Unwind {
         // In panic=abort mode we assume nothing can unwind anywhere, so
@@ -2570,17 +2571,33 @@ fn fn_can_unwind(
             //
             //  2. A Rust item using a non-Rust ABI (like `extern "C" fn foo() { ... }`).
             //
-            // Foreign items (case 1) are assumed to not unwind; it is
-            // UB otherwise. (At least for now; see also
-            // rust-lang/rust#63909 and Rust RFC 2753.)
-            //
-            // Items defined in Rust with non-Rust ABIs (case 2) are also
-            // not supposed to unwind. Whether this should be enforced
-            // (versus stating it is UB) and *how* it would be enforced
-            // is currently under discussion; see rust-lang/rust#58794.
-            //
-            // In either case, we mark item as explicitly nounwind.
-            false
+            // In both of these cases, we should refer to the ABI to determine whether or not we
+            // should unwind. See Rust RFC 2945 for more information on this behavior, here:
+            // https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
+            use SpecAbi::*;
+            match abi {
+                C { unwind } | Stdcall { unwind } | System { unwind } | Thiscall { unwind } => {
+                    unwind
+                }
+                Cdecl
+                | Fastcall
+                | Vectorcall
+                | Aapcs
+                | Win64
+                | SysV64
+                | PtxKernel
+                | Msp430Interrupt
+                | X86Interrupt
+                | AmdGpuKernel
+                | EfiApi
+                | AvrInterrupt
+                | AvrNonBlockingInterrupt
+                | RustIntrinsic
+                | PlatformIntrinsic
+                | Unadjusted => false,
+                // In the `if` above, we checked for functions with the Rust calling convention.
+                Rust | RustCall => unreachable!(),
+            }
         }
     }
 }
@@ -2638,14 +2655,14 @@ where
             RustIntrinsic | PlatformIntrinsic | Rust | RustCall => Conv::Rust,
 
             // It's the ABI's job to select this, not ours.
-            System => bug!("system abi should be selected elsewhere"),
+            System { .. } => bug!("system abi should be selected elsewhere"),
             EfiApi => bug!("eficall abi should be selected elsewhere"),
 
-            Stdcall => Conv::X86Stdcall,
+            Stdcall { .. } => Conv::X86Stdcall,
             Fastcall => Conv::X86Fastcall,
             Vectorcall => Conv::X86VectorCall,
-            Thiscall => Conv::X86ThisCall,
-            C => Conv::C,
+            Thiscall { .. } => Conv::X86ThisCall,
+            C { .. } => Conv::C,
             Unadjusted => Conv::C,
             Win64 => Conv::X86_64Win64,
             SysV64 => Conv::X86_64SysV,
@@ -2806,7 +2823,12 @@ where
             c_variadic: sig.c_variadic,
             fixed_count: inputs.len(),
             conv,
-            can_unwind: fn_can_unwind(cx.tcx().sess.panic_strategy(), codegen_fn_attr_flags, conv),
+            can_unwind: fn_can_unwind(
+                cx.tcx().sess.panic_strategy(),
+                codegen_fn_attr_flags,
+                conv,
+                sig.abi,
+            ),
         };
         fn_abi.adjust_for_abi(cx, sig.abi);
         debug!("FnAbi::new_internal = {:?}", fn_abi);