Rollup of 9 pull requests

compiler/rustc_abi/src/canon_abi.rs

@@ -28,6 +28,9 @@ pub enum CanonAbi {
     Rust,
     RustCold,
 
+    /// An ABI that rustc does not know how to call or define.
+    Custom,
+
     /// ABIs relevant to 32-bit Arm targets
     Arm(ArmCall),
     /// ABI relevant to GPUs: the entry point for a GPU kernel
@@ -57,6 +60,7 @@ impl fmt::Display for CanonAbi {
             CanonAbi::C => ExternAbi::C { unwind: false },
             CanonAbi::Rust => ExternAbi::Rust,
             CanonAbi::RustCold => ExternAbi::RustCold,
+            CanonAbi::Custom => ExternAbi::Custom,
             CanonAbi::Arm(arm_call) => match arm_call {
                 ArmCall::Aapcs => ExternAbi::Aapcs { unwind: false },
                 ArmCall::CCmseNonSecureCall => ExternAbi::CCmseNonSecureCall,

compiler/rustc_abi/src/extern_abi.rs

@@ -40,6 +40,11 @@ pub enum ExternAbi {
     /// Even normally-compatible Rust types can become ABI-incompatible with this ABI!
     Unadjusted,
 
+    /// An ABI that rustc does not know how to call or define. Functions with this ABI can
+    /// only be created using `#[naked]` functions or `extern "custom"` blocks, and can only
+    /// be called from inline assembly.
+    Custom,
+
     /// UEFI ABI, usually an alias of C, but sometimes an arch-specific alias
     /// and only valid on platforms that have a UEFI standard
     EfiApi,
@@ -141,6 +146,7 @@ abi_impls! {
             AvrNonBlockingInterrupt =><= "avr-non-blocking-interrupt",
             Cdecl { unwind: false } =><= "cdecl",
             Cdecl { unwind: true } =><= "cdecl-unwind",
+            Custom =><= "custom",
             EfiApi =><= "efiapi",
             Fastcall { unwind: false } =><= "fastcall",
             Fastcall { unwind: true } =><= "fastcall-unwind",

compiler/rustc_ast/src/ast.rs

@@ -3520,6 +3520,38 @@ impl FnHeader {
             || matches!(constness, Const::Yes(_))
             || !matches!(ext, Extern::None)
     }
+
+    /// Return a span encompassing the header, or none if all options are default.
+    pub fn span(&self) -> Option<Span> {
+        fn append(a: &mut Option<Span>, b: Span) {
+            *a = match a {
+                None => Some(b),
+                Some(x) => Some(x.to(b)),
+            }
+        }
+
+        let mut full_span = None;
+
+        match self.safety {
+            Safety::Unsafe(span) | Safety::Safe(span) => append(&mut full_span, span),
+            Safety::Default => {}
+        };
+
+        if let Some(coroutine_kind) = self.coroutine_kind {
+            append(&mut full_span, coroutine_kind.span());
+        }
+
+        if let Const::Yes(span) = self.constness {
+            append(&mut full_span, span);
+        }
+
+        match self.ext {
+            Extern::Implicit(span) | Extern::Explicit(_, span) => append(&mut full_span, span),
+            Extern::None => {}
+        }
+
+        full_span
+    }
 }
 
 impl Default for FnHeader {

compiler/rustc_ast_lowering/src/item.rs

@@ -63,7 +63,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
 
         for (def_id, info) in lctx.children {
             let owner = self.owners.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom);
-            debug_assert!(
+            assert!(
                 matches!(owner, hir::MaybeOwner::Phantom),
                 "duplicate copy of {def_id:?} in lctx.children"
             );
@@ -78,7 +78,7 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             match node {
                 AstOwner::NonOwner => {}
                 AstOwner::Crate(c) => {
-                    debug_assert_eq!(self.resolver.node_id_to_def_id[&CRATE_NODE_ID], CRATE_DEF_ID);
+                    assert_eq!(self.resolver.node_id_to_def_id[&CRATE_NODE_ID], CRATE_DEF_ID);
                     self.with_lctx(CRATE_NODE_ID, |lctx| {
                         let module = lctx.lower_mod(&c.items, &c.spans);
                         // FIXME(jdonszelman): is dummy span ever a problem here?
@@ -1160,7 +1160,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> hir::BodyId {
         let body = hir::Body { params, value: self.arena.alloc(value) };
         let id = body.id();
-        debug_assert_eq!(id.hir_id.owner, self.current_hir_id_owner);
+        assert_eq!(id.hir_id.owner, self.current_hir_id_owner);
         self.bodies.push((id.hir_id.local_id, self.arena.alloc(body)));
         id
     }
@@ -1673,8 +1673,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         itctx: ImplTraitContext,
         f: impl FnOnce(&mut Self) -> T,
     ) -> (&'hir hir::Generics<'hir>, T) {
-        debug_assert!(self.impl_trait_defs.is_empty());
-        debug_assert!(self.impl_trait_bounds.is_empty());
+        assert!(self.impl_trait_defs.is_empty());
+        assert!(self.impl_trait_bounds.is_empty());
 
         // Error if `?Trait` bounds in where clauses don't refer directly to type parameters.
         // Note: we used to clone these bounds directly onto the type parameter (and avoid lowering

compiler/rustc_ast_lowering/src/lib.rs

@@ -523,7 +523,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         span: Span,
     ) -> LocalDefId {
         let parent = self.current_hir_id_owner.def_id;
-        debug_assert_ne!(node_id, ast::DUMMY_NODE_ID);
+        assert_ne!(node_id, ast::DUMMY_NODE_ID);
         assert!(
             self.opt_local_def_id(node_id).is_none(),
             "adding a def'n for node-id {:?} and def kind {:?} but a previous def'n exists: {:?}",
@@ -607,10 +607,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
 
         let item = f(self);
-        debug_assert_eq!(owner_id, item.def_id());
+        assert_eq!(owner_id, item.def_id());
         // `f` should have consumed all the elements in these vectors when constructing `item`.
-        debug_assert!(self.impl_trait_defs.is_empty());
-        debug_assert!(self.impl_trait_bounds.is_empty());
+        assert!(self.impl_trait_defs.is_empty());
+        assert!(self.impl_trait_bounds.is_empty());
         let info = self.make_owner_info(item);
 
         self.attrs = current_attrs;
@@ -918,7 +918,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         } else {
             let lowered_attrs = self.lower_attrs_vec(attrs, self.lower_span(target_span), id);
 
-            debug_assert_eq!(id.owner, self.current_hir_id_owner);
+            assert_eq!(id.owner, self.current_hir_id_owner);
             let ret = self.arena.alloc_from_iter(lowered_attrs);
 
             // this is possible if an item contained syntactical attribute,
@@ -956,10 +956,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn alias_attrs(&mut self, id: HirId, target_id: HirId) {
-        debug_assert_eq!(id.owner, self.current_hir_id_owner);
-        debug_assert_eq!(target_id.owner, self.current_hir_id_owner);
+        assert_eq!(id.owner, self.current_hir_id_owner);
+        assert_eq!(target_id.owner, self.current_hir_id_owner);
         if let Some(&a) = self.attrs.get(&target_id.local_id) {
-            debug_assert!(!a.is_empty());
+            assert!(!a.is_empty());
             self.attrs.insert(id.local_id, a);
         }
     }
@@ -1438,7 +1438,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 let id = if let Some(LifetimeRes::ElidedAnchor { start, end }) =
                     self.resolver.get_lifetime_res(t.id)
                 {
-                    debug_assert_eq!(start.plus(1), end);
+                    assert_eq!(start.plus(1), end);
                     start
                 } else {
                     self.next_node_id()
@@ -1846,16 +1846,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let res = match res {
             LifetimeRes::Param { param, .. } => hir::LifetimeKind::Param(param),
             LifetimeRes::Fresh { param, .. } => {
-                debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
+                assert_eq!(ident.name, kw::UnderscoreLifetime);
                 let param = self.local_def_id(param);
                 hir::LifetimeKind::Param(param)
             }
             LifetimeRes::Infer => {
-                debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
+                assert_eq!(ident.name, kw::UnderscoreLifetime);
                 hir::LifetimeKind::Infer
             }
             LifetimeRes::Static { .. } => {
-                debug_assert!(matches!(ident.name, kw::StaticLifetime | kw::UnderscoreLifetime));
+                assert!(matches!(ident.name, kw::StaticLifetime | kw::UnderscoreLifetime));
                 hir::LifetimeKind::Static
             }
             LifetimeRes::Error => hir::LifetimeKind::Error,
@@ -2285,7 +2285,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     ) -> hir::Stmt<'hir> {
         let hir_id = self.next_id();
         if let Some(a) = attrs {
-            debug_assert!(!a.is_empty());
+            assert!(!a.is_empty());
             self.attrs.insert(hir_id.local_id, a);
         }
         let local = hir::LetStmt {

compiler/rustc_ast_lowering/src/stability.rs

@@ -134,5 +134,8 @@ pub fn extern_abi_stability(abi: ExternAbi) -> Result<(), UnstableAbi> {
             feature: sym::cmse_nonsecure_entry,
             explain: GateReason::Experimental,
         }),
+        ExternAbi::Custom => {
+            Err(UnstableAbi { abi, feature: sym::abi_custom, explain: GateReason::Experimental })
+        }
     }
 }

compiler/rustc_ast_passes/messages.ftl

@@ -1,3 +1,20 @@
+ast_passes_abi_custom_coroutine =
+    functions with the `"custom"` ABI cannot be `{$coroutine_kind_str}`
+    .suggestion = remove the `{$coroutine_kind_str}` keyword from this definiton
+
+ast_passes_abi_custom_invalid_signature =
+    invalid signature for `extern "custom"` function
+    .note = functions with the `"custom"` ABI cannot have any parameters or return type
+    .suggestion = remove the parameters and return type
+
+ast_passes_abi_custom_safe_foreign_function =
+    foreign functions with the `"custom"` ABI cannot be safe
+    .suggestion = remove the `safe` keyword from this definition
+
+ast_passes_abi_custom_safe_function =
+    functions with the `"custom"` ABI must be unsafe
+    .suggestion = add the `unsafe` keyword to this definition
+
 ast_passes_assoc_const_without_body =
     associated constant in `impl` without body
     .suggestion = provide a definition for the constant

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -18,6 +18,7 @@
 
 use std::mem;
 use std::ops::{Deref, DerefMut};
+use std::str::FromStr;
 
 use itertools::{Either, Itertools};
 use rustc_abi::ExternAbi;
@@ -81,6 +82,7 @@ struct AstValidator<'a> {
 
     /// Used to ban explicit safety on foreign items when the extern block is not marked as unsafe.
     extern_mod_safety: Option<Safety>,
+    extern_mod_abi: Option<ExternAbi>,
 
     lint_node_id: NodeId,
 
@@ -121,10 +123,17 @@ impl<'a> AstValidator<'a> {
         self.outer_trait_or_trait_impl = old;
     }
 
-    fn with_in_extern_mod(&mut self, extern_mod_safety: Safety, f: impl FnOnce(&mut Self)) {
-        let old = mem::replace(&mut self.extern_mod_safety, Some(extern_mod_safety));
+    fn with_in_extern_mod(
+        &mut self,
+        extern_mod_safety: Safety,
+        abi: Option<ExternAbi>,
+        f: impl FnOnce(&mut Self),
+    ) {
+        let old_safety = mem::replace(&mut self.extern_mod_safety, Some(extern_mod_safety));
+        let old_abi = mem::replace(&mut self.extern_mod_abi, abi);
         f(self);
-        self.extern_mod_safety = old;
+        self.extern_mod_safety = old_safety;
+        self.extern_mod_abi = old_abi;
     }
 
     fn with_tilde_const(
@@ -370,6 +379,65 @@ impl<'a> AstValidator<'a> {
         }
     }
 
+    /// An `extern "custom"` function must be unsafe, and must not have any parameters or return
+    /// type.
+    fn check_custom_abi(&self, ctxt: FnCtxt, ident: &Ident, sig: &FnSig) {
+        let dcx = self.dcx();
+
+        // An `extern "custom"` function must be unsafe.
+        match sig.header.safety {
+            Safety::Unsafe(_) => { /* all good */ }
+            Safety::Safe(safe_span) => {
+                let safe_span =
+                    self.sess.psess.source_map().span_until_non_whitespace(safe_span.to(sig.span));
+                dcx.emit_err(errors::AbiCustomSafeForeignFunction { span: sig.span, safe_span });
+            }
+            Safety::Default => match ctxt {
+                FnCtxt::Foreign => { /* all good */ }
+                FnCtxt::Free | FnCtxt::Assoc(_) => {
+                    self.dcx().emit_err(errors::AbiCustomSafeFunction {
+                        span: sig.span,
+                        unsafe_span: sig.span.shrink_to_lo(),
+                    });
+                }
+            },
+        }
+
+        // An `extern "custom"` function cannot be `async` and/or `gen`.
+        if let Some(coroutine_kind) = sig.header.coroutine_kind {
+            let coroutine_kind_span = self
+                .sess
+                .psess
+                .source_map()
+                .span_until_non_whitespace(coroutine_kind.span().to(sig.span));
+
+            self.dcx().emit_err(errors::AbiCustomCoroutine {
+                span: sig.span,
+                coroutine_kind_span,
+                coroutine_kind_str: coroutine_kind.as_str(),
+            });
+        }
+
+        // An `extern "custom"` function must not have any parameters or return type.
+        let mut spans: Vec<_> = sig.decl.inputs.iter().map(|p| p.span).collect();
+        if let FnRetTy::Ty(ref ret_ty) = sig.decl.output {
+            spans.push(ret_ty.span);
+        }
+
+        if !spans.is_empty() {
+            let header_span = sig.header.span().unwrap_or(sig.span.shrink_to_lo());
+            let suggestion_span = header_span.shrink_to_hi().to(sig.decl.output.span());
+            let padding = if header_span.is_empty() { "" } else { " " };
+
+            self.dcx().emit_err(errors::AbiCustomInvalidSignature {
+                spans,
+                symbol: ident.name,
+                suggestion_span,
+                padding,
+            });
+        }
+    }
+
     /// This ensures that items can only be `unsafe` (or unmarked) outside of extern
     /// blocks.
     ///
@@ -1005,7 +1073,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 if abi.is_none() {
                     self.handle_missing_abi(*extern_span, item.id);
                 }
-                self.with_in_extern_mod(*safety, |this| {
+
+                let extern_abi = abi.and_then(|abi| ExternAbi::from_str(abi.symbol.as_str()).ok());
+                self.with_in_extern_mod(*safety, extern_abi, |this| {
                     visit::walk_item(this, item);
                 });
                 self.extern_mod_span = old_item;
@@ -1145,6 +1215,9 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                 self.check_foreign_fn_bodyless(*ident, body.as_deref());
                 self.check_foreign_fn_headerless(sig.header);
                 self.check_foreign_item_ascii_only(*ident);
+                if self.extern_mod_abi == Some(ExternAbi::Custom) {
+                    self.check_custom_abi(FnCtxt::Foreign, ident, sig);
+                }
             }
             ForeignItemKind::TyAlias(box TyAlias {
                 defaultness,
@@ -1352,6 +1425,13 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
             self.check_item_safety(span, safety);
         }
 
+        if let FnKind::Fn(ctxt, _, fun) = fk
+            && let Extern::Explicit(str_lit, _) = fun.sig.header.ext
+            && let Ok(ExternAbi::Custom) = ExternAbi::from_str(str_lit.symbol.as_str())
+        {
+            self.check_custom_abi(ctxt, &fun.ident, &fun.sig);
+        }
+
         self.check_c_variadic_type(fk);
 
         // Functions cannot both be `const async` or `const gen`
@@ -1703,6 +1783,7 @@ pub fn check_crate(
         outer_impl_trait_span: None,
         disallow_tilde_const: Some(TildeConstReason::Item),
         extern_mod_safety: None,
+        extern_mod_abi: None,
         lint_node_id: CRATE_NODE_ID,
         is_sdylib_interface,
         lint_buffer: lints,