Rollup merge of rust-lang#138028 - workingjubilee:is-rustic-abi, r=compiler-errors

compiler: add `ExternAbi::is_rustic_abi`

Various parts of the compiler were hand-rolling this extremely simple check that is nonetheless easy to get wrong as the compiler evolves over time. Discourage them from being so "original" again by replacing it with a single implementation on the type that represents these ABIs. This simplifies a surprising amount of code as a result.

Also fixes rust-lang#132981, an ICE that emerged due to other checks being made stricter.

Author: workingjubilee

compiler/rustc_abi/src/extern_abi.rs

@@ -191,6 +191,17 @@ impl StableOrd for ExternAbi {
 }
 
 impl ExternAbi {
+    /// An ABI "like Rust"
+    ///
+    /// These ABIs are fully controlled by the Rust compiler, which means they
+    /// - support unwinding with `-Cpanic=unwind`, unlike `extern "C"`
+    /// - often diverge from the C ABI
+    /// - are subject to change between compiler versions
+    pub fn is_rustic_abi(self) -> bool {
+        use ExternAbi::*;
+        matches!(self, Rust | RustCall | RustIntrinsic | RustCold)
+    }
+
     pub fn supports_varargs(self) -> bool {
         // * C and Cdecl obviously support varargs.
         // * C can be based on Aapcs, SysV64 or Win64, so they must support varargs.

compiler/rustc_lint/src/types.rs

@@ -1,7 +1,7 @@
 use std::iter;
 use std::ops::ControlFlow;
 
-use rustc_abi::{BackendRepr, ExternAbi, TagEncoding, VariantIdx, Variants, WrappingRange};
+use rustc_abi::{BackendRepr, TagEncoding, VariantIdx, Variants, WrappingRange};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::DiagMessage;
 use rustc_hir::intravisit::VisitorExt;
@@ -1349,7 +1349,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
             ty::FnPtr(sig_tys, hdr) => {
                 let sig = sig_tys.with(hdr);
-                if self.is_internal_abi(sig.abi()) {
+                if sig.abi().is_rustic_abi() {
                     return FfiUnsafe {
                         ty,
                         reason: fluent::lint_improper_ctypes_fnptr_reason,
@@ -1552,13 +1552,6 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         self.check_type_for_ffi_and_report_errors(span, ty, true, false);
     }
 
-    fn is_internal_abi(&self, abi: ExternAbi) -> bool {
-        matches!(
-            abi,
-            ExternAbi::Rust | ExternAbi::RustCall | ExternAbi::RustCold | ExternAbi::RustIntrinsic
-        )
-    }
-
     /// Find any fn-ptr types with external ABIs in `ty`.
     ///
     /// For example, `Option<extern "C" fn()>` returns `extern "C" fn()`
@@ -1567,17 +1560,16 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         hir_ty: &hir::Ty<'tcx>,
         ty: Ty<'tcx>,
     ) -> Vec<(Ty<'tcx>, Span)> {
-        struct FnPtrFinder<'a, 'b, 'tcx> {
-            visitor: &'a ImproperCTypesVisitor<'b, 'tcx>,
+        struct FnPtrFinder<'tcx> {
             spans: Vec<Span>,
             tys: Vec<Ty<'tcx>>,
         }
 
-        impl<'a, 'b, 'tcx> hir::intravisit::Visitor<'_> for FnPtrFinder<'a, 'b, 'tcx> {
+        impl<'tcx> hir::intravisit::Visitor<'_> for FnPtrFinder<'tcx> {
             fn visit_ty(&mut self, ty: &'_ hir::Ty<'_, AmbigArg>) {
                 debug!(?ty);
                 if let hir::TyKind::BareFn(hir::BareFnTy { abi, .. }) = ty.kind
-                    && !self.visitor.is_internal_abi(*abi)
+                    && !abi.is_rustic_abi()
                 {
                     self.spans.push(ty.span);
                 }
@@ -1586,12 +1578,12 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             }
         }
 
-        impl<'a, 'b, 'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for FnPtrFinder<'a, 'b, 'tcx> {
+        impl<'tcx> ty::visit::TypeVisitor<TyCtxt<'tcx>> for FnPtrFinder<'tcx> {
             type Result = ();
 
             fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
                 if let ty::FnPtr(_, hdr) = ty.kind()
-                    && !self.visitor.is_internal_abi(hdr.abi)
+                    && !hdr.abi.is_rustic_abi()
                 {
                     self.tys.push(ty);
                 }
@@ -1600,7 +1592,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             }
         }
 
-        let mut visitor = FnPtrFinder { visitor: self, spans: Vec::new(), tys: Vec::new() };
+        let mut visitor = FnPtrFinder { spans: Vec::new(), tys: Vec::new() };
         ty.visit_with(&mut visitor);
         visitor.visit_ty_unambig(hir_ty);
 
@@ -1615,13 +1607,13 @@ impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
 
         match it.kind {
             hir::ForeignItemKind::Fn(sig, _, _) => {
-                if vis.is_internal_abi(abi) {
+                if abi.is_rustic_abi() {
                     vis.check_fn(it.owner_id.def_id, sig.decl)
                 } else {
                     vis.check_foreign_fn(it.owner_id.def_id, sig.decl);
                 }
             }
-            hir::ForeignItemKind::Static(ty, _, _) if !vis.is_internal_abi(abi) => {
+            hir::ForeignItemKind::Static(ty, _, _) if !abi.is_rustic_abi() => {
                 vis.check_foreign_static(it.owner_id, ty.span);
             }
             hir::ForeignItemKind::Static(..) | hir::ForeignItemKind::Type => (),
@@ -1775,7 +1767,7 @@ impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
         };
 
         let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
-        if vis.is_internal_abi(abi) {
+        if abi.is_rustic_abi() {
             vis.check_fn(id, decl);
         } else {
             vis.check_foreign_fn(id, decl);

compiler/rustc_mir_transform/src/ffi_unwind_calls.rs

@@ -53,11 +53,7 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
 
         // Rust calls cannot themselves create foreign unwinds.
         // We assume this is true for intrinsics as well.
-        if let ExternAbi::RustIntrinsic
-        | ExternAbi::Rust
-        | ExternAbi::RustCall
-        | ExternAbi::RustCold = sig.abi()
-        {
+        if sig.abi().is_rustic_abi() {
             continue;
         };
 

compiler/rustc_monomorphize/src/mono_checks/abi_check.rs

@@ -1,6 +1,6 @@
 //! This module ensures that if a function's ABI requires a particular target feature,
 //! that target feature is enabled both on the callee and all callers.
-use rustc_abi::{BackendRepr, ExternAbi, RegKind};
+use rustc_abi::{BackendRepr, RegKind};
 use rustc_hir::CRATE_HIR_ID;
 use rustc_middle::mir::{self, traversal};
 use rustc_middle::ty::{self, Instance, InstanceKind, Ty, TyCtxt};
@@ -115,8 +115,8 @@ fn check_call_site_abi<'tcx>(
     span: Span,
     caller: InstanceKind<'tcx>,
 ) {
-    if callee.fn_sig(tcx).abi() == ExternAbi::Rust {
-        // "Rust" ABI never passes arguments in vector registers.
+    if callee.fn_sig(tcx).abi().is_rustic_abi() {
+        // we directly handle the soundness of Rust ABIs
         return;
     }
     let typing_env = ty::TypingEnv::fully_monomorphized();

compiler/rustc_ty_utils/src/abi.rs

@@ -436,10 +436,7 @@ fn fn_abi_sanity_check<'tcx>(
     ) {
         let tcx = cx.tcx();
 
-        if spec_abi == ExternAbi::Rust
-            || spec_abi == ExternAbi::RustCall
-            || spec_abi == ExternAbi::RustCold
-        {
+        if spec_abi.is_rustic_abi() {
             if arg.layout.is_zst() {
                 // Casting closures to function pointers depends on ZST closure types being
                 // omitted entirely in the calling convention.
@@ -687,7 +684,7 @@ fn fn_abi_adjust_for_abi<'tcx>(
 
     let tcx = cx.tcx();
 
-    if abi == ExternAbi::Rust || abi == ExternAbi::RustCall || abi == ExternAbi::RustIntrinsic {
+    if abi.is_rustic_abi() {
         fn_abi.adjust_for_rust_abi(cx, abi);
 
         // Look up the deduced parameter attributes for this function, if we have its def ID and

tests/crashes/132981.rs

@@ -0,0 +1,6 @@
+//@build-pass
+//@compile-flags: -Clink-dead-code=true --crate-type lib
+// We used to not handle all "rustic" ABIs in a (relatively) uniform way,
+// so we failed to fix up arguments for actually passing through the ABI...
+#![feature(rust_cold_cc)]
+pub extern "rust-cold" fn foo(_: [usize; 3]) {}