switch to an allowlist approach

- merge error codes
- use attribute name that is incompatible in error message
- add test for conditional incompatible attribute
- add `linkage` to the allowlist

Author: folkertdev

compiler/rustc_builtin_macros/src/errors.rs

@@ -914,7 +914,7 @@ pub(crate) struct ExpectedItem<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_naked_functions_testing_attribute, code = E0798)]
+#[diag(builtin_macros_naked_functions_testing_attribute, code = E0736)]
 pub struct NakedFunctionTestingAttribute {
     #[primary_span]
     #[label(builtin_macros_naked_attribute)]

compiler/rustc_error_codes/src/error_codes/E0736.md

@@ -1,11 +1,12 @@
 Functions marked with the `#[naked]` attribute are restricted in what other
-code generation attributes they may be marked with.
+attributes they may be marked with.
 
-The following code generation attributes are incompatible with `#[naked]`:
+Notable attributes that are incompatible with `#[naked]` are:
 
-  * `#[inline]`
-  * `#[track_caller]`
-  * `#[target_feature]`
+* `#[inline]`
+* `#[track_caller]`
+* `#[target_feature]`
+* `#[test]`, `#[ignore]`, `#[should_panic]`
 
 Erroneous code example:
 
@@ -18,7 +19,3 @@ fn foo() {}
 These incompatibilities are due to the fact that naked functions deliberately
 impose strict restrictions regarding the code that the compiler is
 allowed to produce for this function.
-
-See [the reference page for codegen attributes] for more information.
-
-[the reference page for codegen attributes]: https://doc.rust-lang.org/reference/attributes/codegen.html

compiler/rustc_error_codes/src/error_codes/E0798.md

@@ -536,7 +536,6 @@ E0794: 0794,
 E0795: 0795,
 E0796: 0796,
 E0797: 0797,
-E0798: 0798,
         );
     )
 }

compiler/rustc_error_codes/src/lib.rs

@@ -482,9 +482,9 @@ passes_naked_functions_asm_block =
 passes_naked_functions_asm_options =
     asm options unsupported in naked functions: {$unsupported_options}
 
-passes_naked_functions_codegen_attribute =
-    cannot use additional code generation attributes with `#[naked]`
-    .label = this attribute is incompatible with `#[naked]`
+passes_naked_functions_incompatible_attribute =
+    attribute incompatible with `#[naked]`
+    .label = the `{$attr}` attribute is incompatible with `#[naked]`
     .naked_attribute = function marked with `#[naked]` here
 
 passes_naked_functions_must_use_noreturn =

compiler/rustc_passes/messages.ftl

@@ -418,17 +418,53 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         target: Target,
         attrs: &[Attribute],
     ) -> bool {
-        const FORBIDDEN: [rustc_span::Symbol; 3] =
-            [sym::track_caller, sym::inline, sym::target_feature];
+        // many attributes don't make sense in combination with #[naked].
+        // Notable attributes that are incompatible with `#[naked]` are:
+        //
+        // * `#[inline]`
+        // * `#[track_caller]`
+        // * `#[target_feature]`
+        // * `#[test]`, `#[ignore]`, `#[should_panic]`
+        //
+        // NOTE: when making changes to this list, check that `error_codes/E0736.md` remains accurate
+        const ALLOW_LIST: &[rustc_span::Symbol] = &[
+            // conditional compilation
+            sym::cfg,
+            sym::cfg_attr,
+            // testing (allowed here so better errors can be generated in `rustc_builtin_macros::test`)
+            sym::test,
+            sym::ignore,
+            sym::should_panic,
+            sym::bench,
+            // diagnostics
+            sym::allow,
+            sym::warn,
+            sym::deny,
+            sym::forbid,
+            sym::deprecated,
+            sym::must_use,
+            // abi, linking and FFI
+            sym::export_name,
+            sym::link_section,
+            sym::linkage,
+            sym::no_mangle,
+            sym::naked,
+            sym::instruction_set,
+            // code generation
+            sym::cold,
+            // documentation
+            sym::doc,
+        ];
 
         match target {
             Target::Fn
             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => {
                 for other_attr in attrs {
-                    if FORBIDDEN.into_iter().any(|name| other_attr.has_name(name)) {
-                        self.dcx().emit_err(errors::NakedFunctionCodegenAttribute {
+                    if !ALLOW_LIST.iter().any(|name| other_attr.has_name(*name)) {
+                        self.dcx().emit_err(errors::NakedFunctionIncompatibleAttribute {
                             span: other_attr.span,
                             naked_span: attr.span,
+                            attr: other_attr.name_or_empty(),
                         });
 
                         return false;

compiler/rustc_passes/src/check_attr.rs

@@ -1183,13 +1183,14 @@ pub struct NakedFunctionsMustUseNoreturn {
 }
 
 #[derive(Diagnostic)]
-#[diag(passes_naked_functions_codegen_attribute, code = E0736)]
-pub struct NakedFunctionCodegenAttribute {
+#[diag(passes_naked_functions_incompatible_attribute, code = E0736)]
+pub struct NakedFunctionIncompatibleAttribute {
     #[primary_span]
     #[label]
     pub span: Span,
     #[label(passes_naked_attribute)]
     pub naked_span: Span,
+    pub attr: Symbol,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_passes/src/errors.rs

@@ -29,3 +29,10 @@ pub unsafe extern "C" fn inline_always() {
 pub unsafe extern "C" fn inline_never() {
     asm!("", options(noreturn));
 }
+
+#[naked]
+#[cfg_attr(all(), inline(never))]
+//~^ ERROR [E0736]
+pub unsafe extern "C" fn conditional_inline_never() {
+    asm!("", options(noreturn));
+}

tests/ui/asm/naked-functions-inline.rs

@@ -1,27 +1,35 @@
-error[E0736]: cannot use additional code generation attributes with `#[naked]`
+error[E0736]: attribute incompatible with `#[naked]`
   --> $DIR/naked-functions-inline.rs:13:1
    |
 LL | #[naked]
    | -------- function marked with `#[naked]` here
 LL | #[inline]
-   | ^^^^^^^^^ this attribute is incompatible with `#[naked]`
+   | ^^^^^^^^^ the `inline` attribute is incompatible with `#[naked]`
 
-error[E0736]: cannot use additional code generation attributes with `#[naked]`
+error[E0736]: attribute incompatible with `#[naked]`
   --> $DIR/naked-functions-inline.rs:20:1
    |
 LL | #[naked]
    | -------- function marked with `#[naked]` here
 LL | #[inline(always)]
-   | ^^^^^^^^^^^^^^^^^ this attribute is incompatible with `#[naked]`
+   | ^^^^^^^^^^^^^^^^^ the `inline` attribute is incompatible with `#[naked]`
 
-error[E0736]: cannot use additional code generation attributes with `#[naked]`
+error[E0736]: attribute incompatible with `#[naked]`
   --> $DIR/naked-functions-inline.rs:27:1
    |
 LL | #[naked]
    | -------- function marked with `#[naked]` here
 LL | #[inline(never)]
-   | ^^^^^^^^^^^^^^^^ this attribute is incompatible with `#[naked]`
+   | ^^^^^^^^^^^^^^^^ the `inline` attribute is incompatible with `#[naked]`
 
-error: aborting due to 3 previous errors
+error[E0736]: attribute incompatible with `#[naked]`
+  --> $DIR/naked-functions-inline.rs:34:19
+   |
+LL | #[naked]
+   | -------- function marked with `#[naked]` here
+LL | #[cfg_attr(all(), inline(never))]
+   |                   ^^^^^^^^^^^^^ the `inline` attribute is incompatible with `#[naked]`
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0736`.

tests/ui/asm/naked-functions-inline.stderr

@@ -0,0 +1,30 @@
+//@ compile-flags: --target armv5te-unknown-linux-gnueabi
+//@ needs-llvm-components: arm
+//@ needs-asm-support
+//@ build-pass
+
+#![crate_type = "lib"]
+#![feature(no_core, lang_items, rustc_attrs, naked_functions)]
+#![no_core]
+
+#[rustc_builtin_macro]
+macro_rules! asm {
+    () => {};
+}
+
+#[lang = "sized"]
+trait Sized {}
+
+#[no_mangle]
+#[naked]
+#[instruction_set(arm::t32)]
+unsafe extern "C" fn test_thumb() {
+    asm!("bx lr", options(noreturn));
+}
+
+#[no_mangle]
+#[naked]
+#[instruction_set(arm::t32)]
+unsafe extern "C" fn test_arm() {
+    asm!("bx lr", options(noreturn));
+}