Rollup merge of #156884 - folkertdev:revert-global-asm-inner-item, r=workingjubilee

Revert "Allow `global_asm!` in statement positions"

This reverts commit 450cdb5.

Based on discussion in [#t-lang > insta-stable `global_asm!` as inner items](https://rust-lang.zulipchat.com/#narrow/channel/213817-t-lang/topic/insta-stable.20.60global_asm.21.60.20as.20inner.20items/with/597411711), #156582 should not have been merged without FCP.

We've also since found a bug in the implementation (or really, an assumption in the existing code that the PR invalidates), so to re-land this

- new behavior should be behind a feature gate
- the fix in #156855 (comment) should be included (and reviewed by someone familiar with `rustc_resolve`)

Then we keep it unstable for a bit, and see if the fuzzer finds anything else. Nothing here is particularly controversial I think, but we need to do our due diligence.

r? @ghost

Author: JonathanBrouwer

compiler/rustc_builtin_macros/src/asm.rs

@@ -10,7 +10,7 @@ use rustc_parse_format as parse;
 use rustc_session::lint;
 use rustc_span::{ErrorGuaranteed, InnerSpan, Span, Symbol, sym};
 use rustc_target::asm::InlineAsmArch;
-use smallvec::{SmallVec, smallvec};
+use smallvec::smallvec;
 
 use crate::errors;
 use crate::util::{ExprToSpannedString, expr_to_spanned_string};
@@ -26,24 +26,6 @@ struct ValidatedAsmArgs {
     pub options_spans: Vec<Span>,
 }
 
-struct MacGlobalAsm {
-    item: ast::Item,
-}
-
-impl MacResult for MacGlobalAsm {
-    fn make_items(self: Box<Self>) -> Option<SmallVec<[Box<ast::Item>; 1]>> {
-        Some(smallvec![Box::new(self.item)])
-    }
-
-    fn make_stmts(self: Box<Self>) -> Option<SmallVec<[ast::Stmt; 1]>> {
-        Some(smallvec![ast::Stmt {
-            id: ast::DUMMY_NODE_ID,
-            span: self.item.span,
-            kind: ast::StmtKind::Item(Box::new(self.item)),
-        }])
-    }
-}
-
 fn parse_args<'a>(
     ecx: &ExtCtxt<'a>,
     sp: Span,
@@ -668,20 +650,18 @@ pub(super) fn expand_global_asm<'cx>(
                 return ExpandResult::Retry(());
             };
             match mac {
-                Ok(inline_asm) => Box::new(MacGlobalAsm {
-                    item: ast::Item {
-                        attrs: ast::AttrVec::new(),
-                        id: ast::DUMMY_NODE_ID,
-                        kind: ast::ItemKind::GlobalAsm(Box::new(inline_asm)),
-                        vis: ast::Visibility {
-                            span: sp.shrink_to_lo(),
-                            kind: ast::VisibilityKind::Inherited,
-                            tokens: None,
-                        },
-                        span: sp,
+                Ok(inline_asm) => MacEager::items(smallvec![Box::new(ast::Item {
+                    attrs: ast::AttrVec::new(),
+                    id: ast::DUMMY_NODE_ID,
+                    kind: ast::ItemKind::GlobalAsm(Box::new(inline_asm)),
+                    vis: ast::Visibility {
+                        span: sp.shrink_to_lo(),
+                        kind: ast::VisibilityKind::Inherited,
                         tokens: None,
                     },
-                }),
+                    span: sp,
+                    tokens: None,
+                })]),
                 Err(guar) => DummyResult::any(sp, guar),
             }
         }

tests/ui/asm/naked-functions.rs

@@ -6,20 +6,14 @@
 #![feature(asm_unwind, linkage, rustc_attrs, cfg_target_object_format)]
 #![crate_type = "lib"]
 
-use std::arch::{asm, global_asm, naked_asm};
+use std::arch::{asm, naked_asm};
 
 #[unsafe(naked)]
 pub extern "C" fn inline_asm_macro() {
     unsafe { asm!("", options(raw)) };
     //~^ERROR the `asm!` macro is not allowed in naked functions
 }
 
-#[unsafe(naked)]
-pub extern "C" fn global_asm_macro() {
-    //~^ERROR naked functions must contain a single `naked_asm!` invocation
-    global_asm!("");
-}
-
 #[repr(C)]
 pub struct P {
     x: u8,

tests/ui/asm/naked-functions.stderr

@@ -1,71 +1,71 @@
 error: the `in` operand cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:53:29
+  --> $DIR/naked-functions.rs:47:29
    |
 LL |     naked_asm!("/* {0} */", in(reg) a)
    |                             ^^ the `in` operand is not meaningful for global-scoped inline assembly, remove it
 
 error: the `in` operand cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:74:10
+  --> $DIR/naked-functions.rs:68:10
    |
 LL |          in(reg) a,
    |          ^^ the `in` operand is not meaningful for global-scoped inline assembly, remove it
 
 error: the `noreturn` option cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:94:28
+  --> $DIR/naked-functions.rs:88:28
    |
 LL |     naked_asm!("", options(noreturn));
    |                            ^^^^^^^^ the `noreturn` option is not meaningful for global-scoped inline assembly
 
 error: the `nomem` option cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:111:28
+  --> $DIR/naked-functions.rs:105:28
    |
 LL |     naked_asm!("", options(nomem, preserves_flags));
    |                            ^^^^^ the `nomem` option is not meaningful for global-scoped inline assembly
 
 error: the `preserves_flags` option cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:111:35
+  --> $DIR/naked-functions.rs:105:35
    |
 LL |     naked_asm!("", options(nomem, preserves_flags));
    |                                   ^^^^^^^^^^^^^^^ the `preserves_flags` option is not meaningful for global-scoped inline assembly
 
 error: the `readonly` option cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:118:28
+  --> $DIR/naked-functions.rs:112:28
    |
 LL |     naked_asm!("", options(readonly, nostack), options(pure));
    |                            ^^^^^^^^ the `readonly` option is not meaningful for global-scoped inline assembly
 
 error: the `nostack` option cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:118:38
+  --> $DIR/naked-functions.rs:112:38
    |
 LL |     naked_asm!("", options(readonly, nostack), options(pure));
    |                                      ^^^^^^^ the `nostack` option is not meaningful for global-scoped inline assembly
 
 error: the `pure` option cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:118:56
+  --> $DIR/naked-functions.rs:112:56
    |
 LL |     naked_asm!("", options(readonly, nostack), options(pure));
    |                                                        ^^^^ the `pure` option is not meaningful for global-scoped inline assembly
 
 error: the `may_unwind` option cannot be used with `naked_asm!`
-  --> $DIR/naked-functions.rs:126:28
+  --> $DIR/naked-functions.rs:120:28
    |
 LL |     naked_asm!("", options(may_unwind));
    |                            ^^^^^^^^^^ the `may_unwind` option is not meaningful for global-scoped inline assembly
 
 error: this is a user specified error
-  --> $DIR/naked-functions.rs:157:5
+  --> $DIR/naked-functions.rs:151:5
    |
 LL |     compile_error!("this is a user specified error")
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this is a user specified error
-  --> $DIR/naked-functions.rs:163:5
+  --> $DIR/naked-functions.rs:157:5
    |
 LL |     compile_error!("this is a user specified error");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: asm template must be a string literal
-  --> $DIR/naked-functions.rs:170:16
+  --> $DIR/naked-functions.rs:164:16
    |
 LL |     naked_asm!(invalid_syntax)
    |                ^^^^^^^^^^^^^^
@@ -76,46 +76,40 @@ error[E0787]: the `asm!` macro is not allowed in naked functions
 LL |     unsafe { asm!("", options(raw)) };
    |              ^^^^^^^^^^^^^^^^^^^^^^ consider using the `naked_asm!` macro instead
 
-error[E0787]: naked functions must contain a single `naked_asm!` invocation
-  --> $DIR/naked-functions.rs:18:1
-   |
-LL | pub extern "C" fn global_asm_macro() {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: patterns not allowed in naked function parameters
-  --> $DIR/naked-functions.rs:31:5
+  --> $DIR/naked-functions.rs:25:5
    |
 LL |     mut a: u32,
    |     ^^^^^
 
 error: patterns not allowed in naked function parameters
-  --> $DIR/naked-functions.rs:33:5
+  --> $DIR/naked-functions.rs:27:5
    |
 LL |     &b: &i32,
    |     ^^
 
 error: patterns not allowed in naked function parameters
-  --> $DIR/naked-functions.rs:35:6
+  --> $DIR/naked-functions.rs:29:6
    |
 LL |     (None | Some(_)): Option<std::ptr::NonNull<u8>>,
    |      ^^^^^^^^^^^^^^
 
 error: patterns not allowed in naked function parameters
-  --> $DIR/naked-functions.rs:37:5
+  --> $DIR/naked-functions.rs:31:5
    |
 LL |     P { x, y }: P,
    |     ^^^^^^^^^^
 
 error: referencing function parameters is not allowed in naked functions
-  --> $DIR/naked-functions.rs:46:5
+  --> $DIR/naked-functions.rs:40:5
    |
 LL |     a + 1
    |     ^
    |
    = help: follow the calling convention in asm block to use parameters
 
 error[E0787]: naked functions must contain a single `naked_asm!` invocation
-  --> $DIR/naked-functions.rs:44:1
+  --> $DIR/naked-functions.rs:38:1
    |
 LL | pub extern "C" fn inc(a: u32) -> u32 {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -124,7 +118,7 @@ LL |     a + 1
    |     ----- not allowed in naked functions
 
 error[E0787]: naked functions must contain a single `naked_asm!` invocation
-  --> $DIR/naked-functions.rs:58:1
+  --> $DIR/naked-functions.rs:52:1
    |
 LL | pub extern "C" fn inc_closure(a: u32) -> u32 {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -133,7 +127,7 @@ LL |     (|| a + 1)()
    |     ------------ not allowed in naked functions
 
 error[E0787]: naked functions must contain a single `naked_asm!` invocation
-  --> $DIR/naked-functions.rs:64:1
+  --> $DIR/naked-functions.rs:58:1
    |
 LL | pub extern "C" fn unsupported_operands() {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -150,13 +144,13 @@ LL |     let mut e = 0usize;
    |     ------------------- not allowed in naked functions
 
 error[E0787]: naked functions must contain a single `naked_asm!` invocation
-  --> $DIR/naked-functions.rs:86:1
+  --> $DIR/naked-functions.rs:80:1
    |
 LL | pub extern "C" fn missing_assembly() {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error[E0787]: naked functions must contain a single `naked_asm!` invocation
-  --> $DIR/naked-functions.rs:91:1
+  --> $DIR/naked-functions.rs:85:1
    |
 LL | pub extern "C" fn too_many_asm_blocks() {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -165,22 +159,22 @@ LL |     naked_asm!("");
    |     -------------- multiple `naked_asm!` invocations are not allowed in naked functions
 
 error: referencing function parameters is not allowed in naked functions
-  --> $DIR/naked-functions.rs:103:11
+  --> $DIR/naked-functions.rs:97:11
    |
 LL |         *&y
    |           ^
    |
    = help: follow the calling convention in asm block to use parameters
 
 error[E0787]: naked functions must contain a single `naked_asm!` invocation
-  --> $DIR/naked-functions.rs:101:5
+  --> $DIR/naked-functions.rs:95:5
    |
 LL |     pub extern "C" fn inner(y: usize) -> usize {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |
 LL |         *&y
    |         --- not allowed in naked functions
 
-error: aborting due to 26 previous errors
+error: aborting due to 25 previous errors
 
 For more information about this error, try `rustc --explain E0787`.