Auto merge of #146052 - matthiaskrgr:rollup-cfxx9m6, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - #144443 (Make target pointer width in target json an integer)
 - #145174 (Ensure consistent drop for panicking drop in hint::select_unpredictable)
 - #145592 (Fix format string grammar in docs and improve alignment error message for #144023)
 - #145931 (Clarify that align_offset overaligns)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_abi/src/lib.rs

@@ -315,7 +315,7 @@ pub enum TargetDataLayoutErrors<'a> {
     MissingAlignment { cause: &'a str },
     InvalidAlignment { cause: &'a str, err: AlignFromBytesError },
     InconsistentTargetArchitecture { dl: &'a str, target: &'a str },
-    InconsistentTargetPointerWidth { pointer_size: u64, target: u32 },
+    InconsistentTargetPointerWidth { pointer_size: u64, target: u16 },
     InvalidBitsSize { err: String },
     UnknownPointerSpecification { err: String },
 }

compiler/rustc_ast_ir/src/lib.rs

@@ -69,7 +69,7 @@ impl IntTy {
         })
     }
 
-    pub fn normalize(&self, target_width: u32) -> Self {
+    pub fn normalize(&self, target_width: u16) -> Self {
         match self {
             IntTy::Isize => match target_width {
                 16 => IntTy::I16,
@@ -148,7 +148,7 @@ impl UintTy {
         })
     }
 
-    pub fn normalize(&self, target_width: u32) -> Self {
+    pub fn normalize(&self, target_width: u16) -> Self {
         match self {
             UintTy::Usize => match target_width {
                 16 => UintTy::U16,

compiler/rustc_codegen_gcc/target_specs/m68k-unknown-linux-gnu.json

@@ -22,5 +22,5 @@
     "unix"
   ],
   "target-mcount": "_mcount",
-  "target-pointer-width": "32"
+  "target-pointer-width": 32
 }

compiler/rustc_parse_format/src/lib.rs

@@ -858,7 +858,9 @@ impl<'input> Parser<'input> {
             self.errors.insert(
                 0,
                 ParseError {
-                    description: "expected format parameter to occur after `:`".to_owned(),
+                    description:
+                        "expected alignment specifier after `:` in format string; example: `{:>?}`"
+                            .to_owned(),
                     note: None,
                     label: format!("expected `{}` to occur after `:`", alignment),
                     span: range,

compiler/rustc_target/src/spec/json.rs

@@ -25,10 +25,7 @@ impl Target {
         let mut base = Target {
             llvm_target: json.llvm_target,
             metadata: Default::default(),
-            pointer_width: json
-                .target_pointer_width
-                .parse()
-                .map_err(|err| format!("invalid target-pointer-width: {err}"))?,
+            pointer_width: json.target_pointer_width,
             data_layout: json.data_layout,
             arch: json.arch,
             options: Default::default(),
@@ -245,19 +242,17 @@ impl ToJson for Target {
         target.update_to_cli();
 
         macro_rules! target_val {
-            ($attr:ident) => {{
-                let name = (stringify!($attr)).replace("_", "-");
-                d.insert(name, target.$attr.to_json());
+            ($attr:ident) => {
+                target_val!($attr, (stringify!($attr)).replace("_", "-"))
+            };
+            ($attr:ident, $json_name:expr) => {{
+                let name = $json_name;
+                d.insert(name.into(), target.$attr.to_json());
             }};
         }
 
         macro_rules! target_option_val {
-            ($attr:ident) => {{
-                let name = (stringify!($attr)).replace("_", "-");
-                if default.$attr != target.$attr {
-                    d.insert(name, target.$attr.to_json());
-                }
-            }};
+            ($attr:ident) => {{ target_option_val!($attr, (stringify!($attr)).replace("_", "-")) }};
             ($attr:ident, $json_name:expr) => {{
                 let name = $json_name;
                 if default.$attr != target.$attr {
@@ -290,7 +285,7 @@ impl ToJson for Target {
 
         target_val!(llvm_target);
         target_val!(metadata);
-        d.insert("target-pointer-width".to_string(), self.pointer_width.to_string().to_json());
+        target_val!(pointer_width, "target-pointer-width");
         target_val!(arch);
         target_val!(data_layout);
 
@@ -463,7 +458,7 @@ struct TargetSpecJsonMetadata {
 #[serde(deny_unknown_fields)]
 struct TargetSpecJson {
     llvm_target: StaticCow<str>,
-    target_pointer_width: String,
+    target_pointer_width: u16,
     data_layout: StaticCow<str>,
     arch: StaticCow<str>,
 

compiler/rustc_target/src/spec/mod.rs

@@ -2331,7 +2331,7 @@ pub struct Target {
     /// Used for generating target documentation.
     pub metadata: TargetMetadata,
     /// Number of bits in a pointer. Influences the `target_pointer_width` `cfg` variable.
-    pub pointer_width: u32,
+    pub pointer_width: u16,
     /// Architecture to use for ABI considerations. Valid options include: "x86",
     /// "x86_64", "arm", "aarch64", "mips", "powerpc", "powerpc64", and others.
     pub arch: StaticCow<str>,

compiler/rustc_target/src/tests.rs

@@ -7,7 +7,7 @@ fn report_unused_fields() {
         "arch": "powerpc64",
         "data-layout": "e-m:e-i64:64-n32:64",
         "llvm-target": "powerpc64le-elf",
-        "target-pointer-width": "64",
+        "target-pointer-width": 64,
         "code-mode": "foo"
     }
     "#;

library/alloc/src/fmt.rs

@@ -354,7 +354,7 @@
 //! sign := '+' | '-'
 //! width := count
 //! precision := count | '*'
-//! type := '?' | 'x?' | 'X?' | identifier
+//! type := '?' | 'x?' | 'X?' | 'o' | 'x' | 'X' | 'p' | 'b' | 'e' | 'E'
 //! count := parameter | integer
 //! parameter := argument '$'
 //! ```

library/compiler-builtins/etc/thumbv7em-none-eabi-renamed.json

@@ -19,5 +19,5 @@
   },
   "panic-strategy": "abort",
   "relocation-model": "static",
-  "target-pointer-width": "32"
+  "target-pointer-width": 32
 }

library/core/src/hint.rs

@@ -776,12 +776,45 @@ pub fn select_unpredictable<T>(condition: bool, true_val: T, false_val: T) -> T
     // Change this to use ManuallyDrop instead.
     let mut true_val = MaybeUninit::new(true_val);
     let mut false_val = MaybeUninit::new(false_val);
+
+    struct DropOnPanic<T> {
+        // Invariant: valid pointer and points to an initialized value that is not further used,
+        // i.e. it can be dropped by this guard.
+        inner: *mut T,
+    }
+
+    impl<T> Drop for DropOnPanic<T> {
+        fn drop(&mut self) {
+            // SAFETY: Must be guaranteed on construction of local type `DropOnPanic`.
+            unsafe { self.inner.drop_in_place() }
+        }
+    }
+
+    let true_ptr = true_val.as_mut_ptr();
+    let false_ptr = false_val.as_mut_ptr();
+
     // SAFETY: The value that is not selected is dropped, and the selected one
     // is returned. This is necessary because the intrinsic doesn't drop the
     // value that is  not selected.
     unsafe {
-        crate::intrinsics::select_unpredictable(!condition, &mut true_val, &mut false_val)
-            .assume_init_drop();
+        // Extract the selected value first, ensure it is dropped as well if dropping the unselected
+        // value panics. We construct a temporary by-pointer guard around the selected value while
+        // dropping the unselected value. Arguments overlap here, so we can not use mutable
+        // reference for these arguments.
+        let guard = crate::intrinsics::select_unpredictable(condition, true_ptr, false_ptr);
+        let drop = crate::intrinsics::select_unpredictable(condition, false_ptr, true_ptr);
+
+        // SAFETY: both pointers are well-aligned and point to initialized values inside a
+        // `MaybeUninit` each. In both possible values for `condition` the pointer `guard` and
+        // `drop` do not alias (even though the two argument pairs we have selected from did alias
+        // each other).
+        let guard = DropOnPanic { inner: guard };
+        drop.drop_in_place();
+        crate::mem::forget(guard);
+
+        // Note that it is important to use the values here. Reading from the pointer we got makes
+        // LLVM forget the !unpredictable annotation sometimes (in tests, integer sized values in
+        // particular seemed to confuse it, also observed in llvm/llvm-project #82340).
         crate::intrinsics::select_unpredictable(condition, true_val, false_val).assume_init()
     }
 }