Rollup merge of #96913 - Urgau:rfc3239-part2, r=petrochenkov

[rust.git] / compiler / rustc_target / src / abi / mod.rs

diff --git a/compiler/rustc_target/src/abi/mod.rs b/compiler/rustc_target/src/abi/mod.rs
index 0e8fd9cc93fd120d97da310d45135688e0e01270..a771369c80789448c90f8c7cc726fd2721528382 100644 (file)
--- a/compiler/rustc_target/src/abi/mod.rs
+++ b/compiler/rustc_target/src/abi/mod.rs
@@ -276,12 +276,19 @@ fn to_json(&self) -> Json {
 }
 
 /// Size of a type in bytes.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Encodable, Decodable)]
 #[derive(HashStable_Generic)]
 pub struct Size {
     raw: u64,
 }
 
+// This is debug-printed a lot in larger structs, don't waste too much space there
+impl fmt::Debug for Size {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Size({} bytes)", self.bytes())
+    }
+}
+
 impl Size {
     pub const ZERO: Size = Size { raw: 0 };
 
@@ -485,12 +492,19 @@ unsafe fn backward_unchecked(start: Self, count: usize) -> Self {
 }
 
 /// Alignment of a type in bytes (always a power of two).
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Encodable, Decodable)]
 #[derive(HashStable_Generic)]
 pub struct Align {
     pow2: u8,
 }
 
+// This is debug-printed a lot in larger structs, don't waste too much space there
+impl fmt::Debug for Align {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "Align({} bytes)", self.bytes())
+    }
+}
+
 impl Align {
     pub const ONE: Align = Align { pow2: 0 };
 
@@ -880,6 +894,15 @@ pub fn is_always_valid<C: HasDataLayout>(&self, cx: &C) -> bool {
             Scalar::Union { .. } => true,
         }
     }
+
+    /// Returns `true` if this type can be left uninit.
+    #[inline]
+    pub fn is_uninit_valid(&self) -> bool {
+        match *self {
+            Scalar::Initialized { .. } => false,
+            Scalar::Union { .. } => true,
+        }
+    }
 }
 
 /// Describes how the fields of a type are located in memory.
@@ -1341,6 +1364,14 @@ pub struct PointeeInfo {
     pub address_space: AddressSpace,
 }
 
+/// Used in `might_permit_raw_init` to indicate the kind of initialisation
+/// that is checked to be valid
+#[derive(Copy, Clone, Debug)]
+pub enum InitKind {
+    Zero,
+    Uninit,
+}
+
 /// Trait that needs to be implemented by the higher-level type representation
 /// (e.g. `rustc_middle::ty::Ty`), to provide `rustc_target::abi` functionality.
 pub trait TyAbiInterface<'a, C>: Sized {
@@ -1447,26 +1478,37 @@ pub fn is_zst(&self) -> bool {
 
     /// Determines if this type permits "raw" initialization by just transmuting some
     /// memory into an instance of `T`.
-    /// `zero` indicates if the memory is zero-initialized, or alternatively
-    /// left entirely uninitialized.
+    ///
+    /// `init_kind` indicates if the memory is zero-initialized or left uninitialized.
+    ///
+    /// `strict` is an opt-in debugging flag added in #97323 that enables more checks.
+    ///
     /// This is conservative: in doubt, it will answer `true`.
     ///
     /// FIXME: Once we removed all the conservatism, we could alternatively
     /// create an all-0/all-undef constant and run the const value validator to see if
     /// this is a valid value for the given type.
-    pub fn might_permit_raw_init<C>(self, cx: &C, zero: bool) -> bool
+    pub fn might_permit_raw_init<C>(self, cx: &C, init_kind: InitKind, strict: bool) -> bool
     where
         Self: Copy,
         Ty: TyAbiInterface<'a, C>,
         C: HasDataLayout,
     {
         let scalar_allows_raw_init = move |s: Scalar| -> bool {
-            if zero {
-                // The range must contain 0.
-                s.valid_range(cx).contains(0)
-            } else {
-                // The range must include all values.
-                s.is_always_valid(cx)
+            match init_kind {
+                InitKind::Zero => {
+                    // The range must contain 0.
+                    s.valid_range(cx).contains(0)
+                }
+                InitKind::Uninit => {
+                    if strict {
+                        // The type must be allowed to be uninit (which means "is a union").
+                        s.is_uninit_valid()
+                    } else {
+                        // The range must include all values.
+                        s.is_always_valid(cx)
+                    }
+                }
             }
         };
 
@@ -1486,12 +1528,19 @@ pub fn might_permit_raw_init<C>(self, cx: &C, zero: bool) -> bool
         // If we have not found an error yet, we need to recursively descend into fields.
         match &self.fields {
             FieldsShape::Primitive | FieldsShape::Union { .. } => {}
-            FieldsShape::Array { .. } => {
-                // FIXME(#66151): For now, we are conservative and do not check arrays.
+            FieldsShape::Array { count, .. } => {
+                // FIXME(#66151): For now, we are conservative and do not check arrays by default.
+                if strict
+                    && *count > 0
+                    && !self.field(cx, 0).might_permit_raw_init(cx, init_kind, strict)
+                {
+                    // Found non empty array with a type that is unhappy about this kind of initialization
+                    return false;
+                }
             }
             FieldsShape::Arbitrary { offsets, .. } => {
                 for idx in 0..offsets.len() {
-                    if !self.field(cx, idx).might_permit_raw_init(cx, zero) {
+                    if !self.field(cx, idx).might_permit_raw_init(cx, init_kind, strict) {
                         // We found a field that is unhappy with this kind of initialization.
                         return false;
                     }