Auto merge of #93457 - matthiaskrgr:rollup-e43ry1l, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #88205 (Add Explanation For Error E0772)
 - #92274 (Add `intrinsics::const_deallocate`)
 - #93236 (Make `NonNull::new` `const`)
 - #93299 (Fix dot separator when there is no source link)
 - #93410 (kmc-solid: Implement `net::FileDesc::duplicate`)
 - #93424 (fix nit)
 - #93431 (remove unused `jemallocator` crate)
 - #93453 (Add GUI theme change test)

Failed merges:

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

Author: bors

Cargo.lock

@@ -3319,7 +3319,6 @@ dependencies = [
  "rustc_codegen_ssa",
  "rustc_driver",
  "tikv-jemalloc-sys",
- "tikv-jemallocator",
 ]
 
 [[package]]
@@ -5164,16 +5163,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "tikv-jemallocator"
-version = "0.4.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3c14a5a604eb8715bc5785018a37d00739b180bcf609916ddf4393d33d49ccdf"
-dependencies = [
- "libc",
- "tikv-jemalloc-sys",
-]
-
 [[package]]
 name = "time"
 version = "0.1.43"

compiler/rustc/Cargo.toml

@@ -15,11 +15,7 @@ version = '0.4.0'
 optional = true
 features = ['unprefixed_malloc_on_supported_platforms']
 
-[dependencies.tikv-jemallocator]
-version = '0.4.0'
-optional = true
-
 [features]
-jemalloc = ['tikv-jemalloc-sys', 'tikv-jemallocator']
+jemalloc = ['tikv-jemalloc-sys']
 llvm = ['rustc_driver/llvm']
 max_level_info = ['rustc_driver/max_level_info']

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -369,6 +369,16 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }
             }
 
+            sym::const_allocate => {
+                // returns a null pointer at runtime.
+                bx.const_null(bx.type_i8p())
+            }
+
+            sym::const_deallocate => {
+                // nop at runtime.
+                return;
+            }
+
             // This requires that atomic intrinsics follow a specific naming pattern:
             // "atomic_<operation>[_<ordering>]", and no ordering means SeqCst
             name if name_str.starts_with("atomic_") => {

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -347,6 +347,33 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                 )?;
                 ecx.write_pointer(ptr, dest)?;
             }
+            sym::const_deallocate => {
+                let ptr = ecx.read_pointer(&args[0])?;
+                let size = ecx.read_scalar(&args[1])?.to_machine_usize(ecx)?;
+                let align = ecx.read_scalar(&args[2])?.to_machine_usize(ecx)?;
+
+                let size = Size::from_bytes(size);
+                let align = match Align::from_bytes(align) {
+                    Ok(a) => a,
+                    Err(err) => throw_ub_format!("align has to be a power of 2, {}", err),
+                };
+
+                // If an allocation is created in an another const,
+                // we don't deallocate it.
+                let (alloc_id, _, _) = ecx.memory.ptr_get_alloc(ptr)?;
+                let is_allocated_in_another_const = matches!(
+                    ecx.tcx.get_global_alloc(alloc_id),
+                    Some(interpret::GlobalAlloc::Memory(_))
+                );
+
+                if !is_allocated_in_another_const {
+                    ecx.memory.deallocate(
+                        ptr,
+                        Some((size, align)),
+                        interpret::MemoryKind::Machine(MemoryKind::Heap),
+                    )?;
+                }
+            }
             _ => {
                 return Err(ConstEvalErrKind::NeedsRfc(format!(
                     "calling intrinsic `{}`",

compiler/rustc_error_codes/src/error_codes.rs

@@ -472,6 +472,7 @@ E0768: include_str!("./error_codes/E0768.md"),
 E0769: include_str!("./error_codes/E0769.md"),
 E0770: include_str!("./error_codes/E0770.md"),
 E0771: include_str!("./error_codes/E0771.md"),
+E0772: include_str!("./error_codes/E0772.md"),
 E0773: include_str!("./error_codes/E0773.md"),
 E0774: include_str!("./error_codes/E0774.md"),
 E0775: include_str!("./error_codes/E0775.md"),
@@ -642,5 +643,4 @@ E0787: include_str!("./error_codes/E0787.md"),
 //  E0723, // unstable feature in `const` context
     E0726, // non-explicit (not `'_`) elided lifetime in unsupported position
 //  E0738, // Removed; errored on `#[track_caller] fn`s in `extern "Rust" { ... }`.
-    E0772, // `'static' obligation coming from `impl dyn Trait {}` or `impl Foo for dyn Bar {}`.
 }

compiler/rustc_error_codes/src/error_codes/E0772.md

@@ -0,0 +1,89 @@
+A trait object has some specific lifetime `'1`, but it was used in a way that
+requires it to have a `'static` lifetime.
+
+Example of erroneous code:
+
+```compile_fail,E0772
+trait BooleanLike {}
+trait Person {}
+
+impl BooleanLike for bool {}
+
+impl dyn Person {
+    fn is_cool(&self) -> bool {
+        // hey you, you're pretty cool
+        true
+    }
+}
+
+fn get_is_cool<'p>(person: &'p dyn Person) -> impl BooleanLike {
+    // error: `person` has an anonymous lifetime `'p` but calling
+    //        `print_cool_fn` introduces an implicit `'static` lifetime
+    //        requirement
+    person.is_cool()
+}
+```
+
+The trait object `person` in the function `get_is_cool`, while already being
+behind a reference with lifetime `'p`, also has it's own implicit lifetime,
+`'2`.
+
+Lifetime `'2` represents the data the trait object might hold inside, for
+example:
+
+```
+trait MyTrait {}
+
+struct MyStruct<'a>(&'a i32);
+
+impl<'a> MyTrait for MyStruct<'a> {}
+```
+
+With this scenario, if a trait object of `dyn MyTrait + '2` was made from
+`MyStruct<'a>`, `'a` must live as long, if not longer than `'2`. This allows the
+trait object's internal data to be accessed safely from any trait methods. This
+rule also goes for any lifetime any struct made into a trait object may have.
+
+In the implementation for `dyn Person`, the `'2` lifetime representing the
+internal data was ommitted, meaning that the compiler inferred the lifetime
+`'static`. As a result, the implementation's `is_cool` is inferred by the
+compiler to look like this:
+
+```
+# trait Person {}
+#
+# impl dyn Person {
+fn is_cool<'a>(self: &'a (dyn Person + 'static)) -> bool {unimplemented!()}
+# }
+```
+
+While the `get_is_cool` function is inferred to look like this:
+
+```
+# trait Person {}
+# trait BooleanLike {}
+#
+fn get_is_cool<'p, R: BooleanLike>(person: &'p (dyn Person + 'p)) -> R {
+    unimplemented!()
+}
+```
+
+Which brings us to the core of the problem; the assignment of type
+`&'_ (dyn Person + '_)` to type `&'_ (dyn Person + 'static)` is impossible.
+
+Fixing it is as simple as being generic over lifetime `'2`, as to prevent the
+compiler from inferring it as `'static`:
+
+```
+# trait Person {}
+#
+impl<'d> dyn Person + 'd {/* ... */}
+
+// This works too, and is more elegant:
+//impl dyn Person + '_ {/* ... */}
+```
+
+See the [Rust Reference on Trait Object Lifetime Bounds][trait-objects] for
+more information on trait object lifetimes.
+
+[trait-object-lifetime-bounds]: https://doc.rust-lang.org/reference/types/trait-object.html#trait-object-lifetime-bounds

compiler/rustc_middle/src/ty/sty.rs

@@ -1810,7 +1810,7 @@ impl<'tcx> TyS<'tcx> {
     pub fn sequence_element_type(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
         match self.kind() {
             Array(ty, _) | Slice(ty) => ty,
-            Str => tcx.mk_mach_uint(ty::UintTy::U8),
+            Str => tcx.types.u8,
             _ => bug!("`sequence_element_type` called on non-sequence value: {}", self),
         }
     }

compiler/rustc_span/src/symbol.rs

@@ -461,6 +461,7 @@ symbols! {
         const_async_blocks,
         const_compare_raw_pointers,
         const_constructor,
+        const_deallocate,
         const_eval_limit,
         const_eval_select,
         const_eval_select_ct,

compiler/rustc_typeck/src/check/intrinsic.rs

@@ -297,6 +297,11 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
             sym::const_allocate => {
                 (0, vec![tcx.types.usize, tcx.types.usize], tcx.mk_mut_ptr(tcx.types.u8))
             }
+            sym::const_deallocate => (
+                0,
+                vec![tcx.mk_mut_ptr(tcx.types.u8), tcx.types.usize, tcx.types.usize],
+                tcx.mk_unit(),
+            ),
 
             sym::ptr_offset_from => {
                 (1, vec![tcx.mk_imm_ptr(param(0)), tcx.mk_imm_ptr(param(0))], tcx.types.isize)

library/core/src/intrinsics.rs

@@ -1914,10 +1914,31 @@ extern "rust-intrinsic" {
     #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")]
     pub fn ptr_guaranteed_ne<T>(ptr: *const T, other: *const T) -> bool;
 
-    /// Allocate at compile time. Should not be called at runtime.
+    /// Allocates a block of memory at compile time.
+    /// At runtime, just returns a null pointer.
+    ///
+    /// # Safety
+    ///
+    /// - The `align` argument must be a power of two.
+    ///    - At compile time, a compile error occurs if this constraint is violated.
+    ///    - At runtime, it is not checked.
     #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
     pub fn const_allocate(size: usize, align: usize) -> *mut u8;
 
+    /// Deallocates a memory which allocated by `intrinsics::const_allocate` at compile time.
+    /// At runtime, does nothing.
+    ///
+    /// # Safety
+    ///
+    /// - The `align` argument must be a power of two.
+    ///    - At compile time, a compile error occurs if this constraint is violated.
+    ///    - At runtime, it is not checked.
+    /// - If the `ptr` is created in an another const, this intrinsic doesn't deallocate it.
+    /// - If the `ptr` is pointing to a local variable, this intrinsic doesn't deallocate it.
+    #[rustc_const_unstable(feature = "const_heap", issue = "79597")]
+    #[cfg(not(bootstrap))]
+    pub fn const_deallocate(ptr: *mut u8, size: usize, align: usize);
+
     /// Determines whether the raw bytes of the two values are equal.
     ///
     /// This is particularly handy for arrays, since it allows things like just