0cdbeaa2a3
This stabilizes dereferencing immutable raw pointers in const contexts. It does not stabilize `*mut T` dereferencing. This is placed behind the `const_raw_mut_ptr_deref` feature gate.
75 lines
3.0 KiB
Rust
75 lines
3.0 KiB
Rust
// compile-flags: --crate-type=lib
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// normalize-stderr-32bit: "8 bytes" -> "$$TWO_WORDS bytes"
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// normalize-stderr-64bit: "16 bytes" -> "$$TWO_WORDS bytes"
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// normalize-stderr-32bit: "size 4" -> "size $$WORD"
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// normalize-stderr-64bit: "size 8" -> "size $$WORD"
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#![feature(
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core_intrinsics,
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const_raw_ptr_comparison,
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const_ptr_offset,
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)]
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const FOO: &usize = &42;
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macro_rules! check {
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(eq, $a:expr, $b:expr) => {
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pub const _: () =
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assert!(std::intrinsics::ptr_guaranteed_eq($a as *const u8, $b as *const u8));
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};
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(ne, $a:expr, $b:expr) => {
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pub const _: () =
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assert!(std::intrinsics::ptr_guaranteed_ne($a as *const u8, $b as *const u8));
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};
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(!eq, $a:expr, $b:expr) => {
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pub const _: () =
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assert!(!std::intrinsics::ptr_guaranteed_eq($a as *const u8, $b as *const u8));
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};
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(!ne, $a:expr, $b:expr) => {
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pub const _: () =
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assert!(!std::intrinsics::ptr_guaranteed_ne($a as *const u8, $b as *const u8));
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};
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}
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check!(eq, 0, 0);
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check!(ne, 0, 1);
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check!(!eq, 0, 1);
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check!(!ne, 0, 0);
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check!(ne, FOO as *const _, 0);
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check!(!eq, FOO as *const _, 0);
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// We want pointers to be equal to themselves, but aren't checking this yet because
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// there are some open questions (e.g. whether function pointers to the same function
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// compare equal, they don't necessarily at runtime).
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// The case tested here should work eventually, but does not work yet.
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check!(!eq, FOO as *const _, FOO as *const _);
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check!(ne, unsafe { (FOO as *const usize).offset(1) }, 0);
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check!(!eq, unsafe { (FOO as *const usize).offset(1) }, 0);
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check!(ne, unsafe { (FOO as *const usize as *const u8).offset(3) }, 0);
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check!(!eq, unsafe { (FOO as *const usize as *const u8).offset(3) }, 0);
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///////////////////////////////////////////////////////////////////////////////
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// If any of the below start compiling, make sure to add a `check` test for it.
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// These invocations exist as canaries so we don't forget to check that the
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// behaviour of `guaranteed_eq` and `guaranteed_ne` is still correct.
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// All of these try to obtain an out of bounds pointer in some manner. If we
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// can create out of bounds pointers, we can offset a pointer far enough that
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// at runtime it would be zero and at compile-time it would not be zero.
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const _: *const usize = unsafe { (FOO as *const usize).offset(2) };
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const _: *const u8 =
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unsafe { std::ptr::addr_of!((*(FOO as *const usize as *const [u8; 1000]))[999]) };
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//~^ ERROR evaluation of constant value failed
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//~| out-of-bounds
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const _: usize = unsafe { std::mem::transmute::<*const usize, usize>(FOO) + 4 };
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//~^ ERROR any use of this value will cause an error
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//~| unable to turn pointer into raw bytes
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//~| WARN this was previously accepted by the compiler but is being phased out
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const _: usize = unsafe { *std::mem::transmute::<&&usize, &usize>(&FOO) + 4 };
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//~^ ERROR any use of this value will cause an error
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//~| unable to turn pointer into raw bytes
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//~| WARN this was previously accepted by the compiler but is being phased out
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