Skip to content

Commit

Permalink
Add a bunch of tests for #107975
Browse files Browse the repository at this point in the history
  • Loading branch information
GrigorenkoPV committed Jul 6, 2024
1 parent 3bec617 commit a7c36d1
Show file tree
Hide file tree
Showing 37 changed files with 732 additions and 0 deletions.
22 changes: 22 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/README.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
See https://github.com/rust-lang/rust/issues/107975

Basically, if you have two pointers with the same address but from two different allocations,
the compiler gets confused whether their addresses are equal or not,
resulting in some self-contradictory behavior of the compiled code.

This folder contains some examples.
They all boil down to allocating a variable on the stack, taking its address,
getting rid of the variable, and then doing it all again.
This way we end up with two addresses stored in two `usize`s (`a` and `b`).
The addresses are (probably) equal but (definitely) come from two different allocations.
Logically, we would expect that exactly one of the following options holds true:
1. `a == b`
2. `a != b`
Sadly, the compiler does not always agree.

Due to Rust having at least three meaningfully different ways
to get a variable's address as an `usize`,
each example is provided in three versions, each in the corresponding subfolder:
1. `./as-cast/` for `&v as *const _ as usize`,
2. `./strict-provenance/` for `addr_of!(v).addr()`,
2. `./exposed-provenance/` for `addr_of!(v).expose_provenance()`.
20 changes: 20 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/basic.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
//@ known-bug: #107975
//@ run-pass

fn main() {
let a: usize = {
let v = 0u8;
&v as *const _ as usize
};
let b: usize = {
let v = 0u8;
&v as *const _ as usize
};

// `a` and `b` are not equal.
assert_ne!(a, b);
// But they are the same number.
assert_eq!(format!("{a}"), format!("{b}"));
// And they are equal.
assert_eq!(a, b);
}
21 changes: 21 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/function.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
//@ known-bug: #107975
//@ run-pass

// Based on https://github.com/rust-lang/rust/issues/107975#issuecomment-1434203908

fn f() -> usize {
let v = 0;
&v as *const _ as usize
}

fn main() {
let a = f();
let b = f();

// `a` and `b` are not equal.
assert_ne!(a, b);
// But they are the same number.
assert_eq!(format!("{a}"), format!("{b}"));
// And they are equal.
assert_eq!(a, b);
}
29 changes: 29 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/inline1.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
//@ known-bug: #107975
//@ run-pass
//@ check-run-results
//@ normalize-stdout-test: "\d+" -> "<..>"

// Based on https://github.com/rust-lang/rust/issues/107975#issuecomment-1432161340

#[inline(never)]
fn cmp(a: usize, b: usize) -> bool {
a == b
}

#[inline(always)]
fn cmp_in(a: usize, b: usize) -> bool {
a == b
}

fn main() {
let a = {
let v = 0;
&v as *const _ as usize
};
let b = {
let v = 0;
&v as *const _ as usize
};
println!("{a:?} == {b:?} -> ==: {}, cmp_in: {}, cmp: {}", a == b, cmp_in(a, b), cmp(a, b));
assert_eq!(a.to_string(), b.to_string());
}
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
<..> == <..> -> ==: false, cmp_in: false, cmp: true
29 changes: 29 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/inline2.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
//@ known-bug: #107975
//@ run-pass
//@ check-run-results
//@ normalize-stdout-test: "\d+" -> "<..>"

// Based on https://github.com/rust-lang/rust/issues/107975#issuecomment-1432161340

#[inline(never)]
fn cmp(a: usize, b: usize) -> bool {
a == b
}

#[inline(always)]
fn cmp_in(a: usize, b: usize) -> bool {
a == b
}

fn main() {
let a = {
let v = 0;
&v as *const _ as usize
};
let b = {
let v = 0;
&v as *const _ as usize
};
assert_eq!(a.to_string(), b.to_string());
println!("{a:?} == {b:?} -> ==: {}, cmp_in: {}, cmp: {}", a == b, cmp_in(a, b), cmp(a, b));
}
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
<..> == <..> -> ==: true, cmp_in: true, cmp: true
21 changes: 21 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/print.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,21 @@
//@ known-bug: #107975
//@ run-pass
//@ check-run-results
//@ normalize-stdout-test: "\d+" -> "<..>"

// https://github.com/rust-lang/rust/issues/107975#issuecomment-1430704499

fn main() {
let a = {
let v = 0;
&v as *const _ as usize
};
let b = {
let v = 0;
&v as *const _ as usize
};

println!("{}", a == b); // prints false
println!("{a}"); // or b
println!("{}", a == b); // prints true
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
false
<..>
true
24 changes: 24 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/print3.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
//@ known-bug: #107975
//@ run-pass
//@ check-run-results
//@ normalize-stdout-test: "\d+" -> "<..>"

// https://github.com/rust-lang/rust/issues/107975#issuecomment-1430704499

fn main() {
let a = {
let v = 0;
&v as *const _ as usize
};
let b = {
let v = 0;
&v as *const _ as usize
};

println!("{}", a == b); // false
println!("{}", a == b); // false
let c = a;
println!("{} {} {}", a == b, a == c, b == c); // false true false
println!("{a} {b}");
println!("{} {} {}", a == b, a == c, b == c); // true true true
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
false
false
false true false
<..> <..>
true true true
35 changes: 35 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/segfault.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
//@ known-bug: #107975
//@ run-fail
//@ check-run-results
//@ compile-flags: -Copt-level=3

// This one should segfault.
// I don't know a better way to check for segfault other than
// check that it fails and that the output is empty.

// https://github.com/rust-lang/rust/issues/107975#issuecomment-1431758601

use std::cell::RefCell;

fn main() {
let a = {
let v = 0u8;
&v as *const _ as usize
};
let b = {
let v = 0u8;
&v as *const _ as usize
};
let i = b - a;
let arr = [
RefCell::new(Some(Box::new(1))),
RefCell::new(None),
RefCell::new(None),
RefCell::new(None),
];
assert_ne!(i, 0);
let r = arr[i].borrow();
let r = r.as_ref().unwrap();
*arr[0].borrow_mut() = None;
println!("{}", *r);
}
27 changes: 27 additions & 0 deletions tests/ui/codegen/equal-pointers-unequal/as-cast/zero.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
//@ known-bug: #107975
//@ run-pass

// Derived from https://github.com/rust-lang/rust/issues/107975#issuecomment-1431758601

fn main() {
let a: usize = {
let v = 0u8;
&v as *const _ as usize
};
let b: usize = {
let v = 0u8;
&v as *const _ as usize
};

// So, are `a` and `b` equal?

// Let's check their difference.
let i: usize = a - b;
// It's not zero, which means `a` and `b` are not equal.
assert_ne!(i, 0);
// But it looks like zero...
assert_eq!(i.to_string(), "0");
// ...and now it *is* zero?
assert_eq!(i, 0);
// So `a` and `b` are equal after all?
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
//@ known-bug: #107975
//@ run-pass

#![feature(exposed_provenance)]

use std::ptr::addr_of;

fn main() {
let a: usize = {
let v = 0u8;
addr_of!(v).expose_provenance()
};
let b: usize = {
let v = 0u8;
addr_of!(v).expose_provenance()
};

// `a` and `b` are not equal.
assert_ne!(a, b);
// But they are the same number.
assert_eq!(format!("{a}"), format!("{b}"));
// And they are equal.
assert_eq!(a, b);
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
//@ known-bug: #107975
//@ run-pass

// Based on https://github.com/rust-lang/rust/issues/107975#issuecomment-1434203908

#![feature(exposed_provenance)]

use std::ptr::addr_of;

fn f() -> usize {
let v = 0;
addr_of!(v).expose_provenance()
}

fn main() {
let a = f();
let b = f();

// `a` and `b` are not equal.
assert_ne!(a, b);
// But they are the same number.
assert_eq!(format!("{a}"), format!("{b}"));
// And they are equal.
assert_eq!(a, b);
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
//@ known-bug: #107975
//@ run-pass
//@ check-run-results
//@ normalize-stdout-test: "\d+" -> "<..>"

// Based on https://github.com/rust-lang/rust/issues/107975#issuecomment-1432161340


#![feature(exposed_provenance)]

use std::ptr::addr_of;

#[inline(never)]
fn cmp(a: usize, b: usize) -> bool {
a == b
}

#[inline(always)]
fn cmp_in(a: usize, b: usize) -> bool {
a == b
}

fn main() {
let a = {
let v = 0;
addr_of!(v).expose_provenance()
};
let b = {
let v = 0;
addr_of!(v).expose_provenance()
};
println!("{a:?} == {b:?} -> ==: {}, cmp_in: {}, cmp: {}", a == b, cmp_in(a, b), cmp(a, b));
assert_eq!(a.to_string(), b.to_string());
}
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
<..> == <..> -> ==: false, cmp_in: false, cmp: true
Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
//@ known-bug: #107975
//@ run-pass
//@ check-run-results
//@ normalize-stdout-test: "\d+" -> "<..>"

// Based on https://github.com/rust-lang/rust/issues/107975#issuecomment-1432161340

#![feature(exposed_provenance)]

use std::ptr::addr_of;

#[inline(never)]
fn cmp(a: usize, b: usize) -> bool {
a == b
}

#[inline(always)]
fn cmp_in(a: usize, b: usize) -> bool {
a == b
}

fn main() {
let a = {
let v = 0;
addr_of!(v).expose_provenance()
};
let b = {
let v = 0;
addr_of!(v).expose_provenance()
};
assert_eq!(a.to_string(), b.to_string());
println!("{a:?} == {b:?} -> ==: {}, cmp_in: {}, cmp: {}", a == b, cmp_in(a, b), cmp(a, b));
}
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
<..> == <..> -> ==: true, cmp_in: true, cmp: true
Loading

0 comments on commit a7c36d1

Please sign in to comment.