rust/tests/run-pass/strings.rs
2022-04-01 14:10:24 -04:00

64 lines
2.2 KiB
Rust

// compile-flags: -Zmiri-strict-provenance -Zmiri-check-number-validity
fn empty() -> &'static str {
""
}
fn hello() -> &'static str {
"Hello, world!"
}
fn hello_bytes() -> &'static [u8; 13] {
b"Hello, world!"
}
fn hello_bytes_fat() -> &'static [u8] {
b"Hello, world!"
}
fn fat_pointer_on_32_bit() {
Some(5).expect("foo");
}
fn str_indexing() {
let mut x = "Hello".to_string();
let _v = &mut x[..3]; // Test IndexMut on String.
}
fn unique_aliasing() {
// This is a regression test for the aliasing rules of a `Unique<T>` pointer.
// At the time of writing this test case, Miri does not treat `Unique<T>`
// pointers as a special case, these are treated like any other raw pointer.
// However, there are existing Github issues which may lead to `Unique<T>`
// becoming a special case through asserting unique ownership over the pointee:
// - https://github.com/rust-lang/unsafe-code-guidelines/issues/258
// - https://github.com/rust-lang/unsafe-code-guidelines/issues/262
// Below, the calls to `String::remove` and `String::insert[_str]` follow
// code paths that would trigger undefined behavior in case `Unique<T>`
// would ever assert semantic ownership over the pointee. Internally,
// these methods call `self.vec.as_ptr()` and `self.vec.as_mut_ptr()` on
// the vector of bytes that are backing the `String`. That `Vec<u8>` holds a
// `Unique<u8>` internally. The second call to `Vec::as_mut_ptr(&mut self)`
// would then invalidate the pointers derived from `Vec::as_ptr(&self)`.
// Note that as long as `Unique<T>` is treated like any other raw pointer,
// this test case should pass. It is merely here as a canary test for
// potential future undefined behavior.
let mut x = String::from("Hello");
assert_eq!(x.remove(0), 'H');
x.insert(0, 'H');
assert_eq!(x, "Hello");
x.insert_str(x.len(), ", world!");
assert_eq!(x, "Hello, world!");
}
fn main() {
assert_eq!(empty(), "");
assert_eq!(hello(), "Hello, world!");
assert_eq!(hello_bytes(), b"Hello, world!");
assert_eq!(hello_bytes_fat(), b"Hello, world!");
fat_pointer_on_32_bit(); // Should run without crashing.
str_indexing();
unique_aliasing();
}