Rollup merge of rust-lang#62103 - RalfJung:debug-assert, r=alexcrichton

Add debug assertions to write_bytes and copy*

Looks like @nitnelave  went MIA in rust-lang#58783, so I am re-submitting their PR, tweaked just a bit. I took care to preserve commit authorship.

Cc rust-lang#53871

Author: Mark-Simulacrum

Cargo.lock

@@ -25,7 +25,7 @@ dependencies = [
 name = "alloc"
 version = "0.0.0"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "rand 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_xorshift 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -131,7 +131,7 @@ dependencies = [
  "autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "backtrace-sys 0.1.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-demangle 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
@@ -143,7 +143,7 @@ version = "0.1.27"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
@@ -373,7 +373,7 @@ name = "cfg-if"
 version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
 
@@ -502,7 +502,7 @@ dependencies = [
 
 [[package]]
 name = "compiler_builtins"
-version = "0.1.16"
+version = "0.1.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -834,7 +834,7 @@ name = "dlmalloc"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
@@ -1008,7 +1008,7 @@ name = "fortanix-sgx-abi"
 version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
 
@@ -1199,7 +1199,7 @@ name = "hashbrown"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-alloc 1.0.0",
  "rustc-std-workspace-core 1.0.0",
 ]
@@ -2066,7 +2066,7 @@ dependencies = [
 name = "panic_abort"
 version = "0.0.0"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -2077,7 +2077,7 @@ version = "0.0.0"
 dependencies = [
  "alloc 0.0.0",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "unwind 0.0.0",
@@ -2263,7 +2263,7 @@ name = "profiler_builtins"
 version = "0.0.0"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -2835,7 +2835,7 @@ name = "rustc-demangle"
 version = "0.1.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
 
@@ -2941,7 +2941,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3160,7 +3160,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3223,7 +3223,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3341,7 +3341,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3648,7 +3648,7 @@ dependencies = [
  "backtrace 0.3.29 (registry+https://github.com/rust-lang/crates.io-index)",
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "dlmalloc 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fortanix-sgx-abi 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4309,7 +4309,7 @@ version = "0.0.0"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -4527,7 +4527,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum colored 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b0aa3473e85a3161b59845d6096b289bb577874cafeaf75ea1b1beaa6572c7fc"
 "checksum commoncrypto 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d056a8586ba25a1e4d61cb090900e495952c7886786fc55f909ab2f819b69007"
 "checksum commoncrypto-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1fed34f46747aa73dfaa578069fd8279d2818ade2b55f38f22a9401c7f4083e2"
-"checksum compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)" = "e79ed19793c99771b386d76e08c3419409bb3d418b81a8b8afc73524247461cf"
+"checksum compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)" = "ad9b4731b9e701aefe9e6bd1e9173f30526661508f9aaadaa5caec25ddf95585"
 "checksum compiletest_rs 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)" = "f40ecc9332b68270998995c00f8051ee856121764a0d3230e64c9efd059d27b6"
 "checksum constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8ff012e225ce166d4422e0e78419d901719760f62ae2b7969ca6b564d1b54a9e"
 "checksum core-foundation 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "4e2640d6d0bf22e82bed1b73c6aef8d5dd31e5abe6666c57e6d45e2649f4f887"

src/libcore/intrinsics.rs

@@ -36,6 +36,8 @@
             issue = "0")]
 #![allow(missing_docs)]
 
+use crate::mem;
+
 #[stable(feature = "drop_in_place", since = "1.8.0")]
 #[rustc_deprecated(reason = "no longer an intrinsic - use `ptr::drop_in_place` directly",
                    since = "1.18.0")]
@@ -1323,6 +1325,26 @@ extern "rust-intrinsic" {
 // (`transmute` also falls into this category, but it cannot be wrapped due to the
 // check that `T` and `U` have the same size.)
 
+/// Checks whether `ptr` is properly aligned with respect to
+/// `align_of::<T>()`.
+pub(crate) fn is_aligned_and_not_null<T>(ptr: *const T) -> bool {
+    !ptr.is_null() && ptr as usize % mem::align_of::<T>() == 0
+}
+
+/// Checks whether the regions of memory starting at `src` and `dst` of size
+/// `count * size_of::<T>()` overlap.
+fn overlaps<T>(src: *const T, dst: *const T, count: usize) -> bool {
+    let src_usize = src as usize;
+    let dst_usize = dst as usize;
+    let size = mem::size_of::<T>().checked_mul(count).unwrap();
+    let diff = if src_usize > dst_usize {
+        src_usize - dst_usize
+    } else {
+        dst_usize - src_usize
+    };
+    size > diff
+}
+
 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
 /// and destination must *not* overlap.
 ///
@@ -1412,7 +1434,11 @@ pub unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize) {
     extern "rust-intrinsic" {
         fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
     }
-    copy_nonoverlapping(src, dst, count);
+
+    debug_assert!(is_aligned_and_not_null(src), "attempt to copy from unaligned or null pointer");
+    debug_assert!(is_aligned_and_not_null(dst), "attempt to copy to unaligned or null pointer");
+    debug_assert!(!overlaps(src, dst, count), "attempt to copy to overlapping memory");
+    copy_nonoverlapping(src, dst, count)
 }
 
 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
@@ -1472,6 +1498,9 @@ pub unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
     extern "rust-intrinsic" {
         fn copy<T>(src: *const T, dst: *mut T, count: usize);
     }
+
+    debug_assert!(is_aligned_and_not_null(src), "attempt to copy from unaligned or null pointer");
+    debug_assert!(is_aligned_and_not_null(dst), "attempt to copy to unaligned or null pointer");
     copy(src, dst, count)
 }
 
@@ -1553,5 +1582,7 @@ pub unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
     extern "rust-intrinsic" {
         fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
     }
+
+    debug_assert!(is_aligned_and_not_null(dst), "attempt to write to unaligned or null pointer");
     write_bytes(dst, val, count)
 }

src/libcore/slice/mod.rs

@@ -25,7 +25,7 @@
 use crate::cmp::Ordering::{self, Less, Equal, Greater};
 use crate::cmp;
 use crate::fmt;
-use crate::intrinsics::{assume, exact_div, unchecked_sub};
+use crate::intrinsics::{assume, exact_div, unchecked_sub, is_aligned_and_not_null};
 use crate::isize;
 use crate::iter::*;
 use crate::ops::{FnMut, Try, self};
@@ -5228,7 +5228,7 @@ unsafe impl<'a, T> TrustedRandomAccess for RChunksExactMut<'a, T> {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
-    debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
+    debug_assert!(is_aligned_and_not_null(data), "attempt to create unaligned or null slice");
     debug_assert!(mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize,
                   "attempt to create slice covering half the address space");
     &*ptr::slice_from_raw_parts(data, len)
@@ -5249,7 +5249,7 @@ pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] {
-    debug_assert!(data as usize % mem::align_of::<T>() == 0, "attempt to create unaligned slice");
+    debug_assert!(is_aligned_and_not_null(data), "attempt to create unaligned or null slice");
     debug_assert!(mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize,
                   "attempt to create slice covering half the address space");
     &mut *ptr::slice_from_raw_parts_mut(data, len)

src/test/codegen/issue-45222.rs

@@ -1,4 +1,5 @@
 // compile-flags: -O
+// ignore-debug: the debug assertions get in the way
 
 #![crate_type = "lib"]
 

src/test/codegen/issue-45466.rs

@@ -1,4 +1,5 @@
 // compile-flags: -O
+// ignore-debug: the debug assertions get in the way
 
 #![crate_type="rlib"]
 

src/test/codegen/swap-small-types.rs

@@ -1,5 +1,6 @@
 // compile-flags: -O
 // only-x86_64
+// ignore-debug: the debug assertions get in the way
 
 #![crate_type = "lib"]