Auto merge of #129658 - saethlin:spare-a-crumb, r=<try>

Add some track_caller info to precondition panics

Currently, when you encounter a precondition check, you'll always get the caller location of the implementation of the precondition checks. But with this PR, you'll be told the location of the invalid call. Which is useful.

I thought of this while looking at #129642 (comment).

The changes to `tests/ui/const*` happen because the const-eval interpreter skips `#[track_caller]` frames in its backtraces.

The perf implications of this are:
* Increased debug binary sizes. The caller_location implementation requires that the additional data we want to display here be stored in const allocations, which are deduplicated but not across crates. There is no impact on optimized build sizes. The panic path and the caller location data get optimized out.
* The compile time hit to opt-incr-patched bitmaps happens because the patch changes the line number of some function calls with precondition checks, causing us to go from 0 dirty CGUs to 1 dirty CGU.
* The other compile time hits are marginal but real, and due to doing a handful of new queries. Adding more useful data isn't completely free.

Author: bors

library/core/src/alloc/layout.rs

@@ -126,6 +126,7 @@ impl Layout {
     #[rustc_const_stable(feature = "const_alloc_layout_unchecked", since = "1.36.0")]
     #[must_use]
     #[inline]
+    #[track_caller]
     pub const unsafe fn from_size_align_unchecked(size: usize, align: usize) -> Self {
         assert_unsafe_precondition!(
             check_library_ub,

library/core/src/ascii/ascii_char.rs

@@ -503,6 +503,7 @@ impl AsciiChar {
     /// something useful. It might be tightened before stabilization.)
     #[unstable(feature = "ascii_char", issue = "110998")]
     #[inline]
+    #[track_caller]
     pub const unsafe fn digit_unchecked(d: u8) -> Self {
         assert_unsafe_precondition!(
             check_language_ub,

library/core/src/char/convert.rs

@@ -22,6 +22,7 @@ pub(super) const fn from_u32(i: u32) -> Option<char> {
 #[inline]
 #[must_use]
 #[allow(unnecessary_transmutes)]
+#[track_caller]
 pub(super) const unsafe fn from_u32_unchecked(i: u32) -> char {
     // SAFETY: the caller must guarantee that `i` is a valid char value.
     unsafe {

library/core/src/hint.rs

@@ -98,7 +98,7 @@ use crate::{intrinsics, ub_checks};
 #[inline]
 #[stable(feature = "unreachable", since = "1.27.0")]
 #[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 pub const unsafe fn unreachable_unchecked() -> ! {
     ub_checks::assert_unsafe_precondition!(
         check_language_ub,

library/core/src/intrinsics/mod.rs

@@ -2634,7 +2634,7 @@ pub const fn three_way_compare<T: Copy>(lhs: T, rhss: T) -> crate::cmp::Ordering
 #[rustc_const_unstable(feature = "disjoint_bitor", issue = "135758")]
 #[rustc_nounwind]
 #[rustc_intrinsic]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 #[miri::intrinsic_fallback_is_spec] // the fallbacks all `assume` to tell Miri
 pub const unsafe fn disjoint_bitor<T: ~const fallback::DisjointBitOr>(a: T, b: T) -> T {
     // SAFETY: same preconditions as this function.

library/core/src/num/int_macros.rs

@@ -555,7 +555,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_add(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -705,7 +705,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_sub(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -855,7 +855,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_mul(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -1199,7 +1199,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_neg(self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -1327,7 +1327,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_shl(self, rhs: u32) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -1448,7 +1448,7 @@ macro_rules! int_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,

library/core/src/num/nonzero.rs

@@ -388,6 +388,7 @@ where
     #[rustc_const_stable(feature = "nonzero", since = "1.28.0")]
     #[must_use]
     #[inline]
+    #[track_caller]
     pub const unsafe fn new_unchecked(n: T) -> Self {
         match Self::new(n) {
             Some(n) => n,
@@ -428,6 +429,7 @@ where
     #[unstable(feature = "nonzero_from_mut", issue = "106290")]
     #[must_use]
     #[inline]
+    #[track_caller]
     pub unsafe fn from_mut_unchecked(n: &mut T) -> &mut Self {
         match Self::from_mut(n) {
             Some(n) => n,

library/core/src/num/uint_macros.rs

@@ -601,7 +601,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_add(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -791,7 +791,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_sub(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -974,7 +974,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_mul(self, rhs: Self) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -1588,7 +1588,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_shl(self, rhs: u32) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,
@@ -1709,7 +1709,7 @@ macro_rules! uint_impl {
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+        #[track_caller]
         pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self {
             assert_unsafe_precondition!(
                 check_language_ub,

library/core/src/ops/index_range.rs

@@ -19,6 +19,7 @@ impl IndexRange {
     /// # Safety
     /// - `start <= end`
     #[inline]
+    #[track_caller]
     pub(crate) const unsafe fn new_unchecked(start: usize, end: usize) -> Self {
         ub_checks::assert_unsafe_precondition!(
             check_library_ub,

library/core/src/ptr/alignment.rs

@@ -73,6 +73,7 @@ impl Alignment {
     /// It must *not* be zero.
     #[unstable(feature = "ptr_alignment_type", issue = "102070")]
     #[inline]
+    #[track_caller]
     pub const unsafe fn new_unchecked(align: usize) -> Self {
         assert_unsafe_precondition!(
             check_language_ub,

library/core/src/ptr/const_ptr.rs

@@ -444,7 +444,7 @@ impl<T: ?Sized> *const T {
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
     #[inline(always)]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn offset(self, count: isize) -> *const T
     where
         T: Sized,
@@ -497,7 +497,7 @@ impl<T: ?Sized> *const T {
     #[inline(always)]
     #[stable(feature = "pointer_byte_offsets", since = "1.75.0")]
     #[rustc_const_stable(feature = "const_pointer_byte_offsets", since = "1.75.0")]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn byte_offset(self, count: isize) -> Self {
         // SAFETY: the caller must uphold the safety contract for `offset`.
         unsafe { self.cast::<u8>().offset(count).with_metadata_of(self) }
@@ -796,7 +796,7 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "ptr_sub_ptr", since = "1.87.0")]
     #[rustc_const_stable(feature = "const_ptr_sub_ptr", since = "1.87.0")]
     #[inline]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn offset_from_unsigned(self, origin: *const T) -> usize
     where
         T: Sized,
@@ -841,7 +841,7 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "ptr_sub_ptr", since = "1.87.0")]
     #[rustc_const_stable(feature = "const_ptr_sub_ptr", since = "1.87.0")]
     #[inline]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn byte_offset_from_unsigned<U: ?Sized>(self, origin: *const U) -> usize {
         // SAFETY: the caller must uphold the safety contract for `offset_from_unsigned`.
         unsafe { self.cast::<u8>().offset_from_unsigned(origin.cast::<u8>()) }
@@ -955,7 +955,7 @@ impl<T: ?Sized> *const T {
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
     #[inline(always)]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn add(self, count: usize) -> Self
     where
         T: Sized,
@@ -1007,7 +1007,7 @@ impl<T: ?Sized> *const T {
     #[inline(always)]
     #[stable(feature = "pointer_byte_offsets", since = "1.75.0")]
     #[rustc_const_stable(feature = "const_pointer_byte_offsets", since = "1.75.0")]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn byte_add(self, count: usize) -> Self {
         // SAFETY: the caller must uphold the safety contract for `add`.
         unsafe { self.cast::<u8>().add(count).with_metadata_of(self) }
@@ -1061,7 +1061,7 @@ impl<T: ?Sized> *const T {
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
     #[inline(always)]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn sub(self, count: usize) -> Self
     where
         T: Sized,
@@ -1119,7 +1119,7 @@ impl<T: ?Sized> *const T {
     #[inline(always)]
     #[stable(feature = "pointer_byte_offsets", since = "1.75.0")]
     #[rustc_const_stable(feature = "const_pointer_byte_offsets", since = "1.75.0")]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn byte_sub(self, count: usize) -> Self {
         // SAFETY: the caller must uphold the safety contract for `sub`.
         unsafe { self.cast::<u8>().sub(count).with_metadata_of(self) }
@@ -1292,7 +1292,7 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_stable(feature = "const_ptr_read", since = "1.71.0")]
     #[inline]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn read(self) -> T
     where
         T: Sized,
@@ -1313,7 +1313,7 @@ impl<T: ?Sized> *const T {
     /// [`ptr::read_volatile`]: crate::ptr::read_volatile()
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[inline]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub unsafe fn read_volatile(self) -> T
     where
         T: Sized,
@@ -1333,7 +1333,7 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[rustc_const_stable(feature = "const_ptr_read", since = "1.71.0")]
     #[inline]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn read_unaligned(self) -> T
     where
         T: Sized,
@@ -1353,7 +1353,7 @@ impl<T: ?Sized> *const T {
     #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[inline]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn copy_to(self, dest: *mut T, count: usize)
     where
         T: Sized,
@@ -1373,7 +1373,7 @@ impl<T: ?Sized> *const T {
     #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.83.0")]
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[inline]
-    #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+    #[track_caller]
     pub const unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
     where
         T: Sized,

library/core/src/ptr/mod.rs

@@ -1377,6 +1377,7 @@ pub const unsafe fn swap<T>(x: *mut T, y: *mut T) {
 #[rustc_const_stable(feature = "const_swap_nonoverlapping", since = "1.88.0")]
 #[rustc_diagnostic_item = "ptr_swap_nonoverlapping"]
 #[rustc_allow_const_fn_unstable(const_eval_select)] // both implementations behave the same
+#[track_caller]
 pub const unsafe fn swap_nonoverlapping<T>(x: *mut T, y: *mut T, count: usize) {
     ub_checks::assert_unsafe_precondition!(
         check_library_ub,
@@ -1557,6 +1558,7 @@ unsafe fn swap_nonoverlapping_bytes(x: *mut u8, y: *mut u8, bytes: NonZero<usize
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_replace", since = "1.83.0")]
 #[rustc_diagnostic_item = "ptr_replace"]
+#[track_caller]
 pub const unsafe fn replace<T>(dst: *mut T, src: T) -> T {
     // SAFETY: the caller must guarantee that `dst` is valid to be
     // cast to a mutable reference (valid for writes, aligned, initialized),
@@ -1684,7 +1686,7 @@ pub const unsafe fn replace<T>(dst: *mut T, src: T) -> T {
 #[inline]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_ptr_read", since = "1.71.0")]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 #[rustc_diagnostic_item = "ptr_read"]
 pub const unsafe fn read<T>(src: *const T) -> T {
     // It would be semantically correct to implement this via `copy_nonoverlapping`
@@ -1802,7 +1804,7 @@ pub const unsafe fn read<T>(src: *const T) -> T {
 #[inline]
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
 #[rustc_const_stable(feature = "const_ptr_read", since = "1.71.0")]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 #[rustc_diagnostic_item = "ptr_read_unaligned"]
 pub const unsafe fn read_unaligned<T>(src: *const T) -> T {
     let mut tmp = MaybeUninit::<T>::uninit();
@@ -1901,7 +1903,7 @@ pub const unsafe fn read_unaligned<T>(src: *const T) -> T {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
 #[rustc_diagnostic_item = "ptr_write"]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 pub const unsafe fn write<T>(dst: *mut T, src: T) {
     // Semantically, it would be fine for this to be implemented as a
     // `copy_nonoverlapping` and appropriate drop suppression of `src`.
@@ -2005,7 +2007,7 @@ pub const unsafe fn write<T>(dst: *mut T, src: T) {
 #[stable(feature = "ptr_unaligned", since = "1.17.0")]
 #[rustc_const_stable(feature = "const_ptr_write", since = "1.83.0")]
 #[rustc_diagnostic_item = "ptr_write_unaligned"]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 pub const unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
     // SAFETY: the caller must guarantee that `dst` is valid for writes.
     // `dst` cannot overlap `src` because the caller has mutable access
@@ -2079,7 +2081,7 @@ pub const unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
 /// ```
 #[inline]
 #[stable(feature = "volatile", since = "1.9.0")]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 #[rustc_diagnostic_item = "ptr_read_volatile"]
 pub unsafe fn read_volatile<T>(src: *const T) -> T {
     // SAFETY: the caller must uphold the safety contract for `volatile_load`.
@@ -2160,7 +2162,7 @@ pub unsafe fn read_volatile<T>(src: *const T) -> T {
 #[inline]
 #[stable(feature = "volatile", since = "1.9.0")]
 #[rustc_diagnostic_item = "ptr_write_volatile"]
-#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
+#[track_caller]
 pub unsafe fn write_volatile<T>(dst: *mut T, src: T) {
     // SAFETY: the caller must uphold the safety contract for `volatile_store`.
     unsafe {