miri: fix out-of-bounds error for ptrs with negative offsets

4 files changed, 53 insertions, 0 deletions

diff --git a/src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.rs b/src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.rs
new file mode 100644
index 00000000000..107a3db91d8
--- /dev/null
+++ b/src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.rs
@@ -0,0 +1,6 @@
+fn main() {
+    let v: Vec<u16> = vec![1, 2];
+    // This read is also misaligned. We make sure that the OOB message has priority.
+    let x = unsafe { *v.as_ptr().wrapping_byte_sub(5) }; //~ ERROR: before the beginning of the allocation
+    panic!("this should never print: {}", x);
+}
diff --git a/src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.stderr b/src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.stderr
new file mode 100644
index 00000000000..5c37caa1ebf
--- /dev/null
+++ b/src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.stderr
@@ -0,0 +1,21 @@
+error: Undefined Behavior: memory access failed: attempting to access 2 bytes, but got ALLOC-0x5 which points to before the beginning of the allocation
+  --> tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.rs:LL:CC
+   |
+LL |     let x = unsafe { *v.as_ptr().wrapping_byte_sub(5) };
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+help: ALLOC was allocated here:
+  --> tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.rs:LL:CC
+   |
+LL |     let v: Vec<u16> = vec![1, 2];
+   |                       ^^^^^^^^^^
+   = note: BACKTRACE (of the first span):
+   = note: inside `main` at tests/fail/dangling_pointers/out_of_bounds_read_neg_offset.rs:LL:CC
+   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+
diff --git a/src/tools/miri/tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.rs b/src/tools/miri/tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.rs
new file mode 100644
index 00000000000..0085e2af367
--- /dev/null
+++ b/src/tools/miri/tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.rs
@@ -0,0 +1,6 @@
+fn main() {
+    let v = [0i8; 4];
+    let x = &v as *const i8;
+    let x = unsafe { x.wrapping_offset(-1).offset(-1) }; //~ERROR: before the beginning of the allocation
+    panic!("this should never print: {:?}", x);
+}
diff --git a/src/tools/miri/tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.stderr b/src/tools/miri/tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.stderr
new file mode 100644
index 00000000000..495aaf8d40e
--- /dev/null
+++ b/src/tools/miri/tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.stderr
@@ -0,0 +1,20 @@
+error: Undefined Behavior: in-bounds pointer arithmetic failed: attempting to offset pointer by -1 bytes, but got ALLOC-0x1 which points to before the beginning of the allocation
+  --> tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.rs:LL:CC
+   |
+LL |     let x = unsafe { x.wrapping_offset(-1).offset(-1) };
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+help: ALLOC was allocated here:
+  --> tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.rs:LL:CC
+   |
+LL |     let v = [0i8; 4];
+   |         ^
+   = note: BACKTRACE (of the first span):
+   = note: inside `main` at tests/fail/intrinsics/ptr_offset_out_of_bounds_neg2.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+