Rollup merge of #128277 - RalfJung:offset_from_wildcard, r=oli-obk

miri: fix offset_from behavior on wildcard pointers

offset_from wouldn't behave correctly when the "end" pointer was a wildcard pointer (result of an int2ptr cast) just at the end of the allocation. Fix that by expressing the "same allocation" check in terms of two `check_ptr_access_signed` instead of something specific to offset_from, which is both more canonical and works better with wildcard pointers.

The second commit just improves diagnostics: I wanted the "pointer is dangling (has no provenance)" message to say how many bytes of memory it expected to see (since if it were 0 bytes, this would actually be legal, so it's good to tell the user that it's not 0 bytes). And then I was annoying that the error looks so different for when you deref a dangling pointer vs an out-of-bounds pointer so I made them more similar.

Fixes #3767

Author: matthiaskrgr

tests/fail-dep/libc/affinity.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: memory access failed: ALLOC has size 128, so pointer to 129 bytes starting at offset 0 is out-of-bounds
+error: Undefined Behavior: memory access failed: expected a pointer to 129 bytes of memory, but got ALLOC and there are only 128 bytes starting at that pointer
   --> $DIR/affinity.rs:LL:CC
    |
 LL |     let err = unsafe { sched_setaffinity(PID, size_of::<cpu_set_t>() + 1, &cpuset) };
-   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: ALLOC has size 128, so pointer to 129 bytes starting at offset 0 is out-of-bounds
+   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ memory access failed: expected a pointer to 129 bytes of memory, but got ALLOC and there are only 128 bytes starting at that pointer
    |
    = 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

tests/fail-dep/libc/memchr_null.rs

@@ -3,6 +3,6 @@ use std::ptr;
 // null is explicitly called out as UB in the C docs.
 fn main() {
     unsafe {
-        libc::memchr(ptr::null(), 0, 0); //~ERROR: dangling
+        libc::memchr(ptr::null(), 0, 0); //~ERROR: null pointer
     }
 }

tests/fail-dep/libc/memchr_null.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: out-of-bounds pointer use: null pointer is a dangling pointer (it has no provenance)
+error: Undefined Behavior: out-of-bounds pointer use: expected a pointer to some allocation, but got a null pointer
   --> $DIR/memchr_null.rs:LL:CC
    |
 LL |         libc::memchr(ptr::null(), 0, 0);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: null pointer is a dangling pointer (it has no provenance)
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: expected a pointer to some allocation, but got a null pointer
    |
    = 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

tests/fail-dep/libc/memcmp_null.rs

@@ -3,6 +3,6 @@ use std::ptr;
 // null is explicitly called out as UB in the C docs.
 fn main() {
     unsafe {
-        libc::memcmp(ptr::null(), ptr::null(), 0); //~ERROR: dangling
+        libc::memcmp(ptr::null(), ptr::null(), 0); //~ERROR: null pointer
     }
 }

tests/fail-dep/libc/memcmp_null.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: out-of-bounds pointer use: null pointer is a dangling pointer (it has no provenance)
+error: Undefined Behavior: out-of-bounds pointer use: expected a pointer to some allocation, but got a null pointer
   --> $DIR/memcmp_null.rs:LL:CC
    |
 LL |         libc::memcmp(ptr::null(), ptr::null(), 0);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: null pointer is a dangling pointer (it has no provenance)
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: expected a pointer to some allocation, but got a null pointer
    |
    = 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

tests/fail-dep/libc/memcmp_zero.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: out-of-bounds pointer use: 0x2a[noalloc] is a dangling pointer (it has no provenance)
+error: Undefined Behavior: out-of-bounds pointer use: expected a pointer to some allocation, but got 0x2a[noalloc] which is a dangling pointer (it has no provenance)
   --> $DIR/memcmp_zero.rs:LL:CC
    |
 LL |         libc::memcmp(ptr.cast(), ptr.cast(), 0);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: 0x2a[noalloc] is a dangling pointer (it has no provenance)
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: expected a pointer to some allocation, but got 0x2a[noalloc] which is a dangling pointer (it has no provenance)
    |
    = 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

tests/fail-dep/libc/memcpy_zero.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: out-of-bounds pointer use: 0x17[noalloc] is a dangling pointer (it has no provenance)
+error: Undefined Behavior: out-of-bounds pointer use: expected a pointer to some allocation, but got 0x17[noalloc] which is a dangling pointer (it has no provenance)
   --> $DIR/memcpy_zero.rs:LL:CC
    |
 LL |         libc::memcpy(to.cast(), from.cast(), 0);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: 0x17[noalloc] is a dangling pointer (it has no provenance)
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: expected a pointer to some allocation, but got 0x17[noalloc] which is a dangling pointer (it has no provenance)
    |
    = 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

tests/fail-dep/libc/memrchr_null.rs

@@ -6,6 +6,6 @@ use std::ptr;
 // null is explicitly called out as UB in the C docs.
 fn main() {
     unsafe {
-        libc::memrchr(ptr::null(), 0, 0); //~ERROR: dangling
+        libc::memrchr(ptr::null(), 0, 0); //~ERROR: null pointer
     }
 }

tests/fail-dep/libc/memrchr_null.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: out-of-bounds pointer use: null pointer is a dangling pointer (it has no provenance)
+error: Undefined Behavior: out-of-bounds pointer use: expected a pointer to some allocation, but got a null pointer
   --> $DIR/memrchr_null.rs:LL:CC
    |
 LL |         libc::memrchr(ptr::null(), 0, 0);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: null pointer is a dangling pointer (it has no provenance)
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds pointer use: expected a pointer to some allocation, but got a null pointer
    |
    = 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

tests/fail/both_borrows/issue-miri-1050-1.rs

@@ -1,6 +1,6 @@
 //@revisions: stack tree
 //@[tree]compile-flags: -Zmiri-tree-borrows
-//@error-in-other-file: pointer to 4 bytes starting at offset 0 is out-of-bounds
+//@error-in-other-file: expected a pointer to 4 bytes of memory
 
 fn main() {
     unsafe {