Rollup merge of #143327 - RalfJung:miri-type-validity-error, r=oli-obk

miri: improve errors for type validity assertion failures

Miri has pretty nice errors for type validity violations, printing which field in the type the problem occurs at and so on.

However, we don't see these errors when using e.g. `mem::zeroed` as that uses `assert_zero_valid` to bail out before Miri can detect the UB.

Similar to what we did with `@saethlin's` UB checks, I think we should disable such language UB checks in Miri so that we can get better error messages. If we go for this we should probably say this in the intrinsic docs as well so that people don't think they can rely on these intrinsics catching anything.

Furthermore, I slightly changed `MaybeUninit::assume_init` so that the `.value` field does not show up in error messages any more.

`@rust-lang/miri` what do you think?

Author: matthiaskrgr

src/intrinsics/mod.rs

@@ -457,6 +457,10 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 throw_machine_stop!(TerminationInfo::Abort(format!("trace/breakpoint trap")))
             }
 
+            "assert_inhabited" | "assert_zero_valid" | "assert_mem_uninitialized_valid" => {
+                // Make these a NOP, so we get the better Miri-native error messages.
+            }
+
             _ => return interp_ok(EmulateItemResult::NotSupported),
         }
 

tests/fail-dep/libc/libc-read-and-uninit-premature-eof.rs

@@ -20,7 +20,7 @@ fn main() {
         let mut buf: MaybeUninit<[u8; 4]> = std::mem::MaybeUninit::uninit();
         // Read 4 bytes from a 3-byte file.
         assert_eq!(libc::read(fd, buf.as_mut_ptr().cast::<std::ffi::c_void>(), 4), 3);
-        buf.assume_init(); //~ERROR: Undefined Behavior: constructing invalid value at .value[3]: encountered uninitialized memory, but expected an integer
+        buf.assume_init(); //~ERROR: encountered uninitialized memory, but expected an integer
         assert_eq!(libc::close(fd), 0);
     }
     remove_file(&path).unwrap();

tests/fail-dep/libc/libc-read-and-uninit-premature-eof.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: constructing invalid value at .value[3]: encountered uninitialized memory, but expected an integer
+error: Undefined Behavior: constructing invalid value at [3]: encountered uninitialized memory, but expected an integer
   --> tests/fail-dep/libc/libc-read-and-uninit-premature-eof.rs:LL:CC
    |
-LL | ...   buf.assume_init();
-   |       ^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
+LL |         buf.assume_init();
+   |         ^^^^^^^^^^^^^^^^^ 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

tests/fail/intrinsics/uninit_uninhabited_type.rs

@@ -1,11 +1,6 @@
-//@normalize-stderr-test: "\|.*::abort\(\).*" -> "| ABORT()"
-//@normalize-stderr-test: "\| +\^+" -> "| ^"
-//@normalize-stderr-test: "\n +[0-9]+:[^\n]+" -> ""
-//@normalize-stderr-test: "\n +at [^\n]+" -> ""
-//@error-in-other-file: aborted execution
 #![feature(never_type)]
 
 #[allow(deprecated, invalid_value)]
 fn main() {
-    let _ = unsafe { std::mem::uninitialized::<!>() };
+    let _ = unsafe { std::mem::uninitialized::<!>() }; //~ERROR: constructing invalid value
 }

tests/fail/intrinsics/uninit_uninhabited_type.stderr

@@ -1,27 +1,13 @@
-
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
-aborted execution: attempted to instantiate uninhabited type `!`
-note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
-note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
-thread caused non-unwinding panic. aborting.
-error: abnormal termination: the program aborted execution
-  --> RUSTLIB/std/src/sys/pal/PLATFORM/mod.rs:LL:CC
-   |
-LL | ABORT()
-   | ^ abnormal termination occurred here
-   |
-   = note: BACKTRACE:
-   = note: inside `std::sys::pal::PLATFORM::abort_internal` at RUSTLIB/std/src/sys/pal/PLATFORM/mod.rs:LL:CC
-   = note: inside `std::panicking::rust_panic_with_hook` at RUSTLIB/std/src/panicking.rs:LL:CC
-   = note: inside closure at RUSTLIB/std/src/panicking.rs:LL:CC
-   = note: inside `std::sys::backtrace::__rust_end_short_backtrace::<{closure@std::panicking::begin_panic_handler::{closure#0}}, !>` at RUSTLIB/std/src/sys/backtrace.rs:LL:CC
-   = note: inside `std::panicking::begin_panic_handler` at RUSTLIB/std/src/panicking.rs:LL:CC
-   = note: inside `core::panicking::panic_nounwind` at RUSTLIB/core/src/panicking.rs:LL:CC
-note: inside `main`
+error: Undefined Behavior: constructing invalid value: encountered a value of the never type `!`
   --> tests/fail/intrinsics/uninit_uninhabited_type.rs:LL:CC
    |
 LL |     let _ = unsafe { std::mem::uninitialized::<!>() };
-   | ^
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 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
+   = note: BACKTRACE:
+   = note: inside `main` at tests/fail/intrinsics/uninit_uninhabited_type.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

tests/fail/intrinsics/zero_fn_ptr.rs

@@ -1,10 +1,4 @@
-//@normalize-stderr-test: "\|.*::abort\(\).*" -> "| ABORT()"
-//@normalize-stderr-test: "\| +\^+" -> "| ^"
-//@normalize-stderr-test: "\n +[0-9]+:[^\n]+" -> ""
-//@normalize-stderr-test: "\n +at [^\n]+" -> ""
-//@error-in-other-file: aborted execution
-
 #[allow(deprecated, invalid_value)]
 fn main() {
-    let _ = unsafe { std::mem::zeroed::<fn()>() };
+    let _ = unsafe { std::mem::zeroed::<fn()>() }; //~ERROR: constructing invalid value
 }

tests/fail/intrinsics/zero_fn_ptr.stderr

@@ -1,27 +1,13 @@
-
-thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
-aborted execution: attempted to zero-initialize type `fn()`, which is invalid
-note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
-note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
-thread caused non-unwinding panic. aborting.
-error: abnormal termination: the program aborted execution
-  --> RUSTLIB/std/src/sys/pal/PLATFORM/mod.rs:LL:CC
-   |
-LL | ABORT()
-   | ^ abnormal termination occurred here
-   |
-   = note: BACKTRACE:
-   = note: inside `std::sys::pal::PLATFORM::abort_internal` at RUSTLIB/std/src/sys/pal/PLATFORM/mod.rs:LL:CC
-   = note: inside `std::panicking::rust_panic_with_hook` at RUSTLIB/std/src/panicking.rs:LL:CC
-   = note: inside closure at RUSTLIB/std/src/panicking.rs:LL:CC
-   = note: inside `std::sys::backtrace::__rust_end_short_backtrace::<{closure@std::panicking::begin_panic_handler::{closure#0}}, !>` at RUSTLIB/std/src/sys/backtrace.rs:LL:CC
-   = note: inside `std::panicking::begin_panic_handler` at RUSTLIB/std/src/panicking.rs:LL:CC
-   = note: inside `core::panicking::panic_nounwind` at RUSTLIB/core/src/panicking.rs:LL:CC
-note: inside `main`
+error: Undefined Behavior: constructing invalid value: encountered a null function pointer
   --> tests/fail/intrinsics/zero_fn_ptr.rs:LL:CC
    |
 LL |     let _ = unsafe { std::mem::zeroed::<fn()>() };
-   | ^
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^ 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
+   = note: BACKTRACE:
+   = note: inside `main` at tests/fail/intrinsics/zero_fn_ptr.rs:LL:CC
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

tests/fail/validity/uninit_float.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: constructing invalid value at .value[0]: encountered uninitialized memory, but expected a floating point number
+error: Undefined Behavior: constructing invalid value at [0]: encountered uninitialized memory, but expected a floating point number
   --> tests/fail/validity/uninit_float.rs:LL:CC
    |
 LL |     let _val: [f32; 1] = unsafe { std::mem::uninitialized() };

tests/fail/validity/uninit_integer.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: constructing invalid value at .value[0]: encountered uninitialized memory, but expected an integer
+error: Undefined Behavior: constructing invalid value at [0]: encountered uninitialized memory, but expected an integer
   --> tests/fail/validity/uninit_integer.rs:LL:CC
    |
 LL |     let _val = unsafe { std::mem::MaybeUninit::<[usize; 1]>::uninit().assume_init() };

tests/fail/validity/uninit_raw_ptr.stderr

@@ -1,4 +1,4 @@
-error: Undefined Behavior: constructing invalid value at .value[0]: encountered uninitialized memory, but expected a raw pointer
+error: Undefined Behavior: constructing invalid value at [0]: encountered uninitialized memory, but expected a raw pointer
   --> tests/fail/validity/uninit_raw_ptr.rs:LL:CC
    |
 LL |     let _val = unsafe { std::mem::MaybeUninit::<[*const u8; 1]>::uninit().assume_init() };