Rollup merge of rust-lang#105997 - RalfJung:immediate-abort, r=eholk

abort immediately on bad mem::zeroed/uninit

Now that we have non-unwinding panics, let's use them for these assertions. This re-establishes the property that `mem::uninitialized` and `mem::zeroed` will never unwind -- the earlier approach of causing panics here sometimes led to hard-to-debug segfaults when the surrounding code was not able to cope with the unexpected unwinding.

Cc `@bjorn3` I did not touch cranelift but I assume it needs a similar patch. However it has a `codegen_panic` abstraction that I did not want to touch since I didn't know how else it is used.

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -637,7 +637,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         self.set_debug_loc(bx, terminator.source_info);
 
         // Obtain the panic entry point.
-        let (fn_abi, llfn) = common::build_langcall(bx, Some(span), LangItem::PanicNoUnwind);
+        let (fn_abi, llfn) = common::build_langcall(bx, Some(span), LangItem::PanicCannotUnwind);
 
         // Codegen the actual panic invoke/call.
         let merging_succ = helper.do_call(self, bx, fn_abi, llfn, &[], None, None, &[], false);
@@ -698,19 +698,18 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     })
                 });
                 let msg = bx.const_str(&msg_str);
-                let location = self.get_caller_location(bx, source_info).immediate();
 
                 // Obtain the panic entry point.
                 let (fn_abi, llfn) =
-                    common::build_langcall(bx, Some(source_info.span), LangItem::Panic);
+                    common::build_langcall(bx, Some(source_info.span), LangItem::PanicNounwind);
 
                 // Codegen the actual panic invoke/call.
                 helper.do_call(
                     self,
                     bx,
                     fn_abi,
                     llfn,
-                    &[msg.0, msg.1, location],
+                    &[msg.0, msg.1],
                     target.as_ref().map(|bb| (ReturnDest::Nothing, *bb)),
                     cleanup,
                     &[],
@@ -1665,7 +1664,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             let llpersonality = self.cx.eh_personality();
             bx.cleanup_landing_pad(llpersonality);
 
-            let (fn_abi, fn_ptr) = common::build_langcall(&bx, None, LangItem::PanicNoUnwind);
+            let (fn_abi, fn_ptr) = common::build_langcall(&bx, None, LangItem::PanicCannotUnwind);
             let fn_ty = bx.fn_decl_backend_type(&fn_abi);
 
             let llret = bx.call(fn_ty, Some(&fn_abi), fn_ptr, &[], None);

compiler/rustc_hir/src/lang_items.rs

@@ -146,7 +146,7 @@ pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
 }
 
 language_item_table! {
-//  Variant name,            Name,                     Method name,                Target                  Generic requirements;
+//  Variant name,            Name,                     Getter method name,         Target                  Generic requirements;
     Sized,                   sym::sized,               sized_trait,                Target::Trait,          GenericRequirement::Exact(0);
     Unsize,                  sym::unsize,              unsize_trait,               Target::Trait,          GenericRequirement::Minimum(1);
     /// Trait injected by `#[derive(PartialEq)]`, (i.e. "Partial EQ").
@@ -232,14 +232,15 @@ language_item_table! {
     // is required to define it somewhere. Additionally, there are restrictions on crates that use
     // a weak lang item, but do not have it defined.
     Panic,                   sym::panic,               panic_fn,                   Target::Fn,             GenericRequirement::Exact(0);
+    PanicNounwind,           sym::panic_nounwind,      panic_nounwind,             Target::Fn,             GenericRequirement::Exact(0);
     PanicFmt,                sym::panic_fmt,           panic_fmt,                  Target::Fn,             GenericRequirement::None;
     PanicDisplay,            sym::panic_display,       panic_display,              Target::Fn,             GenericRequirement::None;
     ConstPanicFmt,           sym::const_panic_fmt,     const_panic_fmt,            Target::Fn,             GenericRequirement::None;
     PanicBoundsCheck,        sym::panic_bounds_check,  panic_bounds_check_fn,      Target::Fn,             GenericRequirement::Exact(0);
     PanicInfo,               sym::panic_info,          panic_info,                 Target::Struct,         GenericRequirement::None;
     PanicLocation,           sym::panic_location,      panic_location,             Target::Struct,         GenericRequirement::None;
     PanicImpl,               sym::panic_impl,          panic_impl,                 Target::Fn,             GenericRequirement::None;
-    PanicNoUnwind,           sym::panic_no_unwind,     panic_no_unwind,            Target::Fn,             GenericRequirement::Exact(0);
+    PanicCannotUnwind,       sym::panic_cannot_unwind, panic_cannot_unwind,        Target::Fn,             GenericRequirement::Exact(0);
     /// libstd panic entry point. Necessary for const eval to be able to catch it
     BeginPanic,              sym::begin_panic,         begin_panic_fn,             Target::Fn,             GenericRequirement::None;
 

compiler/rustc_monomorphize/src/collector.rs

@@ -843,7 +843,7 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
             mir::TerminatorKind::Abort { .. } => {
                 let instance = Instance::mono(
                     tcx,
-                    tcx.require_lang_item(LangItem::PanicNoUnwind, Some(source)),
+                    tcx.require_lang_item(LangItem::PanicCannotUnwind, Some(source)),
                 );
                 if should_codegen_locally(tcx, &instance) {
                     self.output.push(create_fn_mono_item(tcx, instance, source));

compiler/rustc_span/src/symbol.rs

@@ -1041,14 +1041,15 @@ symbols! {
         panic_2021,
         panic_abort,
         panic_bounds_check,
+        panic_cannot_unwind,
         panic_display,
         panic_fmt,
         panic_handler,
         panic_impl,
         panic_implementation,
         panic_info,
         panic_location,
-        panic_no_unwind,
+        panic_nounwind,
         panic_runtime,
         panic_str,
         panic_unwind,

library/core/src/intrinsics.rs

@@ -2281,7 +2281,7 @@ macro_rules! assert_unsafe_precondition {
             fn runtime$(<$($tt)*>)?($($i:$ty),*) {
                 if !$e {
                     // don't unwind to reduce impact on code size
-                    ::core::panicking::panic_str_nounwind(
+                    ::core::panicking::panic_nounwind(
                         concat!("unsafe precondition(s) violated: ", $name)
                     );
                 }

library/core/src/panicking.rs

@@ -64,12 +64,13 @@ pub const fn panic_fmt(fmt: fmt::Arguments<'_>) -> ! {
     unsafe { panic_impl(&pi) }
 }
 
-/// Like panic_fmt, but without unwinding and track_caller to reduce the impact on codesize.
-/// Also just works on `str`, as a `fmt::Arguments` needs more space to be passed.
+/// Like `panic`, but without unwinding and track_caller to reduce the impact on codesize.
+/// (No `fmt` variant as a `fmt::Arguments` needs more space to be passed.)
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
 #[cfg_attr(feature = "panic_immediate_abort", inline)]
+#[cfg_attr(not(bootstrap), lang = "panic_nounwind")] // needed by codegen for non-unwinding panics
 #[rustc_nounwind]
-pub fn panic_str_nounwind(msg: &'static str) -> ! {
+pub fn panic_nounwind(msg: &'static str) -> ! {
     if cfg!(feature = "panic_immediate_abort") {
         super::intrinsics::abort()
     }
@@ -153,10 +154,11 @@ fn panic_bounds_check(index: usize, len: usize) -> ! {
 /// any extra arguments (including those synthesized by track_caller).
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
 #[cfg_attr(feature = "panic_immediate_abort", inline)]
-#[lang = "panic_no_unwind"] // needed by codegen for panic in nounwind function
+#[cfg_attr(bootstrap, lang = "panic_no_unwind")] // needed by codegen for panic in nounwind function
+#[cfg_attr(not(bootstrap), lang = "panic_cannot_unwind")] // needed by codegen for panic in nounwind function
 #[rustc_nounwind]
-fn panic_no_unwind() -> ! {
-    panic_str_nounwind("panic in a function that cannot unwind")
+fn panic_cannot_unwind() -> ! {
+    panic_nounwind("panic in a function that cannot unwind")
 }
 
 /// This function is used instead of panic_fmt in const eval.

src/test/codegen/unwind-abis/c-unwind-abi-panic-abort.rs

@@ -10,7 +10,7 @@
 #[no_mangle]
 pub unsafe extern "C-unwind" fn rust_item_that_can_unwind() {
     // Handle both legacy and v0 symbol mangling.
-    // CHECK: call void @{{.*core9panicking15panic_no_unwind}}
+    // CHECK: call void @{{.*core9panicking19panic_cannot_unwind}}
     may_unwind();
 }
 

src/test/codegen/unwind-and-panic-abort.rs

@@ -10,7 +10,7 @@ extern "C-unwind" {
 // CHECK: Function Attrs:{{.*}}nounwind
 // CHECK-NEXT: define{{.*}}void @foo
 // Handle both legacy and v0 symbol mangling.
-// CHECK: call void @{{.*core9panicking15panic_no_unwind}}
+// CHECK: call void @{{.*core9panicking19panic_cannot_unwind}}
 #[no_mangle]
 pub unsafe extern "C" fn foo() {
     bar();

src/test/ui/intrinsics/panic-uninitialized-zeroed.rs

@@ -1,7 +1,5 @@
 // run-pass
-// needs-unwind
-// revisions: mir thir strict
-// [thir]compile-flags: -Zthir-unsafeck
+// revisions: default strict
 // [strict]compile-flags: -Zstrict-init-checks
 // ignore-tidy-linelength
 
@@ -12,7 +10,6 @@
 
 use std::{
     mem::{self, MaybeUninit, ManuallyDrop},
-    panic,
     ptr::NonNull,
     num,
 };
@@ -70,21 +67,42 @@ enum ZeroIsValid {
 }
 
 #[track_caller]
-fn test_panic_msg<T>(op: impl (FnOnce() -> T) + panic::UnwindSafe, msg: &str) {
-    let err = panic::catch_unwind(op).err();
-    assert_eq!(
-        err.as_ref().and_then(|a| a.downcast_ref::<&str>()),
-        Some(&msg)
-    );
+fn test_panic_msg<T, F: (FnOnce() -> T) + 'static>(op: F, msg: &str) {
+    use std::{panic, env, process};
+
+    // The tricky part is that we can't just run `op`, as that would *abort* the process.
+    // So instead, we reinvoke this process with the caller location as argument.
+    // For the purpose of this test, the line number is unique enough.
+    // If we are running in such a re-invocation, we skip all the tests *except* for the one with that type name.
+    let our_loc = panic::Location::caller().line().to_string();
+    let mut args = env::args();
+    let this = args.next().unwrap();
+    if let Some(loc) = args.next() {
+        if loc == our_loc {
+            op();
+            panic!("we did not abort");
+        } else {
+            // Nothing, we are running another test.
+        }
+    } else {
+        // Invoke new process for actual test, and check result.
+        let mut cmd = process::Command::new(this);
+        cmd.arg(our_loc);
+        let res = cmd.output().unwrap();
+        assert!(!res.status.success(), "test did not fail");
+        let stderr = String::from_utf8_lossy(&res.stderr);
+        assert!(stderr.contains(msg), "test did not contain expected output: looking for {:?}, output:\n{}", msg, stderr);
+    }
 }
 
 #[track_caller]
-fn test_panic_msg_only_if_strict<T>(op: impl (FnOnce() -> T) + panic::UnwindSafe, msg: &str) {
-    let err = panic::catch_unwind(op).err();
-    assert_eq!(
-        err.as_ref().and_then(|a| a.downcast_ref::<&str>()),
-        if cfg!(strict) { Some(&msg) } else { None },
-    );
+fn test_panic_msg_only_if_strict<T>(op: impl (FnOnce() -> T) + 'static, msg: &str) {
+    if !cfg!(strict) {
+        // Just run it.
+        op();
+    } else {
+        test_panic_msg(op, msg);
+    }
 }
 
 fn main() {