Rollup merge of rust-lang#115280 - RalfJung:panic-cleanup-triple-backtrace, r=Amanieu

avoid triple-backtrace due to panic-during-cleanup

Supersedes rust-lang#115020
Cc rust-lang#114954
r? ``@Amanieu``

Author: matthiaskrgr

alloc/src/alloc.rs

@@ -408,9 +408,10 @@ pub mod __alloc_error_handler {
         if unsafe { __rust_alloc_error_handler_should_panic != 0 } {
             panic!("memory allocation of {size} bytes failed")
         } else {
-            core::panicking::panic_nounwind_fmt(format_args!(
-                "memory allocation of {size} bytes failed"
-            ))
+            core::panicking::panic_nounwind_fmt(
+                format_args!("memory allocation of {size} bytes failed"),
+                /* force_no_backtrace */ false,
+            )
         }
     }
 }

core/src/panic/panic_info.rs

@@ -28,6 +28,7 @@ pub struct PanicInfo<'a> {
     message: Option<&'a fmt::Arguments<'a>>,
     location: &'a Location<'a>,
     can_unwind: bool,
+    force_no_backtrace: bool,
 }
 
 impl<'a> PanicInfo<'a> {
@@ -42,9 +43,10 @@ impl<'a> PanicInfo<'a> {
         message: Option<&'a fmt::Arguments<'a>>,
         location: &'a Location<'a>,
         can_unwind: bool,
+        force_no_backtrace: bool,
     ) -> Self {
         struct NoPayload;
-        PanicInfo { location, message, payload: &NoPayload, can_unwind }
+        PanicInfo { location, message, payload: &NoPayload, can_unwind, force_no_backtrace }
     }
 
     #[unstable(
@@ -141,6 +143,17 @@ impl<'a> PanicInfo<'a> {
     pub fn can_unwind(&self) -> bool {
         self.can_unwind
     }
+
+    #[unstable(
+        feature = "panic_internals",
+        reason = "internal details of the implementation of the `panic!` and related macros",
+        issue = "none"
+    )]
+    #[doc(hidden)]
+    #[inline]
+    pub fn force_no_backtrace(&self) -> bool {
+        self.force_no_backtrace
+    }
 }
 
 #[stable(feature = "panic_hook_display", since = "1.26.0")]

core/src/panicking.rs

@@ -61,7 +61,12 @@ pub const fn panic_fmt(fmt: fmt::Arguments<'_>) -> ! {
         fn panic_impl(pi: &PanicInfo<'_>) -> !;
     }
 
-    let pi = PanicInfo::internal_constructor(Some(&fmt), Location::caller(), true);
+    let pi = PanicInfo::internal_constructor(
+        Some(&fmt),
+        Location::caller(),
+        /* can_unwind */ true,
+        /* force_no_backtrace */ false,
+    );
 
     // SAFETY: `panic_impl` is defined in safe Rust code and thus is safe to call.
     unsafe { panic_impl(&pi) }
@@ -77,7 +82,7 @@ pub const fn panic_fmt(fmt: fmt::Arguments<'_>) -> ! {
 // and unwinds anyway, we will hit the "unwinding out of nounwind function" guard,
 // which causes a "panic in a function that cannot unwind".
 #[rustc_nounwind]
-pub fn panic_nounwind_fmt(fmt: fmt::Arguments<'_>) -> ! {
+pub fn panic_nounwind_fmt(fmt: fmt::Arguments<'_>, force_no_backtrace: bool) -> ! {
     if cfg!(feature = "panic_immediate_abort") {
         super::intrinsics::abort()
     }
@@ -90,7 +95,12 @@ pub fn panic_nounwind_fmt(fmt: fmt::Arguments<'_>) -> ! {
     }
 
     // PanicInfo with the `can_unwind` flag set to false forces an abort.
-    let pi = PanicInfo::internal_constructor(Some(&fmt), Location::caller(), false);
+    let pi = PanicInfo::internal_constructor(
+        Some(&fmt),
+        Location::caller(),
+        /* can_unwind */ false,
+        force_no_backtrace,
+    );
 
     // SAFETY: `panic_impl` is defined in safe Rust code and thus is safe to call.
     unsafe { panic_impl(&pi) }
@@ -123,7 +133,15 @@ pub const fn panic(expr: &'static str) -> ! {
 #[lang = "panic_nounwind"] // needed by codegen for non-unwinding panics
 #[rustc_nounwind]
 pub fn panic_nounwind(expr: &'static str) -> ! {
-    panic_nounwind_fmt(fmt::Arguments::new_const(&[expr]));
+    panic_nounwind_fmt(fmt::Arguments::new_const(&[expr]), /* force_no_backtrace */ false);
+}
+
+/// Like `panic_nounwind`, but also inhibits showing a backtrace.
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold)]
+#[cfg_attr(feature = "panic_immediate_abort", inline)]
+#[rustc_nounwind]
+pub fn panic_nounwind_nobacktrace(expr: &'static str) -> ! {
+    panic_nounwind_fmt(fmt::Arguments::new_const(&[expr]), /* force_no_backtrace */ true);
 }
 
 #[inline]
@@ -172,9 +190,12 @@ fn panic_misaligned_pointer_dereference(required: usize, found: usize) -> ! {
         super::intrinsics::abort()
     }
 
-    panic_nounwind_fmt(format_args!(
-        "misaligned pointer dereference: address must be a multiple of {required:#x} but is {found:#x}"
-    ))
+    panic_nounwind_fmt(
+        format_args!(
+            "misaligned pointer dereference: address must be a multiple of {required:#x} but is {found:#x}"
+        ),
+        /* force_no_backtrace */ false,
+    )
 }
 
 /// Panic because we cannot unwind out of a function.
@@ -205,7 +226,7 @@ fn panic_cannot_unwind() -> ! {
 #[rustc_nounwind]
 fn panic_in_cleanup() -> ! {
     // Keep the text in sync with `UnwindTerminateReason::as_str` in `rustc_middle`.
-    panic_nounwind("panic in a destructor during cleanup")
+    panic_nounwind_nobacktrace("panic in a destructor during cleanup")
 }
 
 /// This function is used instead of panic_fmt in const eval.

std/src/panicking.rs

@@ -246,7 +246,9 @@ fn default_hook(info: &PanicInfo<'_>) {
 pub fn panic_hook_with_disk_dump(info: &PanicInfo<'_>, path: Option<&crate::path::Path>) {
     // If this is a double panic, make sure that we print a backtrace
     // for this panic. Otherwise only print it if logging is enabled.
-    let backtrace = if panic_count::get_count() >= 2 {
+    let backtrace = if info.force_no_backtrace() {
+        None
+    } else if panic_count::get_count() >= 2 {
         BacktraceStyle::full()
     } else {
         crate::panic::get_backtrace_style()
@@ -294,7 +296,7 @@ pub fn panic_hook_with_disk_dump(info: &PanicInfo<'_>, path: Option<&crate::path
                     }
                 }
             }
-            // If backtraces aren't supported, do nothing.
+            // If backtraces aren't supported or are forced-off, do nothing.
             None => {}
         }
     };
@@ -615,14 +617,23 @@ pub fn begin_panic_handler(info: &PanicInfo<'_>) -> ! {
     let loc = info.location().unwrap(); // The current implementation always returns Some
     let msg = info.message().unwrap(); // The current implementation always returns Some
     crate::sys_common::backtrace::__rust_end_short_backtrace(move || {
+        // FIXME: can we just pass `info` along rather than taking it apart here, only to have
+        // `rust_panic_with_hook` construct a new `PanicInfo`?
         if let Some(msg) = msg.as_str() {
-            rust_panic_with_hook(&mut StrPanicPayload(msg), info.message(), loc, info.can_unwind());
+            rust_panic_with_hook(
+                &mut StrPanicPayload(msg),
+                info.message(),
+                loc,
+                info.can_unwind(),
+                info.force_no_backtrace(),
+            );
         } else {
             rust_panic_with_hook(
                 &mut PanicPayload::new(msg),
                 info.message(),
                 loc,
                 info.can_unwind(),
+                info.force_no_backtrace(),
             );
         }
     })
@@ -647,7 +658,13 @@ pub const fn begin_panic<M: Any + Send>(msg: M) -> ! {
 
     let loc = Location::caller();
     return crate::sys_common::backtrace::__rust_end_short_backtrace(move || {
-        rust_panic_with_hook(&mut PanicPayload::new(msg), None, loc, true)
+        rust_panic_with_hook(
+            &mut PanicPayload::new(msg),
+            None,
+            loc,
+            /* can_unwind */ true,
+            /* force_no_backtrace */ false,
+        )
     });
 
     struct PanicPayload<A> {
@@ -693,6 +710,7 @@ fn rust_panic_with_hook(
     message: Option<&fmt::Arguments<'_>>,
     location: &Location<'_>,
     can_unwind: bool,
+    force_no_backtrace: bool,
 ) -> ! {
     let must_abort = panic_count::increase(true);
 
@@ -707,14 +725,20 @@ fn rust_panic_with_hook(
             panic_count::MustAbort::AlwaysAbort => {
                 // Unfortunately, this does not print a backtrace, because creating
                 // a `Backtrace` will allocate, which we must to avoid here.
-                let panicinfo = PanicInfo::internal_constructor(message, location, can_unwind);
+                let panicinfo = PanicInfo::internal_constructor(
+                    message,
+                    location,
+                    can_unwind,
+                    force_no_backtrace,
+                );
                 rtprintpanic!("{panicinfo}\npanicked after panic::always_abort(), aborting.\n");
             }
         }
         crate::sys::abort_internal();
     }
 
-    let mut info = PanicInfo::internal_constructor(message, location, can_unwind);
+    let mut info =
+        PanicInfo::internal_constructor(message, location, can_unwind, force_no_backtrace);
     let hook = HOOK.read().unwrap_or_else(PoisonError::into_inner);
     match *hook {
         // Some platforms (like wasm) know that printing to stderr won't ever actually