Auto merge of #141133 - matthiaskrgr:rollup-u8ndxyz, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #135808 (Implement Display for ``rustc_target::callconv::Conv``)
 - #137432 (Add as_ascii_unchecked() methods to char, u8, and str)
 - #139103 (deduplicate abort implementations)
 - #140917 (checktools.sh: fix bashism)
 - #141035 (turn lld warning on old gccs into info log)
 - #141118 (Enable rust-analyzer to go from query definition to the corresponding provider field)
 - #141121 (Only select true errors in `impossible_predicates`)
 - #141125 (check coroutines with `TypingMode::Borrowck` to avoid cyclic reasoning)
 - #141131 (Make some `match`es slightly more ergonomic in `librustdoc`)

r? `@ghost`
`@rustbot` modify labels: rollup

14 files changed, 105 insertions, 117 deletions

diff --git a/library/Cargo.lock b/library/Cargo.lock
index 97ca3cb06b2..02018057ed5 100644
--- a/library/Cargo.lock
+++ b/library/Cargo.lock
@@ -196,7 +196,6 @@ name = "panic_abort"
 version = "0.0.0"
 dependencies = [
  "alloc",
- "cfg-if",
  "compiler_builtins",
  "core",
  "libc",
diff --git a/library/core/src/char/methods.rs b/library/core/src/char/methods.rs
index 042925a352f..af2edf141b2 100644
--- a/library/core/src/char/methods.rs
+++ b/library/core/src/char/methods.rs
@@ -4,6 +4,7 @@ use super::*;
 use crate::panic::const_panic;
 use crate::slice;
 use crate::str::from_utf8_unchecked_mut;
+use crate::ub_checks::assert_unsafe_precondition;
 use crate::unicode::printable::is_printable;
 use crate::unicode::{self, conversions};
 
@@ -1202,6 +1203,26 @@ impl char {
         }
     }
 
+    /// Converts this char into an [ASCII character](`ascii::Char`), without
+    /// checking whether it is valid.
+    ///
+    /// # Safety
+    ///
+    /// This char must be within the ASCII range, or else this is UB.
+    #[must_use]
+    #[unstable(feature = "ascii_char", issue = "110998")]
+    #[inline]
+    pub const unsafe fn as_ascii_unchecked(&self) -> ascii::Char {
+        assert_unsafe_precondition!(
+            check_library_ub,
+            "as_ascii_unchecked requires that the char is valid ASCII",
+            (it: &char = self) => it.is_ascii()
+        );
+
+        // SAFETY: the caller promised that this char is ASCII.
+        unsafe { ascii::Char::from_u8_unchecked(*self as u8) }
+    }
+
     /// Makes a copy of the value in its ASCII upper case equivalent.
     ///
     /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs
index ecc1c7bf902..a82b2aa61ce 100644
--- a/library/core/src/num/mod.rs
+++ b/library/core/src/num/mod.rs
@@ -492,6 +492,26 @@ impl u8 {
         ascii::Char::from_u8(*self)
     }
 
+    /// Converts this byte to an [ASCII character](ascii::Char), without
+    /// checking whether or not it's valid.
+    ///
+    /// # Safety
+    ///
+    /// This byte must be valid ASCII, or else this is UB.
+    #[must_use]
+    #[unstable(feature = "ascii_char", issue = "110998")]
+    #[inline]
+    pub const unsafe fn as_ascii_unchecked(&self) -> ascii::Char {
+        assert_unsafe_precondition!(
+            check_library_ub,
+            "as_ascii_unchecked requires that the byte is valid ASCII",
+            (it: &u8 = self) => it.is_ascii()
+        );
+
+        // SAFETY: the caller promised that this byte is ASCII.
+        unsafe { ascii::Char::from_u8_unchecked(*self) }
+    }
+
     /// Makes a copy of the value in its ASCII upper case equivalent.
     ///
     /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs
index 9e7e949b722..e505e228095 100644
--- a/library/core/src/str/mod.rs
+++ b/library/core/src/str/mod.rs
@@ -17,6 +17,7 @@ use self::pattern::{DoubleEndedSearcher, Pattern, ReverseSearcher, Searcher};
 use crate::char::{self, EscapeDebugExtArgs};
 use crate::ops::Range;
 use crate::slice::{self, SliceIndex};
+use crate::ub_checks::assert_unsafe_precondition;
 use crate::{ascii, mem};
 
 pub mod pattern;
@@ -2634,6 +2635,27 @@ impl str {
         self.as_bytes().as_ascii()
     }
 
+    /// Converts this string slice into a slice of [ASCII characters](ascii::Char),
+    /// without checking whether they are valid.
+    ///
+    /// # Safety
+    ///
+    /// Every character in this string must be ASCII, or else this is UB.
+    #[unstable(feature = "ascii_char", issue = "110998")]
+    #[must_use]
+    #[inline]
+    pub const unsafe fn as_ascii_unchecked(&self) -> &[ascii::Char] {
+        assert_unsafe_precondition!(
+            check_library_ub,
+            "as_ascii_unchecked requires that the string is valid ASCII",
+            (it: &str = self) => it.is_ascii()
+        );
+
+        // SAFETY: the caller promised that every byte of this string slice
+        // is ASCII.
+        unsafe { self.as_bytes().as_ascii_unchecked() }
+    }
+
     /// Checks that two strings are an ASCII case-insensitive match.
     ///
     /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`,
diff --git a/library/panic_abort/Cargo.toml b/library/panic_abort/Cargo.toml
index 6f43ac4809a..d7d169671f0 100644
--- a/library/panic_abort/Cargo.toml
+++ b/library/panic_abort/Cargo.toml
@@ -12,10 +12,11 @@ bench = false
 doc = false
 
 [dependencies]
-alloc = { path = "../alloc" }
-cfg-if = { version = "1.0", features = ['rustc-dep-of-std'] }
 core = { path = "../core" }
 compiler_builtins = "0.1.0"
 
-[target.'cfg(not(all(windows, target_env = "msvc")))'.dependencies]
+[target.'cfg(target_os = "android")'.dependencies]
 libc = { version = "0.2", default-features = false }
+
+[target.'cfg(any(target_os = "android", target_os = "zkvm"))'.dependencies]
+alloc = { path = "../alloc" }
diff --git a/library/panic_abort/src/lib.rs b/library/panic_abort/src/lib.rs
index b2ad0f4ac3d..d1706b65252 100644
--- a/library/panic_abort/src/lib.rs
+++ b/library/panic_abort/src/lib.rs
@@ -7,15 +7,11 @@
 #![unstable(feature = "panic_abort", issue = "32837")]
 #![doc(issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
 #![panic_runtime]
-#![allow(unused_features)]
-#![feature(asm_experimental_arch)]
-#![feature(core_intrinsics)]
 #![feature(panic_runtime)]
 #![feature(std_internals)]
 #![feature(staged_api)]
 #![feature(rustc_attrs)]
 #![allow(internal_features)]
-#![deny(unsafe_op_in_unsafe_fn)]
 
 #[cfg(target_os = "android")]
 mod android;
@@ -45,75 +41,13 @@ pub unsafe fn __rust_start_panic(_payload: &mut dyn PanicPayload) -> u32 {
         zkvm::zkvm_set_abort_message(_payload);
     }
 
-    unsafe {
-        abort();
+    unsafe extern "Rust" {
+        // This is defined in std::rt.
+        #[rustc_std_internal_symbol]
+        safe fn __rust_abort() -> !;
     }
 
-    cfg_if::cfg_if! {
-        if #[cfg(any(unix, target_os = "solid_asp3"))] {
-            unsafe fn abort() -> ! {
-                unsafe { libc::abort(); }
-            }
-        } else if #[cfg(any(target_os = "hermit",
-                            all(target_vendor = "fortanix", target_env = "sgx"),
-                            target_os = "xous",
-                            target_os = "uefi",
-        ))] {
-            unsafe fn abort() -> ! {
-                // call std::sys::abort_internal
-                unsafe extern "C" {
-                    pub fn __rust_abort() -> !;
-                }
-                unsafe { __rust_abort(); }
-            }
-        } else if #[cfg(all(windows, not(miri)))] {
-            // On Windows, use the processor-specific __fastfail mechanism. In Windows 8
-            // and later, this will terminate the process immediately without running any
-            // in-process exception handlers. In earlier versions of Windows, this
-            // sequence of instructions will be treated as an access violation,
-            // terminating the process but without necessarily bypassing all exception
-            // handlers.
-            //
-            // https://docs.microsoft.com/en-us/cpp/intrinsics/fastfail
-            //
-            // Note: this is the same implementation as in std's `abort_internal`
-            unsafe fn abort() -> ! {
-                #[allow(unused)]
-                const FAST_FAIL_FATAL_APP_EXIT: usize = 7;
-                cfg_if::cfg_if! {
-                    if #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
-                        unsafe {
-                            core::arch::asm!("int $$0x29", in("ecx") FAST_FAIL_FATAL_APP_EXIT, options(noreturn, nostack));
-                        }
-                    } else if #[cfg(all(target_arch = "arm", target_feature = "thumb-mode"))] {
-                        unsafe {
-                            core::arch::asm!(".inst 0xDEFB", in("r0") FAST_FAIL_FATAL_APP_EXIT, options(noreturn, nostack));
-                        }
-                    } else if #[cfg(any(target_arch = "aarch64", target_arch = "arm64ec"))] {
-                        unsafe {
-                            core::arch::asm!("brk 0xF003", in("x0") FAST_FAIL_FATAL_APP_EXIT, options(noreturn, nostack));
-                        }
-                    } else {
-                        core::intrinsics::abort();
-                    }
-                }
-            }
-        } else if #[cfg(target_os = "teeos")] {
-            mod teeos {
-                unsafe extern "C" {
-                    pub fn TEE_Panic(code: u32) -> !;
-                }
-            }
-
-            unsafe fn abort() -> ! {
-                unsafe { teeos::TEE_Panic(1); }
-            }
-        } else {
-            unsafe fn abort() -> ! {
-                core::intrinsics::abort();
-            }
-        }
-    }
+    __rust_abort()
 }
 
 // This... is a bit of an oddity. The tl;dr; is that this is required to link
diff --git a/library/panic_unwind/src/hermit.rs b/library/panic_unwind/src/hermit.rs
index 8f4562d07fc..b36d1a019fd 100644
--- a/library/panic_unwind/src/hermit.rs
+++ b/library/panic_unwind/src/hermit.rs
@@ -5,20 +5,16 @@
 use alloc::boxed::Box;
 use core::any::Any;
 
+unsafe extern "Rust" {
+    // This is defined in std::rt
+    #[rustc_std_internal_symbol]
+    safe fn __rust_abort() -> !;
+}
+
 pub(crate) unsafe fn cleanup(_ptr: *mut u8) -> Box<dyn Any + Send> {
-    unsafe extern "C" {
-        fn __rust_abort() -> !;
-    }
-    unsafe {
-        __rust_abort();
-    }
+    __rust_abort()
 }
 
 pub(crate) unsafe fn panic(_data: Box<dyn Any + Send>) -> u32 {
-    unsafe extern "C" {
-        fn __rust_abort() -> !;
-    }
-    unsafe {
-        __rust_abort();
-    }
+    __rust_abort()
 }
diff --git a/library/std/src/rt.rs b/library/std/src/rt.rs
index 9737b2f5bfe..b3f3b301e3d 100644
--- a/library/std/src/rt.rs
+++ b/library/std/src/rt.rs
@@ -26,6 +26,13 @@ use crate::sync::Once;
 use crate::thread::{self, main_thread};
 use crate::{mem, panic, sys};
 
+// This function is needed by the panic runtime.
+#[cfg(not(test))]
+#[rustc_std_internal_symbol]
+fn __rust_abort() {
+    crate::process::abort();
+}
+
 // Prints to the "panic output", depending on the platform this may be:
 // - the standard error output
 // - some dedicated platform specific output
@@ -47,7 +54,7 @@ macro_rules! rtabort {
     ($($t:tt)*) => {
         {
             rtprintpanic!("fatal runtime error: {}, aborting\n", format_args!($($t)*));
-            crate::sys::abort_internal();
+            crate::process::abort();
         }
     }
 }
diff --git a/library/std/src/sys/pal/hermit/mod.rs b/library/std/src/sys/pal/hermit/mod.rs
index ea636938d70..fb8d69b7375 100644
--- a/library/std/src/sys/pal/hermit/mod.rs
+++ b/library/std/src/sys/pal/hermit/mod.rs
@@ -43,15 +43,6 @@ pub fn abort_internal() -> ! {
     unsafe { hermit_abi::abort() }
 }
 
-// This function is needed by the panic runtime. The symbol is named in
-// pre-link args for the target specification, so keep that in sync.
-#[cfg(not(test))]
-#[unsafe(no_mangle)]
-// NB. used by both libunwind and libpanic_abort
-pub extern "C" fn __rust_abort() {
-    abort_internal();
-}
-
 // SAFETY: must be called only once during runtime initialization.
 // NOTE: this is not guaranteed to run, for example when Rust code is called externally.
 pub unsafe fn init(argc: isize, argv: *const *const u8, _sigpipe: u8) {
diff --git a/library/std/src/sys/pal/sgx/mod.rs b/library/std/src/sys/pal/sgx/mod.rs
index 3932f64c0ef..6e43a79ddec 100644
--- a/library/std/src/sys/pal/sgx/mod.rs
+++ b/library/std/src/sys/pal/sgx/mod.rs
@@ -112,11 +112,14 @@ pub fn abort_internal() -> ! {
     abi::usercalls::exit(true)
 }
 
-// This function is needed by the panic runtime. The symbol is named in
+// This function is needed by libunwind. The symbol is named in
 // pre-link args for the target specification, so keep that in sync.
+// Note: contrary to the `__rust_abort` in `crate::rt`, this uses `no_mangle`
+//       because it is actually used from C code. Because symbols annotated with
+//       #[rustc_std_internal_symbol] get mangled, this will not lead to linker
+//       conflicts.
 #[cfg(not(test))]
 #[unsafe(no_mangle)]
-// NB. used by both libunwind and libpanic_abort
 pub extern "C" fn __rust_abort() {
     abort_internal();
 }
diff --git a/library/std/src/sys/pal/uefi/mod.rs b/library/std/src/sys/pal/uefi/mod.rs
index 78fcfcb3b77..8911a2ee519 100644
--- a/library/std/src/sys/pal/uefi/mod.rs
+++ b/library/std/src/sys/pal/uefi/mod.rs
@@ -161,14 +161,6 @@ pub fn abort_internal() -> ! {
     core::intrinsics::abort();
 }
 
-// This function is needed by the panic runtime. The symbol is named in
-// pre-link args for the target specification, so keep that in sync.
-#[cfg(not(test))]
-#[unsafe(no_mangle)]
-pub extern "C" fn __rust_abort() {
-    abort_internal();
-}
-
 /// Disable access to BootServices if `EVT_SIGNAL_EXIT_BOOT_SERVICES` is signaled
 extern "efiapi" fn exit_boot_service_handler(_e: r_efi::efi::Event, _ctx: *mut crate::ffi::c_void) {
     uefi::env::disable_boot_services();
diff --git a/library/std/src/sys/pal/windows/mod.rs b/library/std/src/sys/pal/windows/mod.rs
index 4f18c4009ab..8f54e2376eb 100644
--- a/library/std/src/sys/pal/windows/mod.rs
+++ b/library/std/src/sys/pal/windows/mod.rs
@@ -328,8 +328,12 @@ pub fn dur2timeout(dur: Duration) -> u32 {
 
 /// Use `__fastfail` to abort the process
 ///
-/// This is the same implementation as in libpanic_abort's `__rust_start_panic`. See
-/// that function for more information on `__fastfail`
+/// In Windows 8 and later, this will terminate the process immediately without
+/// running any in-process exception handlers. In earlier versions of Windows,
+/// this sequence of instructions will be treated as an access violation, which
+/// will still terminate the process but might run some exception handlers.
+///
+/// https://docs.microsoft.com/en-us/cpp/intrinsics/fastfail
 #[cfg(not(miri))] // inline assembly does not work in Miri
 pub fn abort_internal() -> ! {
     unsafe {
diff --git a/library/std/src/sys/pal/xous/mod.rs b/library/std/src/sys/pal/xous/mod.rs
index 383d031ed43..042c4ff862f 100644
--- a/library/std/src/sys/pal/xous/mod.rs
+++ b/library/std/src/sys/pal/xous/mod.rs
@@ -1,5 +1,7 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
+use crate::os::xous::ffi::exit;
+
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
@@ -9,3 +11,7 @@ pub mod time;
 #[path = "../unsupported/common.rs"]
 mod common;
 pub use common::*;
+
+pub fn abort_internal() -> ! {
+    exit(101);
+}
diff --git a/library/std/src/sys/pal/xous/os.rs b/library/std/src/sys/pal/xous/os.rs
index 2230dabe096..d612a27d2bd 100644
--- a/library/std/src/sys/pal/xous/os.rs
+++ b/library/std/src/sys/pal/xous/os.rs
@@ -62,14 +62,6 @@ mod c_compat {
         }
         exit(unsafe { main() });
     }
-
-    // This function is needed by the panic runtime. The symbol is named in
-    // pre-link args for the target specification, so keep that in sync.
-    #[unsafe(no_mangle)]
-    // NB. used by both libunwind and libpanic_abort
-    pub extern "C" fn __rust_abort() -> ! {
-        exit(101);
-    }
 }
 
 pub fn errno() -> i32 {