Rollup of 7 pull requests

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -339,24 +339,32 @@ pub fn llvm_global_features(sess: &Session) -> Vec<String> {
         Some(_) | None => {}
     };
 
+    let filter = |s: &str| {
+        if s.is_empty() {
+            return None;
+        }
+        let feature = if s.starts_with("+") || s.starts_with("-") {
+            &s[1..]
+        } else {
+            return Some(s.to_string());
+        };
+        // Rustc-specific feature requests like `+crt-static` or `-crt-static`
+        // are not passed down to LLVM.
+        if RUSTC_SPECIFIC_FEATURES.contains(&feature) {
+            return None;
+        }
+        // ... otherwise though we run through `to_llvm_feature` feature when
+        // passing requests down to LLVM. This means that all in-language
+        // features also work on the command line instead of having two
+        // different names when the LLVM name and the Rust name differ.
+        Some(format!("{}{}", &s[..1], to_llvm_feature(sess, feature)))
+    };
+
     // Features implied by an implicit or explicit `--target`.
-    features.extend(
-        sess.target
-            .features
-            .split(',')
-            .filter(|f| !f.is_empty() && !RUSTC_SPECIFIC_FEATURES.iter().any(|s| f.contains(s)))
-            .map(String::from),
-    );
+    features.extend(sess.target.features.split(',').filter_map(&filter));
 
     // -Ctarget-features
-    features.extend(
-        sess.opts
-            .cg
-            .target_feature
-            .split(',')
-            .filter(|f| !f.is_empty() && !RUSTC_SPECIFIC_FEATURES.iter().any(|s| f.contains(s)))
-            .map(String::from),
-    );
+    features.extend(sess.opts.cg.target_feature.split(',').filter_map(&filter));
 
     features
 }

compiler/rustc_codegen_ssa/src/back/linker.rs

@@ -340,6 +340,14 @@ impl<'a> Linker for GccLinker<'a> {
     }
 
     fn link_dylib(&mut self, lib: Symbol, verbatim: bool, as_needed: bool) {
+        if self.sess.target.os == "illumos" && lib.as_str() == "c" {
+            // libc will be added via late_link_args on illumos so that it will
+            // appear last in the library search order.
+            // FIXME: This should be replaced by a more complete and generic
+            // mechanism for controlling the order of library arguments passed
+            // to the linker.
+            return;
+        }
         if !as_needed {
             if self.sess.target.is_like_osx {
                 // FIXME(81490): ld64 doesn't support these flags but macOS 11
@@ -813,11 +821,9 @@ impl<'a> Linker for MsvcLinker<'a> {
     }
 
     fn link_whole_staticlib(&mut self, lib: Symbol, verbatim: bool, _search_path: &[PathBuf]) {
-        self.link_staticlib(lib, verbatim);
         self.cmd.arg(format!("/WHOLEARCHIVE:{}{}", lib, if verbatim { "" } else { ".lib" }));
     }
     fn link_whole_rlib(&mut self, path: &Path) {
-        self.link_rlib(path);
         let mut arg = OsString::from("/WHOLEARCHIVE:");
         arg.push(path);
         self.cmd.arg(arg);

compiler/rustc_expand/src/config.rs

@@ -464,31 +464,9 @@ impl<'a> StripUnconfigured<'a> {
                     return true;
                 }
             };
-            let error = |span, msg, suggestion: &str| {
-                let mut err = self.sess.parse_sess.span_diagnostic.struct_span_err(span, msg);
-                if !suggestion.is_empty() {
-                    err.span_suggestion(
-                        span,
-                        "expected syntax is",
-                        suggestion.into(),
-                        Applicability::MaybeIncorrect,
-                    );
-                }
-                err.emit();
-                true
-            };
-            let span = meta_item.span;
-            match meta_item.meta_item_list() {
-                None => error(span, "`cfg` is not followed by parentheses", "cfg(/* predicate */)"),
-                Some([]) => error(span, "`cfg` predicate is not specified", ""),
-                Some([_, .., l]) => error(l.span(), "multiple `cfg` predicates are specified", ""),
-                Some([single]) => match single.meta_item() {
-                    Some(meta_item) => {
-                        attr::cfg_matches(meta_item, &self.sess.parse_sess, self.features)
-                    }
-                    None => error(single.span(), "`cfg` predicate key cannot be a literal", ""),
-                },
-            }
+            parse_cfg(&meta_item, &self.sess).map_or(true, |meta_item| {
+                attr::cfg_matches(&meta_item, &self.sess.parse_sess, self.features)
+            })
         })
     }
 
@@ -532,6 +510,32 @@ impl<'a> StripUnconfigured<'a> {
     }
 }
 
+pub fn parse_cfg<'a>(meta_item: &'a MetaItem, sess: &Session) -> Option<&'a MetaItem> {
+    let error = |span, msg, suggestion: &str| {
+        let mut err = sess.parse_sess.span_diagnostic.struct_span_err(span, msg);
+        if !suggestion.is_empty() {
+            err.span_suggestion(
+                span,
+                "expected syntax is",
+                suggestion.into(),
+                Applicability::HasPlaceholders,
+            );
+        }
+        err.emit();
+        None
+    };
+    let span = meta_item.span;
+    match meta_item.meta_item_list() {
+        None => error(span, "`cfg` is not followed by parentheses", "cfg(/* predicate */)"),
+        Some([]) => error(span, "`cfg` predicate is not specified", ""),
+        Some([_, .., l]) => error(l.span(), "multiple `cfg` predicates are specified", ""),
+        Some([single]) => match single.meta_item() {
+            Some(meta_item) => Some(meta_item),
+            None => error(single.span(), "`cfg` predicate key cannot be a literal", ""),
+        },
+    }
+}
+
 fn is_cfg(sess: &Session, attr: &Attribute) -> bool {
     sess.check_name(attr, sym::cfg)
 }

compiler/rustc_target/src/spec/illumos_base.rs

@@ -6,6 +6,17 @@ pub fn opts() -> TargetOptions {
     late_link_args.insert(
         LinkerFlavor::Gcc,
         vec![
+            // The illumos libc contains a stack unwinding implementation, as
+            // does libgcc_s.  The latter implementation includes several
+            // additional symbols that are not always in base libc.  To force
+            // the consistent use of just one unwinder, we ensure libc appears
+            // after libgcc_s in the NEEDED list for the resultant binary by
+            // ignoring any attempts to add it as a dynamic dependency until the
+            // very end.
+            // FIXME: This should be replaced by a more complete and generic
+            // mechanism for controlling the order of library arguments passed
+            // to the linker.
+            "-lc".to_string(),
             // LLVM will insert calls to the stack protector functions
             // "__stack_chk_fail" and "__stack_chk_guard" into code in native
             // object files.  Some platforms include these symbols directly in

library/std/src/os/unix/process.rs

@@ -75,6 +75,12 @@ pub trait CommandExt: Sealed {
     /// sure that the closure does not violate library invariants by making
     /// invalid use of these duplicates.
     ///
+    /// Panicking in the closure is safe only if all the format arguments for the
+    /// panic message can be safely formatted; this is because although
+    /// `Command` calls [`std::panic::always_abort`](crate::panic::always_abort)
+    /// before calling the pre_exec hook, panic will still try to format the
+    /// panic message.
+    ///
     /// When this closure is run, aspects such as the stdio file descriptors and
     /// working directory have successfully been changed, so output to these
     /// locations may not appear where intended.

library/std/src/panic.rs

@@ -461,5 +461,41 @@ pub fn resume_unwind(payload: Box<dyn Any + Send>) -> ! {
     panicking::rust_panic_without_hook(payload)
 }
 
+/// Make all future panics abort directly without running the panic hook or unwinding.
+///
+/// There is no way to undo this; the effect lasts until the process exits or
+/// execs (or the equivalent).
+///
+/// # Use after fork
+///
+/// This function is particularly useful for calling after `libc::fork`.  After `fork`, in a
+/// multithreaded program it is (on many platforms) not safe to call the allocator.  It is also
+/// generally highly undesirable for an unwind to unwind past the `fork`, because that results in
+/// the unwind propagating to code that was only ever expecting to run in the parent.
+///
+/// `panic::always_abort()` helps avoid both of these.  It directly avoids any further unwinding,
+/// and if there is a panic, the abort will occur without allocating provided that the arguments to
+/// panic can be formatted without allocating.
+///
+/// Examples
+///
+/// ```no_run
+/// #![feature(panic_always_abort)]
+/// use std::panic;
+///
+/// panic::always_abort();
+///
+/// let _ = panic::catch_unwind(|| {
+///     panic!("inside the catch");
+/// });
+///
+/// // We will have aborted already, due to the panic.
+/// unreachable!();
+/// ```
+#[unstable(feature = "panic_always_abort", issue = "84438")]
+pub fn always_abort() {
+    crate::panicking::panic_count::set_always_abort();
+}
+
 #[cfg(test)]
 mod tests;

library/std/src/panicking.rs

@@ -180,7 +180,7 @@ pub fn take_hook() -> Box<dyn Fn(&PanicInfo<'_>) + 'static + Sync + Send> {
 fn default_hook(info: &PanicInfo<'_>) {
     // 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_env = if panic_count::get() >= 2 {
+    let backtrace_env = if panic_count::get_count() >= 2 {
         RustBacktrace::Print(crate::backtrace_rs::PrintFmt::Full)
     } else {
         backtrace::rust_backtrace_env()
@@ -233,6 +233,8 @@ pub mod panic_count {
     use crate::cell::Cell;
     use crate::sync::atomic::{AtomicUsize, Ordering};
 
+    pub const ALWAYS_ABORT_FLAG: usize = 1 << (usize::BITS - 1);
+
     // Panic count for the current thread.
     thread_local! { static LOCAL_PANIC_COUNT: Cell<usize> = Cell::new(0) }
 
@@ -241,33 +243,53 @@ pub mod panic_count {
     // thread, if that thread currently views `GLOBAL_PANIC_COUNT` as being zero,
     // then `LOCAL_PANIC_COUNT` in that thread is zero. This invariant holds before
     // and after increase and decrease, but not necessarily during their execution.
+    //
+    // Additionally, the top bit of GLOBAL_PANIC_COUNT (GLOBAL_ALWAYS_ABORT_FLAG)
+    // records whether panic::always_abort() has been called.  This can only be
+    // set, never cleared.
+    //
+    // This could be viewed as a struct containing a single bit and an n-1-bit
+    // value, but if we wrote it like that it would be more than a single word,
+    // and even a newtype around usize would be clumsy because we need atomics.
+    // But we use such a tuple for the return type of increase().
+    //
+    // Stealing a bit is fine because it just amounts to assuming that each
+    // panicking thread consumes at least 2 bytes of address space.
     static GLOBAL_PANIC_COUNT: AtomicUsize = AtomicUsize::new(0);
 
-    pub fn increase() -> usize {
-        GLOBAL_PANIC_COUNT.fetch_add(1, Ordering::Relaxed);
-        LOCAL_PANIC_COUNT.with(|c| {
-            let next = c.get() + 1;
-            c.set(next);
-            next
-        })
+    pub fn increase() -> (bool, usize) {
+        (
+            GLOBAL_PANIC_COUNT.fetch_add(1, Ordering::Relaxed) & ALWAYS_ABORT_FLAG != 0,
+            LOCAL_PANIC_COUNT.with(|c| {
+                let next = c.get() + 1;
+                c.set(next);
+                next
+            }),
+        )
     }
 
-    pub fn decrease() -> usize {
+    pub fn decrease() {
         GLOBAL_PANIC_COUNT.fetch_sub(1, Ordering::Relaxed);
         LOCAL_PANIC_COUNT.with(|c| {
             let next = c.get() - 1;
             c.set(next);
             next
-        })
+        });
+    }
+
+    pub fn set_always_abort() {
+        GLOBAL_PANIC_COUNT.fetch_or(ALWAYS_ABORT_FLAG, Ordering::Relaxed);
     }
 
-    pub fn get() -> usize {
+    // Disregards ALWAYS_ABORT_FLAG
+    pub fn get_count() -> usize {
         LOCAL_PANIC_COUNT.with(|c| c.get())
     }
 
+    // Disregards ALWAYS_ABORT_FLAG
     #[inline]
-    pub fn is_zero() -> bool {
-        if GLOBAL_PANIC_COUNT.load(Ordering::Relaxed) == 0 {
+    pub fn count_is_zero() -> bool {
+        if GLOBAL_PANIC_COUNT.load(Ordering::Relaxed) & !ALWAYS_ABORT_FLAG == 0 {
             // Fast path: if `GLOBAL_PANIC_COUNT` is zero, all threads
             // (including the current one) will have `LOCAL_PANIC_COUNT`
             // equal to zero, so TLS access can be avoided.
@@ -410,7 +432,7 @@ pub unsafe fn r#try<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>>
 /// Determines whether the current thread is unwinding because of panic.
 #[inline]
 pub fn panicking() -> bool {
-    !panic_count::is_zero()
+    !panic_count::count_is_zero()
 }
 
 /// The entry point for panicking with a formatted message.
@@ -563,15 +585,27 @@ fn rust_panic_with_hook(
     message: Option<&fmt::Arguments<'_>>,
     location: &Location<'_>,
 ) -> ! {
-    let panics = panic_count::increase();
+    let (must_abort, panics) = panic_count::increase();
 
     // If this is the third nested call (e.g., panics == 2, this is 0-indexed),
     // the panic hook probably triggered the last panic, otherwise the
     // double-panic check would have aborted the process. In this case abort the
     // process real quickly as we don't want to try calling it again as it'll
     // probably just panic again.
-    if panics > 2 {
-        util::dumb_print(format_args!("thread panicked while processing panic. aborting.\n"));
+    if must_abort || panics > 2 {
+        if panics > 2 {
+            // Don't try to print the message in this case
+            // - perhaps that is causing the recursive panics.
+            util::dumb_print(format_args!("thread panicked while processing panic. aborting.\n"));
+        } else {
+            // 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);
+            util::dumb_print(format_args!(
+                "{}\npanicked after panic::always_abort(), aborting.\n",
+                panicinfo
+            ));
+        }
         intrinsics::abort()
     }
 

library/std/src/sys/sgx/waitqueue.rs → library/std/src/sys/sgx/waitqueue/mod.rs

@@ -13,13 +13,8 @@
 #[cfg(test)]
 mod tests;
 
-/// A doubly-linked list where callers are in charge of memory allocation
-/// of the nodes in the list.
-mod unsafe_list;
-
-/// Trivial spinlock-based implementation of `sync::Mutex`.
-// FIXME: Perhaps use Intel TSX to avoid locking?
 mod spin_mutex;
+mod unsafe_list;
 
 use crate::num::NonZeroUsize;
 use crate::ops::{Deref, DerefMut};

library/std/src/sys/sgx/waitqueue/spin_mutex.rs

@@ -1,3 +1,6 @@
+//! Trivial spinlock-based implementation of `sync::Mutex`.
+// FIXME: Perhaps use Intel TSX to avoid locking?
+
 #[cfg(test)]
 mod tests;
 

library/std/src/sys/sgx/waitqueue/unsafe_list.rs

@@ -1,3 +1,6 @@
+//! A doubly-linked list where callers are in charge of memory allocation
+//! of the nodes in the list.
+
 #[cfg(test)]
 mod tests;
 

library/std/src/sys/unix/process/process_unix.rs

@@ -54,6 +54,7 @@ impl Command {
         let (env_lock, pid) = unsafe { (sys::os::env_read_lock(), cvt(libc::fork())?) };
 
         if pid == 0 {
+            crate::panic::always_abort();
             mem::forget(env_lock);
             drop(input);
             let Err(err) = unsafe { self.do_exec(theirs, envp.as_ref()) };