std: Unsafe-wrap backtrace code held in-common

Author: workingjubilee

std/src/sys/backtrace.rs

@@ -1,4 +1,5 @@
 //! Common code for printing backtraces.
+#![forbid(unsafe_op_in_unsafe_fn)]
 
 use crate::backtrace_rs::{self, BacktraceFmt, BytesOrWideString, PrintFmt};
 use crate::borrow::Cow;
@@ -62,73 +63,76 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
     // Start immediately if we're not using a short backtrace.
     let mut start = print_fmt != PrintFmt::Short;
     set_image_base();
-    backtrace_rs::trace_unsynchronized(|frame| {
-        if print_fmt == PrintFmt::Short && idx > MAX_NB_FRAMES {
-            return false;
-        }
+    // SAFETY: we roll our own locking in this town
+    unsafe {
+        backtrace_rs::trace_unsynchronized(|frame| {
+            if print_fmt == PrintFmt::Short && idx > MAX_NB_FRAMES {
+                return false;
+            }
 
-        let mut hit = false;
-        backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
-            hit = true;
-
-            // Any frames between `__rust_begin_short_backtrace` and `__rust_end_short_backtrace`
-            // are omitted from the backtrace in short mode, `__rust_end_short_backtrace` will be
-            // called before the panic hook, so we won't ignore any frames if there is no
-            // invoke of `__rust_begin_short_backtrace`.
-            if print_fmt == PrintFmt::Short {
-                if let Some(sym) = symbol.name().and_then(|s| s.as_str()) {
-                    if start && sym.contains("__rust_begin_short_backtrace") {
-                        start = false;
-                        return;
-                    }
-                    if sym.contains("__rust_end_short_backtrace") {
-                        start = true;
-                        return;
-                    }
-                    if !start {
-                        omitted_count += 1;
+            let mut hit = false;
+            backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
+                hit = true;
+
+                // Any frames between `__rust_begin_short_backtrace` and `__rust_end_short_backtrace`
+                // are omitted from the backtrace in short mode, `__rust_end_short_backtrace` will be
+                // called before the panic hook, so we won't ignore any frames if there is no
+                // invoke of `__rust_begin_short_backtrace`.
+                if print_fmt == PrintFmt::Short {
+                    if let Some(sym) = symbol.name().and_then(|s| s.as_str()) {
+                        if start && sym.contains("__rust_begin_short_backtrace") {
+                            start = false;
+                            return;
+                        }
+                        if sym.contains("__rust_end_short_backtrace") {
+                            start = true;
+                            return;
+                        }
+                        if !start {
+                            omitted_count += 1;
+                        }
                     }
                 }
-            }
 
-            if start {
-                if omitted_count > 0 {
-                    debug_assert!(print_fmt == PrintFmt::Short);
-                    // only print the message between the middle of frames
-                    if !first_omit {
-                        let _ = writeln!(
-                            bt_fmt.formatter(),
-                            "      [... omitted {} frame{} ...]",
-                            omitted_count,
-                            if omitted_count > 1 { "s" } else { "" }
-                        );
+                if start {
+                    if omitted_count > 0 {
+                        debug_assert!(print_fmt == PrintFmt::Short);
+                        // only print the message between the middle of frames
+                        if !first_omit {
+                            let _ = writeln!(
+                                bt_fmt.formatter(),
+                                "      [... omitted {} frame{} ...]",
+                                omitted_count,
+                                if omitted_count > 1 { "s" } else { "" }
+                            );
+                        }
+                        first_omit = false;
+                        omitted_count = 0;
                     }
-                    first_omit = false;
-                    omitted_count = 0;
+                    res = bt_fmt.frame().symbol(frame, symbol);
                 }
-                res = bt_fmt.frame().symbol(frame, symbol);
+            });
+            #[cfg(target_os = "nto")]
+            if libc::__my_thread_exit as *mut libc::c_void == frame.ip() {
+                if !hit && start {
+                    use crate::backtrace_rs::SymbolName;
+                    res = bt_fmt.frame().print_raw(
+                        frame.ip(),
+                        Some(SymbolName::new("__my_thread_exit".as_bytes())),
+                        None,
+                        None,
+                    );
+                }
+                return false;
             }
-        });
-        #[cfg(target_os = "nto")]
-        if libc::__my_thread_exit as *mut libc::c_void == frame.ip() {
             if !hit && start {
-                use crate::backtrace_rs::SymbolName;
-                res = bt_fmt.frame().print_raw(
-                    frame.ip(),
-                    Some(SymbolName::new("__my_thread_exit".as_bytes())),
-                    None,
-                    None,
-                );
+                res = bt_fmt.frame().print_raw(frame.ip(), None, None, None);
             }
-            return false;
-        }
-        if !hit && start {
-            res = bt_fmt.frame().print_raw(frame.ip(), None, None, None);
-        }
 
-        idx += 1;
-        res.is_ok()
-    });
+            idx += 1;
+            res.is_ok()
+        })
+    };
     res?;
     bt_fmt.finish()?;
     if print_fmt == PrintFmt::Short {