Fix new function_casts_as_integer lint errors in std

Author: GuillaumeGomez

compiler/rustc_lint/src/function_cast_as_integer.rs

@@ -23,7 +23,6 @@ declare_lint! {
     /// You should never cast a function directly into an integer but go through
     /// a cast as `fn` first to make it obvious what's going on. It also allows
     /// to prevent confusion with (associated) constants.
-    /// ```
     pub FUNCTION_CASTS_AS_INTEGER,
     Warn,
     "Casting a function into an integer",

library/std/src/backtrace.rs

@@ -293,7 +293,7 @@ impl Backtrace {
         if !Backtrace::enabled() {
             return Backtrace { inner: Inner::Disabled };
         }
-        Backtrace::create(Backtrace::capture as usize)
+        Backtrace::create(Backtrace::capture as fn() -> Backtrace as usize)
     }
 
     /// Forcibly captures a full backtrace, regardless of environment variable
@@ -309,7 +309,7 @@ impl Backtrace {
     #[stable(feature = "backtrace", since = "1.65.0")]
     #[inline(never)] // want to make sure there's a frame here to remove
     pub fn force_capture() -> Backtrace {
-        Backtrace::create(Backtrace::force_capture as usize)
+        Backtrace::create(Backtrace::force_capture as fn() -> Backtrace as usize)
     }
 
     /// Forcibly captures a disabled backtrace, regardless of environment

library/std/src/sys/pal/unix/stack_overflow.rs

@@ -169,7 +169,9 @@ mod imp {
                 }
 
                 action.sa_flags = SA_SIGINFO | SA_ONSTACK;
-                action.sa_sigaction = signal_handler as sighandler_t;
+                action.sa_sigaction = signal_handler
+                    as unsafe extern "C" fn(i32, *mut libc::siginfo_t, *mut libc::c_void)
+                    as sighandler_t;
                 // SAFETY: only overriding signals if the default is set
                 unsafe { sigaction(signal, &action, ptr::null_mut()) };
             }