Rollup merge of rust-lang#109784 - beetrees:riscv32-time64, r=cuviper

Refactor glibc time64 support, riscv32 always has 64-bit `time_t`

Refactor existing support for 64-bit `time_t` on 32-bit glibc platforms, as riscv32 `time_t` is 64-bit by default. Split out of rust-lang#109773.

Author: matthiaskrgr

library/std/src/sys/unix/time.rs

@@ -174,6 +174,34 @@ impl From<libc::timespec> for Timespec {
     }
 }
 
+#[cfg(all(
+    target_os = "linux",
+    target_env = "gnu",
+    target_pointer_width = "32",
+    not(target_arch = "riscv32")
+))]
+#[repr(C)]
+pub(in crate::sys::unix) struct __timespec64 {
+    pub(in crate::sys::unix) tv_sec: i64,
+    #[cfg(target_endian = "big")]
+    _padding: i32,
+    pub(in crate::sys::unix) tv_nsec: i32,
+    #[cfg(target_endian = "little")]
+    _padding: i32,
+}
+
+#[cfg(all(
+    target_os = "linux",
+    target_env = "gnu",
+    target_pointer_width = "32",
+    not(target_arch = "riscv32")
+))]
+impl From<__timespec64> for Timespec {
+    fn from(t: __timespec64) -> Timespec {
+        Timespec::new(t.tv_sec, t.tv_nsec.into())
+    }
+}
+
 #[cfg(any(
     all(target_os = "macos", any(not(target_arch = "aarch64"))),
     target_os = "ios",
@@ -352,29 +380,23 @@ mod inner {
     impl Timespec {
         pub fn now(clock: libc::clockid_t) -> Timespec {
             // Try to use 64-bit time in preparation for Y2038.
-            #[cfg(all(target_os = "linux", target_env = "gnu", target_pointer_width = "32"))]
+            #[cfg(all(
+                target_os = "linux",
+                target_env = "gnu",
+                target_pointer_width = "32",
+                not(target_arch = "riscv32")
+            ))]
             {
                 use crate::sys::weak::weak;
 
                 // __clock_gettime64 was added to 32-bit arches in glibc 2.34,
                 // and it handles both vDSO calls and ENOSYS fallbacks itself.
-                weak!(fn __clock_gettime64(libc::clockid_t, *mut __timespec64) -> libc::c_int);
-
-                #[repr(C)]
-                struct __timespec64 {
-                    tv_sec: i64,
-                    #[cfg(target_endian = "big")]
-                    _padding: i32,
-                    tv_nsec: i32,
-                    #[cfg(target_endian = "little")]
-                    _padding: i32,
-                }
+                weak!(fn __clock_gettime64(libc::clockid_t, *mut super::__timespec64) -> libc::c_int);
 
                 if let Some(clock_gettime64) = __clock_gettime64.get() {
                     let mut t = MaybeUninit::uninit();
                     cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();
-                    let t = unsafe { t.assume_init() };
-                    return Timespec::new(t.tv_sec, t.tv_nsec as i64);
+                    return Timespec::from(unsafe { t.assume_init() });
                 }
             }