Auto merge of #96657 - cuviper:time64, r=joshtriplett

Use 64-bit time on 32-bit linux-gnu

The standard library suffered the [Year 2038 problem][Y2038] in two main places on targets with 32-bit `time_t`:

- In `std::time::SystemTime`, we stored a `timespec` that has `time_t` seconds. This is now changed to directly store 64-bit seconds and nanoseconds, and on 32-bit linux-gnu we try to use `__clock_gettime64` (glibc 2.34+) to get the larger timestamp.

- In `std::fs::Metadata`, we store a `stat64`, which has 64-bit `off_t` but still 32-bit `time_t`, and unfortunately that is baked in the API by the (deprecated) `MetadataExt::as_raw_stat()`. However, we can use `statx` for 64-bit `statx_timestamp` to store in addition to the `stat64`, as we already do to support creation time, and the rest of the `MetadataExt` methods can return those full values. Note that some filesystems may still be limited in their actual timestamp support, but that's not something Rust can change.

There remain a few places that need `timespec` for system call timeouts -- I leave that to future work.

[Y2038]: https://en.wikipedia.org/wiki/Year_2038_problem

Author: bors

library/std/src/os/linux/fs.rs

@@ -356,19 +356,34 @@ impl MetadataExt for Metadata {
         self.as_inner().as_inner().st_size as u64
     }
     fn st_atime(&self) -> i64 {
-        self.as_inner().as_inner().st_atime as i64
+        let file_attr = self.as_inner();
+        #[cfg(all(target_env = "gnu", target_pointer_width = "32"))]
+        if let Some(atime) = file_attr.stx_atime() {
+            return atime.tv_sec;
+        }
+        file_attr.as_inner().st_atime as i64
     }
     fn st_atime_nsec(&self) -> i64 {
         self.as_inner().as_inner().st_atime_nsec as i64
     }
     fn st_mtime(&self) -> i64 {
-        self.as_inner().as_inner().st_mtime as i64
+        let file_attr = self.as_inner();
+        #[cfg(all(target_env = "gnu", target_pointer_width = "32"))]
+        if let Some(mtime) = file_attr.stx_mtime() {
+            return mtime.tv_sec;
+        }
+        file_attr.as_inner().st_mtime as i64
     }
     fn st_mtime_nsec(&self) -> i64 {
         self.as_inner().as_inner().st_mtime_nsec as i64
     }
     fn st_ctime(&self) -> i64 {
-        self.as_inner().as_inner().st_ctime as i64
+        let file_attr = self.as_inner();
+        #[cfg(all(target_env = "gnu", target_pointer_width = "32"))]
+        if let Some(ctime) = file_attr.stx_ctime() {
+            return ctime.tv_sec;
+        }
+        file_attr.as_inner().st_ctime as i64
     }
     fn st_ctime_nsec(&self) -> i64 {
         self.as_inner().as_inner().st_ctime_nsec as i64

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

@@ -113,10 +113,19 @@ cfg_has_statx! {{
         // This is needed to check if btime is supported by the filesystem.
         stx_mask: u32,
         stx_btime: libc::statx_timestamp,
+        // With statx, we can overcome 32-bit `time_t` too.
+        #[cfg(target_pointer_width = "32")]
+        stx_atime: libc::statx_timestamp,
+        #[cfg(target_pointer_width = "32")]
+        stx_ctime: libc::statx_timestamp,
+        #[cfg(target_pointer_width = "32")]
+        stx_mtime: libc::statx_timestamp,
+
     }
 
-    // We prefer `statx` on Linux if available, which contains file creation time.
-    // Default `stat64` contains no creation time.
+    // We prefer `statx` on Linux if available, which contains file creation time,
+    // as well as 64-bit timestamps of all kinds.
+    // Default `stat64` contains no creation time and may have 32-bit `time_t`.
     unsafe fn try_statx(
         fd: c_int,
         path: *const c_char,
@@ -192,6 +201,13 @@ cfg_has_statx! {{
         let extra = StatxExtraFields {
             stx_mask: buf.stx_mask,
             stx_btime: buf.stx_btime,
+            // Store full times to avoid 32-bit `time_t` truncation.
+            #[cfg(target_pointer_width = "32")]
+            stx_atime: buf.stx_atime,
+            #[cfg(target_pointer_width = "32")]
+            stx_ctime: buf.stx_ctime,
+            #[cfg(target_pointer_width = "32")]
+            stx_mtime: buf.stx_mtime,
         };
 
         Some(Ok(FileAttr { stat, statx_extra_fields: Some(extra) }))
@@ -310,6 +326,36 @@ cfg_has_statx! {{
         fn from_stat64(stat: stat64) -> Self {
             Self { stat, statx_extra_fields: None }
         }
+
+        #[cfg(target_pointer_width = "32")]
+        pub fn stx_mtime(&self) -> Option<&libc::statx_timestamp> {
+            if let Some(ext) = &self.statx_extra_fields {
+                if (ext.stx_mask & libc::STATX_MTIME) != 0 {
+                    return Some(&ext.stx_mtime);
+                }
+            }
+            None
+        }
+
+        #[cfg(target_pointer_width = "32")]
+        pub fn stx_atime(&self) -> Option<&libc::statx_timestamp> {
+            if let Some(ext) = &self.statx_extra_fields {
+                if (ext.stx_mask & libc::STATX_ATIME) != 0 {
+                    return Some(&ext.stx_atime);
+                }
+            }
+            None
+        }
+
+        #[cfg(target_pointer_width = "32")]
+        pub fn stx_ctime(&self) -> Option<&libc::statx_timestamp> {
+            if let Some(ext) = &self.statx_extra_fields {
+                if (ext.stx_mask & libc::STATX_CTIME) != 0 {
+                    return Some(&ext.stx_ctime);
+                }
+            }
+            None
+        }
     }
 } else {
     impl FileAttr {
@@ -335,59 +381,52 @@ impl FileAttr {
 #[cfg(target_os = "netbsd")]
 impl FileAttr {
     pub fn modified(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_mtime as libc::time_t,
-            tv_nsec: self.stat.st_mtimensec as libc::c_long,
-        }))
+        Ok(SystemTime::new(self.stat.st_mtime as i64, self.stat.st_mtimensec as i64))
     }
 
     pub fn accessed(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_atime as libc::time_t,
-            tv_nsec: self.stat.st_atimensec as libc::c_long,
-        }))
+        Ok(SystemTime::new(self.stat.st_atime as i64, self.stat.st_atimensec as i64))
     }
 
     pub fn created(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_birthtime as libc::time_t,
-            tv_nsec: self.stat.st_birthtimensec as libc::c_long,
-        }))
+        Ok(SystemTime::new(self.stat.st_birthtime as i64, self.stat.st_birthtimensec as i64))
     }
 }
 
 #[cfg(not(target_os = "netbsd"))]
 impl FileAttr {
     #[cfg(all(not(target_os = "vxworks"), not(target_os = "espidf")))]
     pub fn modified(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_mtime as libc::time_t,
-            tv_nsec: self.stat.st_mtime_nsec as _,
-        }))
+        #[cfg(target_pointer_width = "32")]
+        cfg_has_statx! {
+            if let Some(mtime) = self.stx_mtime() {
+                return Ok(SystemTime::new(mtime.tv_sec, mtime.tv_nsec as i64));
+            }
+        }
+
+        Ok(SystemTime::new(self.stat.st_mtime as i64, self.stat.st_mtime_nsec as i64))
     }
 
     #[cfg(any(target_os = "vxworks", target_os = "espidf"))]
     pub fn modified(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_mtime as libc::time_t,
-            tv_nsec: 0,
-        }))
+        Ok(SystemTime::new(self.stat.st_mtime as i64, 0))
     }
 
     #[cfg(all(not(target_os = "vxworks"), not(target_os = "espidf")))]
     pub fn accessed(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_atime as libc::time_t,
-            tv_nsec: self.stat.st_atime_nsec as _,
-        }))
+        #[cfg(target_pointer_width = "32")]
+        cfg_has_statx! {
+            if let Some(atime) = self.stx_atime() {
+                return Ok(SystemTime::new(atime.tv_sec, atime.tv_nsec as i64));
+            }
+        }
+
+        Ok(SystemTime::new(self.stat.st_atime as i64, self.stat.st_atime_nsec as i64))
     }
 
     #[cfg(any(target_os = "vxworks", target_os = "espidf"))]
     pub fn accessed(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_atime as libc::time_t,
-            tv_nsec: 0,
-        }))
+        Ok(SystemTime::new(self.stat.st_atime as i64, 0))
     }
 
     #[cfg(any(
@@ -397,10 +436,7 @@ impl FileAttr {
         target_os = "ios"
     ))]
     pub fn created(&self) -> io::Result<SystemTime> {
-        Ok(SystemTime::from(libc::timespec {
-            tv_sec: self.stat.st_birthtime as libc::time_t,
-            tv_nsec: self.stat.st_birthtime_nsec as libc::c_long,
-        }))
+        Ok(SystemTime::new(self.stat.st_birthtime as i64, self.stat.st_birthtime_nsec as i64))
     }
 
     #[cfg(not(any(
@@ -413,10 +449,7 @@ impl FileAttr {
         cfg_has_statx! {
             if let Some(ext) = &self.statx_extra_fields {
                 return if (ext.stx_mask & libc::STATX_BTIME) != 0 {
-                    Ok(SystemTime::from(libc::timespec {
-                        tv_sec: ext.stx_btime.tv_sec as libc::time_t,
-                        tv_nsec: ext.stx_btime.tv_nsec as _,
-                    }))
+                    Ok(SystemTime::new(ext.stx_btime.tv_sec, ext.stx_btime.tv_nsec as i64))
                 } else {
                     Err(io::const_io_error!(
                         io::ErrorKind::Uncategorized,

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

@@ -24,8 +24,9 @@ pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option<Duration>) -
     // Calculate the timeout as an absolute timespec.
     //
     // Overflows are rounded up to an infinite timeout (None).
-    let timespec =
-        timeout.and_then(|d| Some(Timespec::now(libc::CLOCK_MONOTONIC).checked_add_duration(&d)?));
+    let timespec = timeout
+        .and_then(|d| Some(Timespec::now(libc::CLOCK_MONOTONIC).checked_add_duration(&d)?))
+        .and_then(|t| t.to_timespec());
 
     loop {
         // No need to wait if the value already changed.
@@ -41,7 +42,7 @@ pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option<Duration>) -
                     // identical. It supports absolute timeouts through a flag
                     // in the _umtx_time struct.
                     let umtx_timeout = timespec.map(|t| libc::_umtx_time {
-                        _timeout: t.t,
+                        _timeout: t,
                         _flags: libc::UMTX_ABSTIME,
                         _clockid: libc::CLOCK_MONOTONIC as u32,
                     });
@@ -62,7 +63,7 @@ pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option<Duration>) -
                         futex as *const AtomicU32,
                         libc::FUTEX_WAIT_BITSET | libc::FUTEX_PRIVATE_FLAG,
                         expected,
-                        timespec.as_ref().map_or(null(), |t| &t.t as *const libc::timespec),
+                        timespec.as_ref().map_or(null(), |t| t as *const libc::timespec),
                         null::<u32>(), // This argument is unused for FUTEX_WAIT_BITSET.
                         !0u32,         // A full bitmask, to make it behave like a regular FUTEX_WAIT.
                     )

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

@@ -79,7 +79,8 @@ unsafe fn wait_timeout(
         (Timespec::now(libc::CLOCK_MONOTONIC), dur)
     };
 
-    let timeout = now.checked_add_duration(&dur).map(|t| t.t).unwrap_or(TIMESPEC_MAX);
+    let timeout =
+        now.checked_add_duration(&dur).and_then(|t| t.to_timespec()).unwrap_or(TIMESPEC_MAX);
     let r = libc::pthread_cond_timedwait(cond, lock, &timeout);
     debug_assert!(r == libc::ETIMEDOUT || r == 0);
 }