feat(std): emulate flock for solaris via fcntl

Upstream Solaris flock emulation to libstd from cargo.

This is borrowed from
https://github.com/rust-lang/cargo/blob/3b379fcc541b39321a7758552d37e5e0cc4277b9/src/cargo/util/flock.rs#L502-L536
which was implemented by an Oracle employee.
The code has been in cargo since 2022-12.

Python's `fcntl.flock` emulates like this as well:
https://github.com/python/cpython/blob/c919d02edecfe9d75fe374756fb8aa1db8d95f55/Modules/fcntlmodule.c#L337-L400

We did the same thing in
https://github.com/rust-lang/rust/blob/0d0f4eac8b98133e5da6d3604d86a8f3b5a67844/compiler/rustc_data_structures/src/flock/unix.rs#L13-L39

Author: weihanglo

library/std/src/fs/tests.rs

@@ -226,6 +226,7 @@ fn file_test_io_seek_and_write() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_multiple_shared() {
@@ -249,6 +250,7 @@ fn file_lock_multiple_shared() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_blocking() {
@@ -273,6 +275,7 @@ fn file_lock_blocking() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_drop() {
@@ -294,6 +297,7 @@ fn file_lock_drop() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_dup() {

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

@@ -1293,13 +1293,19 @@ impl File {
         return Ok(());
     }
 
+    #[cfg(any(target_os = "solaris",))]
+    pub fn lock(&self) -> io::Result<()> {
+        self.emulate_flock(libc::F_WRLCK, libc::F_SETLK);
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn lock(&self) -> io::Result<()> {
@@ -1320,13 +1326,19 @@ impl File {
         return Ok(());
     }
 
+    #[cfg(any(target_os = "solaris",))]
+    pub fn lock_shared(&self) -> io::Result<()> {
+        self.emulate_flock(libc::F_RDLCK, libc::F_SETLK);
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn lock_shared(&self) -> io::Result<()> {
@@ -1355,13 +1367,28 @@ impl File {
         }
     }
 
+    #[cfg(any(target_os = "solaris",))]
+    pub fn try_lock(&self) -> io::Result<()> {
+        let result = self.emulate_flock(libc::F_WRLCK, libc::F_SETLKW);
+        if let Err(err) = result {
+            if err.kind() == io::ErrorKind::WouldBlock {
+                Err(TryLockError::WouldBlock)
+            } else {
+                Err(TryLockError::Error(err))
+            }
+        } else {
+            Ok(())
+        }
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn try_lock(&self) -> Result<(), TryLockError> {
@@ -1393,13 +1420,28 @@ impl File {
         }
     }
 
+    #[cfg(any(target_os = "solaris",))]
+    pub fn try_lock_shared(&self) -> io::Result<()> {
+        let result = self.emulate_flock(libc::F_RDLCK, libc::F_SETLKW);
+        if let Err(err) = result {
+            if err.kind() == io::ErrorKind::WouldBlock {
+                Err(TryLockError::WouldBlock)
+            } else {
+                Err(TryLockError::Error(err))
+            }
+        } else {
+            Ok(())
+        }
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn try_lock_shared(&self) -> Result<(), TryLockError> {
@@ -1423,19 +1465,34 @@ impl File {
         return Ok(());
     }
 
+    #[cfg(any(target_os = "solaris",))]
+    pub fn unlock(&self) -> io::Result<()> {
+        self.emulate_flock(libc::F_UNLCK, libc::F_SETLK)
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn unlock(&self) -> io::Result<()> {
         Err(io::const_error!(io::ErrorKind::Unsupported, "unlock() not supported"))
     }
 
+    /// Emulates flock by `fcntl`.
+    #[cfg(any(target_os = "solaris",))]
+    fn emulate_flock(&self, lock_type: libc::c_int, cmd: libc::c_int) -> Result<()> {
+        let mut flock: libc::flock = unsafe { mem::zeroed() };
+        flock.l_whence = libc::SEEK_SET;
+        flock.l_type = lock_type;
+        cvt(unsafe { libc::fcntl(file.as_raw_fd(), cmd, &flock) })
+    }
+
     pub fn truncate(&self, size: u64) -> io::Result<()> {
         let size: off64_t =
             size.try_into().map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;