Rollup merge of rust-lang#84744 - kornelski:enomem, r=joshtriplett

Add ErrorKind::OutOfMemory

Ability to express `ENOMEM` as an `io::Error`.

I've used `OutOfMemory` as opposed to `NotEnoughMem` or `AllocationFailed`, because "OOM" is used in Rust already.

See also rust-lang#84612

library/std/src/io/error.rs

@@ -186,6 +186,11 @@ pub enum ErrorKind {
     /// This means that the operation can never succeed.
     #[stable(feature = "unsupported_error", since = "1.53.0")]
     Unsupported,
+
+    /// An operation could not be completed, because it failed
+    /// to allocate enough memory.
+    #[stable(feature = "out_of_memory_error", since = "1.53.0")]
+    OutOfMemory,
 }
 
 impl ErrorKind {
@@ -210,6 +215,7 @@ impl ErrorKind {
             ErrorKind::Other => "other os error",
             ErrorKind::UnexpectedEof => "unexpected end of file",
             ErrorKind::Unsupported => "unsupported",
+            ErrorKind::OutOfMemory => "out of memory",
         }
     }
 }

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

@@ -149,6 +149,7 @@ pub fn decode_error_kind(errno: i32) -> ErrorKind {
         libc::ETIMEDOUT => ErrorKind::TimedOut,
         libc::EEXIST => ErrorKind::AlreadyExists,
         libc::ENOSYS => ErrorKind::Unsupported,
+        libc::ENOMEM => ErrorKind::OutOfMemory,
 
         // These two constants can have the same value on some systems,
         // but different values on others, so we can't use a match

library/std/src/sys/wasi/mod.rs

@@ -77,6 +77,7 @@ pub fn decode_error_kind(errno: i32) -> std_io::ErrorKind {
         wasi::ERRNO_EXIST => AlreadyExists,
         wasi::ERRNO_AGAIN => WouldBlock,
         wasi::ERRNO_NOSYS => Unsupported,
+        wasi::ERRNO_NOMEM => OutOfMemory,
         _ => Other,
     }
 }

library/std/src/sys/windows/c.rs

@@ -168,6 +168,8 @@ pub const ERROR_FILE_NOT_FOUND: DWORD = 2;
 pub const ERROR_PATH_NOT_FOUND: DWORD = 3;
 pub const ERROR_ACCESS_DENIED: DWORD = 5;
 pub const ERROR_INVALID_HANDLE: DWORD = 6;
+pub const ERROR_NOT_ENOUGH_MEMORY: DWORD = 8;
+pub const ERROR_OUTOFMEMORY: DWORD = 14;
 pub const ERROR_NO_MORE_FILES: DWORD = 18;
 pub const ERROR_HANDLE_EOF: DWORD = 38;
 pub const ERROR_FILE_EXISTS: DWORD = 80;

library/std/src/sys/windows/mod.rs

@@ -71,6 +71,7 @@ pub fn decode_error_kind(errno: i32) -> ErrorKind {
         c::ERROR_PATH_NOT_FOUND => return ErrorKind::NotFound,
         c::ERROR_NO_DATA => return ErrorKind::BrokenPipe,
         c::ERROR_INVALID_PARAMETER => return ErrorKind::InvalidInput,
+        c::ERROR_NOT_ENOUGH_MEMORY | c::ERROR_OUTOFMEMORY => return ErrorKind::OutOfMemory,
         c::ERROR_SEM_TIMEOUT
         | c::WAIT_TIMEOUT
         | c::ERROR_DRIVER_CANCEL_TIMEOUT