remove prctl, now that std does not use it any more

it is a terrible variadic function...

Author: RalfJung

src/shims/unix/linux/foreign_items.rs

@@ -51,12 +51,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             }
 
             // Threading
-            "prctl" => {
-                // prctl is variadic. (It is not documented like that in the manpage, but defined like that in the libc crate.)
-                this.check_abi_and_shim_symbol_clash(abi, Abi::C { unwind: false }, link_name)?;
-                let result = this.prctl(args)?;
-                this.write_scalar(Scalar::from_i32(result), dest)?;
-            }
             "pthread_condattr_setclock" => {
                 let [attr, clock_id] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;

src/shims/unix/thread.rs

@@ -107,53 +107,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         Ok(Scalar::from_u32(0))
     }
 
-    fn prctl(&mut self, args: &[OpTy<'tcx, Provenance>]) -> InterpResult<'tcx, i32> {
-        let this = self.eval_context_mut();
-        this.assert_target_os("linux", "prctl");
-
-        if args.is_empty() {
-            throw_ub_format!(
-                "incorrect number of arguments for `prctl`: got {}, expected at least 1",
-                args.len()
-            );
-        }
-
-        let option = this.read_scalar(&args[0])?.to_i32()?;
-        if option == this.eval_libc_i32("PR_SET_NAME")? {
-            if args.len() < 2 {
-                throw_ub_format!(
-                    "incorrect number of arguments for `prctl` with `PR_SET_NAME`: got {}, expected at least 2",
-                    args.len()
-                );
-            }
-
-            let address = this.read_pointer(&args[1])?;
-            let mut name = this.read_c_str(address)?.to_owned();
-            // The name should be no more than 16 bytes, including the null
-            // byte. Since `read_c_str` returns the string without the null
-            // byte, we need to truncate to 15.
-            name.truncate(15);
-            this.set_thread_name(this.get_active_thread(), name);
-        } else if option == this.eval_libc_i32("PR_GET_NAME")? {
-            if args.len() < 2 {
-                throw_ub_format!(
-                    "incorrect number of arguments for `prctl` with `PR_SET_NAME`: got {}, expected at least 2",
-                    args.len()
-                );
-            }
-
-            let address = this.read_pointer(&args[1])?;
-            let mut name = this.get_thread_name(this.get_active_thread()).to_vec();
-            name.push(0u8);
-            assert!(name.len() <= 16);
-            this.write_bytes_ptr(address, name)?;
-        } else {
-            throw_unsup_format!("unsupported prctl option {}", option);
-        }
-
-        Ok(0)
-    }
-
     fn sched_yield(&mut self) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();
 

tests/pass/libc.rs

@@ -277,58 +277,6 @@ fn test_rwlock_libc_static_initializer() {
     }
 }
 
-/// Test whether the `prctl` shim correctly sets the thread name.
-///
-/// Note: `prctl` exists only on Linux.
-#[cfg(any(target_os = "linux"))]
-fn test_prctl_thread_name() {
-    use libc::c_long;
-    use std::ffi::CString;
-    unsafe {
-        let mut buf = [255; 10];
-        assert_eq!(
-            libc::prctl(libc::PR_GET_NAME, buf.as_mut_ptr(), 0 as c_long, 0 as c_long, 0 as c_long),
-            0,
-        );
-        // Rust runtime might set thread name, so we allow two options here.
-        assert!(&buf[..10] == b"<unnamed>\0" || &buf[..5] == b"main\0");
-        let thread_name = CString::new("hello").expect("CString::new failed");
-        assert_eq!(
-            libc::prctl(
-                libc::PR_SET_NAME,
-                thread_name.as_ptr(),
-                0 as c_long,
-                0 as c_long,
-                0 as c_long,
-            ),
-            0,
-        );
-        let mut buf = [255; 6];
-        assert_eq!(
-            libc::prctl(libc::PR_GET_NAME, buf.as_mut_ptr(), 0 as c_long, 0 as c_long, 0 as c_long),
-            0,
-        );
-        assert_eq!(b"hello\0", &buf);
-        let long_thread_name = CString::new("01234567890123456789").expect("CString::new failed");
-        assert_eq!(
-            libc::prctl(
-                libc::PR_SET_NAME,
-                long_thread_name.as_ptr(),
-                0 as c_long,
-                0 as c_long,
-                0 as c_long,
-            ),
-            0,
-        );
-        let mut buf = [255; 16];
-        assert_eq!(
-            libc::prctl(libc::PR_GET_NAME, buf.as_mut_ptr(), 0 as c_long, 0 as c_long, 0 as c_long),
-            0,
-        );
-        assert_eq!(b"012345678901234\0", &buf);
-    }
-}
-
 /// Tests whether each thread has its own `__errno_location`.
 fn test_thread_local_errno() {
     #[cfg(target_os = "linux")]
@@ -473,9 +421,6 @@ fn main() {
     #[cfg(any(target_os = "linux"))]
     test_mutex_libc_static_initializer_recursive();
 
-    #[cfg(any(target_os = "linux"))]
-    test_prctl_thread_name();
-
     test_thread_local_errno();
 
     #[cfg(any(target_os = "linux"))]