fix setting thread name on macOS

Author: RalfJung

src/shims/foreign_items/posix/macos.rs

@@ -98,6 +98,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.write_scalar(stack_size, dest)?;
             }
 
+            // Threading
+            "pthread_setname_np" => {
+                let ptr = this.read_scalar(args[0])?.not_undef()?;
+                this.pthread_setname_np(ptr)?;
+            }
+
             // Incomplete shims that we "stub out" just to get pre-main initialization code to work.
             // These shims are enabled only when the caller is in the standard library.
             "mmap" if this.frame().instance.to_string().starts_with("std::sys::unix::") => {

src/shims/thread.rs

@@ -95,6 +95,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         _arg5: OpTy<'tcx, Tag>,
     ) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();
+        this.assert_target_os("linux", "prctl");
 
         let option = this.read_scalar(option)?.to_i32()?;
         if option == this.eval_libc_i32("PR_SET_NAME")? {
@@ -118,6 +119,19 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         Ok(0)
     }
 
+    fn pthread_setname_np(
+        &mut self,
+        ptr: Scalar<Tag>,
+    ) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+        this.assert_target_os("macos", "pthread_setname_np");
+
+        let name = this.memory.read_c_str(ptr)?.to_owned();
+        this.set_active_thread_name(name)?;
+
+        Ok(())
+    }
+
     fn sched_yield(&mut self) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();