ksupport: raise RuntimeError on reraise with no inflight exception.

Fixes #1123.

artiq/compiler/builtins.py

@@ -169,6 +169,9 @@ def fn_ValueError():
 def fn_ZeroDivisionError():
     return types.TExceptionConstructor(TException("ZeroDivisionError"))
 
+def fn_RuntimeError():
+    return types.TExceptionConstructor(TException("RuntimeError"))
+
 def fn_range():
     return types.TBuiltinFunction("range")
 

artiq/coredevice/comm_kernel.py

@@ -447,7 +447,7 @@ class CommKernel:
                 self._write_string(function)
             else:
                 exn_type = type(exn)
-                if exn_type in (ZeroDivisionError, ValueError, IndexError) or \
+                if exn_type in (ZeroDivisionError, ValueError, IndexError, RuntimeError) or \
                         hasattr(exn, "artiq_builtin"):
                     self._write_string("0:{}".format(exn_type.__name__))
                 else:

artiq/coredevice/exceptions.py

@@ -10,6 +10,7 @@ from artiq.coredevice.runtime import source_loader
 ZeroDivisionError = builtins.ZeroDivisionError
 ValueError = builtins.ValueError
 IndexError = builtins.IndexError
+RuntimeError = builtins.RuntimeError
 
 
 class CoreException:

artiq/firmware/ksupport/eh.rs

@@ -392,7 +392,7 @@ static mut INFLIGHT: ExceptionInfo = ExceptionInfo {
         private:           [0; uw::unwinder_private_data_size],
     },
     exception:      None,
-    handled:        false,
+    handled:        true,
     backtrace:      [0; MAX_BACKTRACE_SIZE],
     backtrace_size: 0
 };
@@ -418,8 +418,22 @@ pub unsafe extern fn raise(exception: *const Exception) -> ! {
 #[export_name="__artiq_reraise"]
 #[unwind(allowed)]
 pub unsafe extern fn reraise() -> ! {
+    use cslice::AsCSlice;
+
     if INFLIGHT.handled {
-        raise(&INFLIGHT.exception.unwrap())
+        match INFLIGHT.exception {
+            Some(ref exception) => raise(exception),
+            None => raise(&Exception {
+                name:     "0:artiq.coredevice.exceptions.RuntimeError".as_c_slice(),
+                file:     file!().as_c_slice(),
+                line:     line!(),
+                column:   column!(),
+                // https://github.com/rust-lang/rfcs/pull/1719
+                function: "__artiq_reraise".as_c_slice(),
+                message:  "No active exception to reraise".as_c_slice(),
+                param:    [0, 0, 0]
+            })
+        }
     } else {
         uw::_Unwind_Resume(&mut INFLIGHT.uw_exception)
     }

artiq/firmware/ksupport/lib.rs

@@ -68,13 +68,13 @@ macro_rules! raise {
     ($name:expr, $message:expr, $param0:expr, $param1:expr, $param2:expr) => ({
         use cslice::AsCSlice;
         let exn = $crate::eh::Exception {
-            name:     concat!("0:artiq.coredevice.exceptions.", $name).as_bytes().as_c_slice(),
-            file:     file!().as_bytes().as_c_slice(),
+            name:     concat!("0:artiq.coredevice.exceptions.", $name).as_c_slice(),
+            file:     file!().as_c_slice(),
             line:     line!(),
             column:   column!(),
             // https://github.com/rust-lang/rfcs/pull/1719
-            function: "(Rust function)".as_bytes().as_c_slice(),
-            message:  $message.as_bytes().as_c_slice(),
+            function: "(Rust function)".as_c_slice(),
+            message:  $message.as_c_slice(),
             param:    [$param0, $param1, $param2]
         };
         #[allow(unused_unsafe)]