Print an error when a data statement passes the end of memory

hera/preprocessor.py

@@ -6,7 +6,7 @@
 from lark import Token
 
 from .parser import Op
-from .utils import copy_token, HERAError, is_symbol, to_u16
+from .utils import copy_token, emit_error, HERAError, is_symbol, to_u16
 
 
 # Arbitrary value copied over from HERA-C.
@@ -58,21 +58,24 @@ def get_labels(program):
     pc = 0
     dc = HERA_DATA_START
     for op in program:
-        opname = op.name.lower()
-        if opname == "label":
+        odc = dc
+        if op.name == "LABEL":
             labels[op.args[0]] = pc
-        elif opname == "dlabel":
+        elif op.name == "DLABEL":
             labels[op.args[0]] = dc
-        elif opname == "constant":
+        elif op.name == "CONSTANT":
             labels[op.args[0]] = op.args[1]
-        elif opname == "integer":
+        elif op.name == "INTEGER":
             dc += 1
-        elif opname == "dskip":
+        elif op.name == "DSKIP":
             dc += op.args[0]
-        elif opname == "lp_string":
+        elif op.name == "LP_STRING":
             dc += len(op.args[0]) + 1
         else:
             pc += 1
+
+        if dc >= 0xFFFF and odc < 0xFFFF:
+            emit_error("past the end of available memory", line=op.name.line)
     return labels
 
 

test/assets/dskip_overflow.hera

@@ -0,0 +1,5 @@
+DSKIP(0xFFFF)
+DLABEL(N)
+INTEGER(42)
+
+SET(R1, N)

test/test_integration.py

@@ -163,6 +163,16 @@ def test_hera_boilerplate_dot_hera():
     assert not vm.flag_carry_block
 
 
+def test_dskip_overflow_dot_hera(capsys):
+    vm = VirtualMachine()
+    with pytest.raises(SystemExit):
+        main(["test/assets/dskip_overflow.hera"], vm)
+
+    captured = capsys.readouterr()
+    assert "DSKIP(0xFFFF)" in captured.err
+    assert "line 1" in captured.err
+
+
 def test_error_message_for_missing_comma(capsys):
     line = "SETLO(R1 40)"
     with pytest.raises(SystemExit):