py/parse: Fix handling of empty input so it raises an exception.

py/grammar.h

@@ -38,7 +38,7 @@
 // eval_input: testlist NEWLINE* ENDMARKER
 
 DEF_RULE(single_input, nc, or(3), tok(NEWLINE), rule(simple_stmt), rule(compound_stmt))
-DEF_RULE(file_input, nc, and(1), opt_rule(file_input_2))
+DEF_RULE(file_input, c(generic_all_nodes), and(1), opt_rule(file_input_2))
 DEF_RULE(file_input_2, c(generic_all_nodes), one_or_more, rule(file_input_3))
 DEF_RULE(file_input_3, nc, or(2), tok(NEWLINE), rule(stmt))
 DEF_RULE(eval_input, nc, and(2), rule(testlist), opt_rule(eval_input_2))

py/parse.c

@@ -720,6 +720,11 @@ memory_error:
         goto syntax_error;
     }
 
+    // check that parsing resulted in a parse node (can fail on empty input)
+    if (parser.result_stack_top == 0) {
+        goto syntax_error;
+    }
+
     //result_stack_show(parser);
     //printf("rule stack alloc: %d\n", parser.rule_stack_alloc);
     //printf("result stack alloc: %d\n", parser.result_stack_alloc);

tests/basics/parser.py

@@ -0,0 +1,24 @@
+# parser tests
+
+# completely empty string
+# uPy and CPy differ for this case
+#try:
+#    compile("", "stdin", "single")
+#except SyntaxError:
+#    print("SyntaxError")
+try:
+    compile("", "stdin", "eval")
+except SyntaxError:
+    print("SyntaxError")
+compile("", "stdin", "exec")
+
+# empty continued line
+try:
+    compile("\\\n", "stdin", "single")
+except SyntaxError:
+    print("SyntaxError")
+try:
+    compile("\\\n", "stdin", "eval")
+except SyntaxError:
+    print("SyntaxError")
+compile("\\\n", "stdin", "exec")