Added some tests and error checking for return stack over and underflow.

Author: strinsberg

include/ltconst.h

@@ -36,5 +36,7 @@ extern const size_t EXIT_POB;
 extern const size_t EXIT_OP;
 extern const size_t EXIT_STR;
 extern const size_t EXIT_ARGS;
+extern const size_t EXIT_RSOF;
+extern const size_t EXIT_RSUF;
 
 #endif

src/ltconst.c

@@ -42,4 +42,6 @@ const size_t EXIT_POB = 6;
 const size_t EXIT_OP = 7;
 const size_t EXIT_STR = 8;
 const size_t EXIT_ARGS = 9;
+const size_t EXIT_RSOF = 10;
+const size_t EXIT_RSUF = 11;
 

src/ltrun.c

@@ -27,12 +27,20 @@ size_t execute(WORD* memory, size_t length, WORD* data_stack, WORD* return_stack
               "Error: program counter out of bounds, pc: %hx, bfp: %hd\n",
               pc, bfp);
       exit (EXIT_POB);
-    } else if (dsp > 0x8000) {  // i.e. it has wrapped around into negative numbers
+    } else if (dsp > 0x8000) {  // i.e. it has wrapped around into negatives
       fprintf(stderr, "Error: stack underflow, sp: %hx or %hd\n", dsp, dsp);
       exit (EXIT_SUF);
     } else if (dsp > END_STACK) {
       fprintf(stderr, "Error: stack overflow, sp: %hx or %hd\n", dsp, dsp);
       exit (EXIT_SOF);
+    } else if (rsp > 0x8000) {  // i.e. it has wrapped around into negatives
+      fprintf(stderr, "Error: return stack underflow, sp: %hx or %hd\n",
+              rsp, rsp);
+      exit (EXIT_RSUF);
+    } else if (rsp > END_RETURN) {
+      fprintf(stderr, "Error: return stack overflow, sp: %hx or %hd\n",
+              rsp, rsp);
+      exit (EXIT_RSOF);
     }
 
     switch (memory[pc] & 0xff) {

test/test_errors.py

@@ -23,6 +23,16 @@
         "01 00  aa aa  3D 00  00 00",
         vmtest.EXIT_POB
     ),
+    Test(
+        "Return stack overflow",
+        "01 00  aa aa  0A 00  01 00  00 00  3D 00  00 00",
+        vmtest.EXIT_RSOF
+    ),
+    Test(
+        "Return stack underflow",
+        "0B 00  00 00",
+        vmtest.EXIT_RSUF
+    ),
 ]
 
 

test/vmtest.py

@@ -12,6 +12,10 @@
 EXIT_SUF = 5;
 EXIT_POB = 6;
 EXIT_OP = 7;
+EXIT_STR = 8;
+EXIT_ARGS = 9;
+EXIT_RSOF = 10;
+EXIT_RSUF = 11;
 
 ### Test Classes ###
 class VmTests(TestSuite):