Switched the order of error checks to make the program out of bounds

error come before the stack overflow error. If the pc goes too far it
could trigger both and it is important to know that the pc went out of
bounds instead of seeing stack overflow in that case.

Author: strinsberg

main.c

@@ -16,28 +16,8 @@ const char* TEST_FILE = "test.vm";
   const bool DEBUGGING = false;
 #endif
 
-// TODO setup the program to take a filename as an argument
-// TODO setup an assembler (can use a different langauge).
-  
-// NOTE new OP codes must be added at the end of the enum. The testing program
-// will be broken if they are inserted in the middle.
-
-// NOTE Fixed point numbers are scaled by 1000 and only come signed
-// max number is MAX_INT / 1000 and smallest num is 0.001
-
-// NOTE PUSH, GET, CALL, and RET are all operations that must be given arguments
-// in the program because the nature of these instructions is that these values
-// will never be dynamic. If you want to push a value you will need to know
-// that value (if you know the address of that value it is a load now). GET you
-// need to have knowledge of the expected argument layout for the procedure you're
-// in. CALL you must know the label of the procedure when the program is written
-// or at least assembled. For CALL and RET it is necessary to know the number
-// of arguments that you will pass and return when calling or writing the
-// procedure.
-// All other instructions can operate on data they know nothing about so it must
-// be pushed or loaded onto the stack for them to get.
-
 // Macros //
+
 // NOTE these rely on the memory block being named mem and the stack pointer
 // being named sp. Also on the functions get/set_dword and get/set_qword and
 // the typedefs for signed types SWORD SDWORD SQWORD. All of these are
@@ -309,7 +289,15 @@ int main( int argc, char *argv[] ) {
 
   while (run) {
     /// Error Checking ///
-    if (sp > bp) {
+    if (pc >= prog_len) {
+      fprintf(stderr,
+              "Error: Program counter out of bounds: pc=0x%04x, prog_end=0x%04x\n",
+              pc, prog_len);
+      fprintf(stderr, "Stack: ");
+      display_range(mem, sp, bp);
+      fprintf(stderr, "\n");
+      exit(EXIT_POB);
+    } else if (sp > bp) {
       fprintf(stderr, "Error: Stack Underflow: sp=0x%04x, bp=0x%04x\n", sp, bp);
       fprintf(stderr, "Stack: ");
       display_range(mem, sp, bp);
@@ -319,14 +307,6 @@ int main( int argc, char *argv[] ) {
       fprintf(stderr, "Error: Stack Overflow: sp=0x%04x, brk=0x%04x, prg=0x%04x\n",
               sp, brk, prog_len);
       exit(EXIT_SOF);
-    } else if (pc >= prog_len) {
-      fprintf(stderr,
-              "Error: Program counter out of bounds: pc=0x%04x, prog_end=0x%04x\n",
-              pc, prog_len);
-      fprintf(stderr, "Stack: ");
-      display_range(mem, sp, bp);
-      fprintf(stderr, "\n");
-      exit(EXIT_POB);
     }
 
     if (DEBUGGING) {