01: Fixup & extend vm_regs example

Firstly, registers are set to fixed-width integers instead of
variable int. Secondly, a new instruction is added
(OP_JMP_REL_EQUAL), and lastly, the example program is updated.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

01/Makefile

@@ -3,4 +3,4 @@
 all: vm_regs
 
 %: %.c
-	$(CC) -std=c99 -ggdb -O0 -Wall -pedantic $< -o $@
+	$(CC) -std=c99 -ggdb -O0 -Wall -Werror=switch -Werror=switch-enum -pedantic $< -o $@

01/vm_regs.c

 #include <stdio.h>
+#include <inttypes.h>
 
 typedef enum {
     A = 0,
@@ -19,6 +20,7 @@ typedef enum {
     OP_JMP_REL,
     OP_JMP_REL_NEGATIVE,
     OP_JMP_REL_NOT_EQUAL,
+    OP_JMP_REL_EQUAL,
     OP_LOAD,
     OP_MOV,
     OP_XCHG,
@@ -28,7 +30,7 @@ typedef enum {
 } OpCode;
 
 static void
-set_flags(int value, int *flags_register)
+set_flags(int16_t value, uint8_t *flags_register)
 {
     int new_flags = 0;
 
@@ -41,90 +43,70 @@ set_flags(int value, int *flags_register)
 }
 
 int main() {
-    int program[] = {
-        OP_LOAD, A, 3,
-        OP_LOAD, B, 5,
-        OP_ADD, B,
-        OP_PRINT, A,
-        OP_LOAD, B, 1,
-        OP_ADD, B,
-        OP_PRINT, A,
-        OP_LOAD, A, 0,
+    int16_t program[] = {
+        OP_LOAD, A, 255,
         OP_LOAD, B, 0,
-        OP_PRINT, A,
-        OP_ADD_VALUE, 3,
-        OP_XCHG, A, B,
-        OP_ADD_VALUE, 1,
-        OP_TEST, 10,
-        OP_XCHG, A, B,
-        OP_JMP_REL_NOT_EQUAL, -16,
+        OP_ADD, B, A,
+        OP_ADD_VALUE, A, -1,
+        OP_TEST, A, 0,
+        OP_JMP_REL_NOT_EQUAL, -11,
+        OP_PRINT, B,
         OP_HALT
     };
 
-    int registers[4] = { 0 };
-    int flags_register = 0;
-    int *ip = program;
+    int16_t registers[4] = { 0 };
+    uint8_t flags_register = 0;
+    uint16_t *ip = (uint16_t *) program;
 
     while (1) {
         OpCode op = *ip++;
         switch (op) {
         case OP_LOAD: {
-            int idx = *ip++;
+            int16_t idx = *ip++;
             registers[idx] = *ip++;
             set_flags(registers[idx], &flags_register);
             break;
         }
         case OP_ADD: {
-            int val = registers[*ip++];
-            registers[A] += val;
-            set_flags(registers[A], &flags_register);
+            int16_t idx = *ip++;
+            int16_t val = registers[*ip++];
+            registers[idx] += val;
+            set_flags(registers[idx], &flags_register);
             break;
         }
         case OP_ADD_VALUE: {
-            int val = *ip++;
-            registers[A] += val;
+            /* TODO */
             break;
         }
         case OP_JMP_REL: {
-            int val = *ip++;
-            ip += val;
+            /* TODO */
             break;
         }
         case OP_NOP: {
             break;
         }
         case OP_TEST: {
-            int val = *ip++;
-            int new_val = val - registers[A];
-            set_flags(new_val, &flags_register);
+            /* TODO */
             break;
         }
         case OP_JMP_REL_NOT_EQUAL: {
-            int val = *ip++;
-            if (!(flags_register & FLAG_ZERO)) {
-                ip += val;
-            }
+            /* TODO */
             break;
         }
         case OP_JMP_REL_NEGATIVE: {
-            int val = *ip++;
-            if (!(flags_register & FLAG_NEGATIVE)) {
-                ip += val;
-            }
+            /* TODO */
+            break;
+        }
+        case OP_JMP_REL_EQUAL: {
+            /* TODO */
             break;
         }
         case OP_MOV: {
-            int dst = *ip++;
-            int src = *ip++;
-            registers[dst] = registers[src];
+            /* TODO */
             break;
         }
         case OP_XCHG: {
-            int r1 = *ip++;
-            int r2 = *ip++;
-            int tmp = registers[r1];
-            registers[r1] = registers[r2];
-            registers[r2] = tmp;
+            /* TODO */
             break;
         }
         case OP_PRINT:
@@ -133,7 +115,7 @@ int main() {
         case OP_HALT:
             return 0;
         default:
-            fprintf(stderr, "Unknown instruction %d\n", *ip);
+            fprintf(stderr, "Unknown instruction %" PRId16 "\n", *ip);
             return -1;
         }
     }