diff --git a/cpu.c b/cpu.c
index 535907f..5ad1161 100644
--- a/cpu.c
+++ b/cpu.c
@@ -50,7 +50,7 @@ void teq(uint16_t dst, uint16_t a, uint16_t b)
     {
         b = regs[b % (MAX_INT+1)];
     }
-    regs[dst % (MAX_INT+1)] = (a == b);
+    regs[dst % (MAX_INT+1)] = (uint16_t)(a == b);
 }
 
 void tgt(uint16_t dst, uint16_t a, uint16_t b)
@@ -63,7 +63,7 @@ void tgt(uint16_t dst, uint16_t a, uint16_t b)
     {
         b = regs[b % (MAX_INT+1)];
     }
-    regs[dst % (MAX_INT+1)] = (a > b);
+    regs[dst % (MAX_INT+1)] = (uint16_t)(a > b);
 }
 
 void jmp(uint16_t dst)
@@ -112,7 +112,7 @@ void add(uint16_t dst, uint16_t a, uint16_t b)
     {
         b = regs[b % (MAX_INT+1)];
     }
-    regs[dst % (MAX_INT+1)] = (a + b) % (MAX_INT+1);
+    regs[dst % (MAX_INT+1)] = (uint16_t)((a + b) % (MAX_INT+1));
 }
 
 void mul(uint16_t dst, uint16_t a, uint16_t b)
@@ -125,7 +125,7 @@ void mul(uint16_t dst, uint16_t a, uint16_t b)
     {
         b = regs[b % (MAX_INT+1)];
     }
-    regs[dst % (MAX_INT+1)] = (a * b) % (MAX_INT+1);
+    regs[dst % (MAX_INT+1)] = (uint16_t)((a * b) % (MAX_INT+1));
 }
 
 void mod(uint16_t dst, uint16_t a, uint16_t b)
@@ -173,7 +173,7 @@ void not(uint16_t dst, uint16_t src)
     {
         src = regs[src % (MAX_INT+1)];
     }
-    regs[dst % (MAX_INT+1)] = ~src & 0x7FFF;
+    regs[dst % (MAX_INT+1)] = (uint16_t)(~src & 0x7FFF);
 }
 
 void load(uint16_t dst, uint16_t src)
diff --git a/debug.c b/debug.c
index ee9a64d..a1d7aa7 100644
--- a/debug.c
+++ b/debug.c
@@ -30,7 +30,8 @@ void load_state(char *filename)
     uint16_t regsdump[NUM_REGISTERS+1];
     uint16_t memdump[MEMSIZE];
     uint16_t *stackdump;
-    uint32_t stacksize, stackpos;
+    uint32_t stacksize;
+    long stackpos;
     
     fread(regsdump,sizeof(uint16_t),NUM_REGISTERS+1,state);
     fread(memdump,sizeof(uint16_t),MEMSIZE,state);
@@ -99,7 +100,7 @@ void query()
                 sscanf(input,"b %hu\n",&bpoint);
                 fprintf(stderr,"Set breakpoint %hu to %hu",nbpoints,bpoint);
                 breakpoints[nbpoints] = bpoint;
-                nbpoints = nbpoints + 1 % 0xFF;
+                nbpoints = (uint16_t)(nbpoints + 1 % 0xFF);
                 break;
             case 'd':
                 sscanf(input,"d %hu\n",&bpoint);
diff --git a/main.c b/main.c
index b9fd14b..21f9876 100644
--- a/main.c
+++ b/main.c
@@ -4,7 +4,6 @@
 #include "mem.h"
 #include "stack.h"
 #include "disasm.h"
-#include "debug.h"
 
 uint32_t load_program(const char* path)
 {
@@ -14,7 +13,7 @@ uint32_t load_program(const char* path)
     rewind(fp);
     fread(mem,1,(size_t)file_size,fp);
     fclose(fp);
-    return file_size/2;
+    return (uint32_t)file_size/2;
 }
 
 void initializevm(char *program)
@@ -51,8 +50,8 @@ int main(int argc, char** argv)
     uint8_t disasm_flag = 0;
     uint8_t err = 0;
     char c;
-    char *program;
-    while ((c = getopt(argc, argv, "s:d:")) != -1)
+    char *program = NULL;
+    while ((c = (char)getopt(argc, argv, "s:d:")) != -1)
     {
         switch(c)
         {
@@ -65,6 +64,7 @@ int main(int argc, char** argv)
                 program = optarg;
                 break;
             case '?':
+            default:
                 err = 1;
                 break;
         }
diff --git a/stack.c b/stack.c
index 1c62189..776c07f 100644
--- a/stack.c
+++ b/stack.c
@@ -9,7 +9,7 @@
 
 uint8_t STACK_FAULT = 0;
 uint32_t stack_size = EXTEND_SIZE;
-uint32_t stack_pos = -1;
+uint32_t stack_pos = 0xFFFF;
 uint32_t stack_elems = 0;
 uint16_t *stack;
 
@@ -64,7 +64,7 @@ uint16_t stack_pop()
     if(!stack_elems)
     {
         STACK_FAULT = 1;
-        return -1;
+        return 0xFFFF;
     }
     uint16_t value = stack[stack_pos--];
     if(stack_size - --stack_elems == 2*EXTEND_SIZE)