change + to wrapping_add

This gets the tests to pass again. Without this, execution stops at an
overflow.

tests/symbolic/manticore.rs

@@ -13,7 +13,7 @@ fn check_char_0(mut ch: u8) -> Result<(), ()> {
 
 fn check_char_1(mut ch: u8) -> Result<(), ()> {
     ch ^= 107;
-    ch += 67;
+    ch = ch.wrapping_add(67);
 
     if ch == 105 {
         Ok(())
@@ -23,7 +23,7 @@ fn check_char_1(mut ch: u8) -> Result<(), ()> {
 }
 
 fn check_char_2(mut ch: u8) -> Result<(), ()> {
-    ch += 61;
+    ch = ch.wrapping_add(61);
     ch *= 2;
 
     if ch == 252 {
@@ -66,7 +66,7 @@ fn check_char_5(mut ch: u8) -> Result<(), ()> {
 }
 
 fn check_char_6(mut ch: u8) -> Result<(), ()> {
-    ch += 71;
+    ch = ch.wrapping_add(71);
 
     if ch == 138 {
         Ok(())
@@ -86,8 +86,8 @@ fn check_char_7(mut ch: u8) -> Result<(), ()> {
 }
 
 fn check_char_8(mut ch: u8) -> Result<(), ()> {
-    ch += 41;
-    ch += 53;
+    ch = ch.wrapping_add(41);
+    ch = ch.wrapping_add(53);
 
     if ch == 176 {
         Ok(())
@@ -98,8 +98,8 @@ fn check_char_8(mut ch: u8) -> Result<(), ()> {
 
 fn check_char_9(mut ch: u8) -> Result<(), ()> {
     ch ^= 61;
-    ch += 41;
-    ch += 11;
+    ch = ch.wrapping_add(41);
+    ch = ch.wrapping_add(11);
 
     if ch == 172 {
         Ok(())
@@ -110,8 +110,8 @@ fn check_char_9(mut ch: u8) -> Result<(), ()> {
 
 fn check_char_10(mut ch: u8) -> Result<(), ()> {
     ch ^= 47;
-    ch += 29;
-    ch += 67;
+    ch = ch.wrapping_add(29);
+    ch = ch.wrapping_add(67);
 
     if ch == 114 {
         Ok(())

tests/symbolic/ptr_offset.rs

@@ -11,7 +11,7 @@ fn main() {
     let d0 = data[0]; // 2
     let d1 = data[1]; // 4
 
-    if (d0 + d1) as usize >= v.len() {
+    if (d0.wrapping_add(d1)) as usize >= v.len() {
         return;
     }
 

tests/symbolic/write_mem.rs

@@ -10,11 +10,11 @@ fn main() {
     // should panic on [ 7, 3, 21, 21 ]
 
     if data.len() >= 4 {
-        let mut v = [0; BUFFER_LENGTH];
-        v[0] += data[3];
-        v[1] = v[0] + data[2];
+        let mut v: [u8; BUFFER_LENGTH] = [0; BUFFER_LENGTH];
+        v[0] = v[0].wrapping_add(data[3]);
+        v[1] = v[0].wrapping_add(data[2]);
         if v[0] == 21 && v[1] == 42 {
-            v[0] = data[0] + data[1];
+            v[0] = data[0].wrapping_add(data[1]);
             v[3] = data[0];
             if v[3] == 7 && v[0] == 10 {
                 panic!()