diff --git a/board/drivers/gmlan_alt.h b/board/drivers/gmlan_alt.h
index c8d7f0da275303..c3d5d304e63c48 100644
--- a/board/drivers/gmlan_alt.h
+++ b/board/drivers/gmlan_alt.h
@@ -49,27 +49,30 @@ int append_crc(char *in, int in_len) {
     }
     crc &= 0x7fffU;
   }
+  int in_len_copy = in_len;
   for (int i = 14; i >= 0; i--) {
-    in[in_len] = (crc >> (unsigned int)(i)) & 1U;
-    in_len++;
+    in[in_len_copy] = (crc >> (unsigned int)(i)) & 1U;
+    in_len_copy++;
   }
-  return in_len;
+  return in_len_copy;
 }
 
 int append_bits(char *in, int in_len, char *app, int app_len) {
+  int in_len_copy = in_len;
   for (int i = 0; i < app_len; i++) {
-    in[in_len] = app[i];
-    in_len++;
+    in[in_len_copy] = app[i];
+    in_len_copy++;
   }
-  return in_len;
+  return in_len_copy;
 }
 
 int append_int(char *in, int in_len, int val, int val_len) {
+  int in_len_copy = in_len;
   for (int i = val_len-1; i >= 0; i--) {
-    in[in_len] = ((unsigned int)(val) & (1U << (unsigned int)(i))) != 0;
-    in_len++;
+    in[in_len_copy] = ((unsigned int)(val) & (1U << (unsigned int)(i))) != 0;
+    in_len_copy++;
   }
-  return in_len;
+  return in_len_copy;
 }
 
 int get_bit_message(char *out, CAN_FIFOMailBox_TypeDef *to_bang) {
diff --git a/board/drivers/uart.h b/board/drivers/uart.h
index 65e7fdd3cf16bf..56453715aa701c 100644
--- a/board/drivers/uart.h
+++ b/board/drivers/uart.h
@@ -307,22 +307,23 @@ void putch(const char a) {
 }
 
 void puts(const char *a) {
-  for (;*a;a++) {
-    if (*a == '\n') putch('\r');
-    putch(*a);
+  for (const char *in = a; *in; in++) {
+    if (*in == '\n') putch('\r');
+    putch(*in);
   }
 }
 
 void putui(uint32_t i) {
+  uint32_t i_copy = i;
   char str[11];
   uint8_t idx = 10;
   str[idx] = '\0';
   idx--;
   do {
-    str[idx] = (i % 10) + 0x30;
+    str[idx] = (i_copy % 10) + 0x30;
     idx--;
-    i /= 10;
-  } while (i != 0);
+    i_copy /= 10;
+  } while (i_copy != 0);
   puts(str + idx + 1);
 }