Update can_helpers to remove UB

Author: Wetmelon

src/can_helpers.hpp

@@ -1,52 +1,43 @@
 #pragma once
 
-#include <string.h>
 #include <stdint.h>
+#include <string.h>
 
-template <typename T>
+
+template<typename T>
 T can_get_signal_raw(const uint8_t* buf, const size_t startBit, const size_t length, const bool isIntel) {
     constexpr int N = 8;
 
-    union {
-        uint64_t tempVal;
-        uint8_t tempBuf[N]; // This is used because memcpy into tempVal generates less optimal code
-        T retVal;
-    };
-
     const uint64_t mask = length < 64 ? (1ULL << length) - 1ULL : -1ULL;
     const uint8_t shift = isIntel ? startBit : (64 - startBit) - length;
 
-    memcpy(tempBuf, buf, N);
+    uint64_t tempVal = 0;
+    memcpy(&tempVal, buf, N);
     if (isIntel) {
         tempVal = (tempVal >> shift) & mask;
     } else {
         tempVal = __builtin_bswap64(tempVal);
         tempVal = (tempVal >> shift) & mask;
     }
 
+    T retVal;
+    memcpy(&retVal, &tempVal, sizeof(T));
+
     return retVal;
 }
 
-template <typename T>
+template<typename T>
 void can_set_signal_raw(uint8_t* buf, const T val, const size_t startBit, const size_t length, const bool isIntel) {
     constexpr int N = 8;
 
     const uint64_t mask = length < 64 ? (1ULL << length) - 1ULL : -1ULL;
     const uint8_t shift = isIntel ? startBit : (64 - startBit) - length;
 
-    union {
-        uint64_t valAsBits;
-        T tempVal;
-    };
-
-    tempVal = val;
-
-    union {
-        uint64_t data;
-        uint8_t tempBuf[N];
-    };
+    uint64_t valAsBits = 0;
+    memcpy(&valAsBits, &val, sizeof(T));
 
-    memcpy(tempBuf, buf, N);
+    uint64_t data = 0;
+    memcpy(&data, buf, N);
     if (isIntel) {
         data &= ~(mask << shift);
         data |= valAsBits << shift;
@@ -57,10 +48,10 @@ void can_set_signal_raw(uint8_t* buf, const T val, const size_t startBit, const
         data = __builtin_bswap64(data);
     }
 
-    memcpy(buf, tempBuf, N);
+    memcpy(buf, &data, N);
 }
 
-template <typename T>
+template<typename T>
 float can_get_signal_raw(
     const uint8_t* buf,
     const size_t startBit,
@@ -73,7 +64,7 @@ float can_get_signal_raw(
     return (retVal * factor) + offset;
 }
 
-template <typename T>
+template<typename T>
 constexpr void can_set_signal_raw(
     uint8_t* buf,
     const float val,
@@ -87,12 +78,12 @@ constexpr void can_set_signal_raw(
     can_set_signal_raw<T>(buf, scaledVal, startBit, length, isIntel);
 }
 
-template <typename T, typename TMsg>
+template<typename T, typename TMsg>
 constexpr T can_get_signal(const TMsg& msg, const size_t startBit, const size_t length, const bool isIntel) {
     return can_get_signal_raw<T>(can_msg_get_payload(msg).data(), startBit, length, isIntel);
 }
 
-template <typename T, typename TMsg>
+template<typename T, typename TMsg>
 constexpr void can_set_signal(TMsg& msg, const T val, const size_t startBit, const size_t length, const bool isIntel) {
     can_set_signal_raw<T>(can_msg_get_payload(msg).data(), val, startBit, length, isIntel);
 }