Fixed #10499 (FP: misra-c2012-10.4)

Author: danmar

addons/misra.py

@@ -459,6 +459,13 @@ def getEssentialTypeCategory(expr):
                 if typeToken.valueType.sign:
                     return typeToken.valueType.sign
             typeToken = typeToken.next
+
+    # See Appendix D, section D.6, Character constants
+    if expr.str[0] == "'" and expr.str[-1] == "'":
+        if len(expr.str) == 3 or (len(expr.str) == 4 and expr.str[1] == '\\'):
+            return 'char'
+        return expr.valueType.sign
+
     if expr.valueType:
         return expr.valueType.sign
     return None

addons/test/misra/misra-test.c

@@ -669,13 +669,13 @@ static void misra_10_2(void) {
     float f32a = 0.0;
     char res;
 
-    res = '0' + u8a; // 10.4
+    res = '0' + u8a; // Convert u8a to digit
     res = s8a + '0';
     res = cha - '0';
     res = '0' - s8a;
     res = cha + ':'; // 10.2
 
-    res = s16a - 'a'; // 10.2 10.3
+    res = s16a - 'a'; // 10.2 10.3 10.4
     res = '0' + f32a; // 10.2 10.4
 }
 
@@ -699,6 +699,12 @@ static void misra_10_4(u32 x, s32 y) {
   z = x + y; //10.4
   z = (a == misra_10_4_A3) ? x : y; //10.4
   z = (a == misra_10_4_A3) ? y : y; // no-warning
+  
+  // #10499
+  const char buf[10] = {0};
+  if ('0' == buf[x]) // no-warning
+  {
+  }
 }
 
 static void misra_10_5(uint16_t x) {