account for ordering of options when computing FileSettings::hash

Author: ludviggunne

lib/filesettings.h

@@ -96,17 +96,25 @@ struct CPPCHECKLIB FileSettings {
 
         hash ^= std::hash<std::string>{}(standard);
 
-        for (const auto &undef : undefs)
+        for (const auto &undef : undefs) {
+            hash = rotateLeft(hash, 1);
             hash ^= std::hash<std::string>{}(undef);
+        }
 
-        for (const auto &includePath : includePaths)
+        for (const auto &includePath : includePaths) {
+            hash = rotateLeft(hash, 1);
             hash ^= std::hash<std::string>{}(includePath);
+        }
 
-        for (const auto &systemIncludePath : systemIncludePaths)
+        for (const auto &systemIncludePath : systemIncludePaths) {
+            hash = rotateLeft(hash, 1);
             hash ^= std::hash<std::string>{}(systemIncludePath);
+        }
 
-        for (const auto &define : splitString(defines, ';'))
+        for (const auto &define : splitString(defines, ';')) {
+            hash = rotateLeft(hash, 1);
             hash ^= std::hash<std::string>{}(define);
+        }
     }
 
     std::string cfg;

lib/utils.h

@@ -397,6 +397,12 @@ static inline T* empty_if_null(T* p)
     return default_if_null(p, "");
 }
 
+template<typename T>
+static inline T rotateLeft(T value, std::size_t amount)
+{
+    return (value << amount) | (value >> (8 * sizeof(T) - amount));
+}
+
 /**
  * Split string by given sperator.
  * @param str The string to split

test/testutils.cpp

@@ -44,6 +44,7 @@ class TestUtils : public TestFixture {
         TEST_CASE(splitString);
         TEST_CASE(as_const);
         TEST_CASE(memoize);
+        TEST_CASE(rotateLeft);
     }
 
     void isValidGlobPattern() const {
@@ -535,6 +536,14 @@ class TestUtils : public TestFixture {
         ASSERT_EQUALS(1, callF());
         ASSERT_EQUALS(1, count);
     }
+
+    void rotateLeft() const {
+        uint8_t value_u8 = 0b01010101;
+        ASSERT_EQUALS(::rotateLeft(value_u8, 1), 0b10101010);
+
+        uint64_t value_u64 = 0xABCDEF0123456789;
+        ASSERT_EQUALS(::rotateLeft(value_u64, 8), 0xCDEF0123456789AB);
+    }
 };
 
 REGISTER_TEST(TestUtils)