Fixed #6317 (wrong simplification: int i = 1.5; return i; get simplified to: return 1.5;)

lib/valueflow.cpp

@@ -3564,6 +3564,30 @@ static void valueFlowForwardAssign(Token * const               tok,
     valueFlowForward(const_cast<Token *>(nextExpression), endOfVarScope, var, var->declarationId(), values, constValue, false, tokenlist, errorLogger, settings);
 }
 
+static std::list<ValueFlow::Value> truncateValues(std::list<ValueFlow::Value> values, const ValueType *valueType, const Settings *settings)
+{
+    if (!valueType || !valueType->isIntegral())
+        return values;
+
+    const size_t sz = getSizeOf(*valueType, settings);
+
+    for (ValueFlow::Value &value : values) {
+        if (value.isFloatValue()) {
+            value.intvalue = value.floatValue;
+            value.valueType = ValueFlow::Value::INT;
+        }
+
+        if (value.isIntValue() && sz > 0 && sz < 8) {
+            const MathLib::biguint unsignedMaxValue = (1ULL << (sz * 8)) - 1ULL;
+            const MathLib::biguint signBit = 1ULL << (sz * 8 - 1);
+            value.intvalue &= unsignedMaxValue;
+            if (valueType->sign == ValueType::Sign::SIGNED && (value.intvalue & signBit))
+                value.intvalue |= ~unsignedMaxValue;
+        }
+    }
+    return values;
+}
+
 static void valueFlowAfterAssign(TokenList *tokenlist, SymbolDatabase* symboldatabase, ErrorLogger *errorLogger, const Settings *settings)
 {
     for (const Scope * scope : symboldatabase->functionScopes) {
@@ -3593,7 +3617,7 @@ static void valueFlowAfterAssign(TokenList *tokenlist, SymbolDatabase* symboldat
             if (!tok->astOperand2() || tok->astOperand2()->values().empty())
                 continue;
 
-            std::list<ValueFlow::Value> values = tok->astOperand2()->values();
+            std::list<ValueFlow::Value> values = truncateValues(tok->astOperand2()->values(), tok->astOperand1()->valueType(), settings);
             const bool constValue = tok->astOperand2()->isNumber();
             const bool init = var->nameToken() == tok->astOperand1();
             valueFlowForwardAssign(const_cast<Token *>(tok->astOperand2()), var, values, constValue, init, tokenlist, errorLogger, settings);

test/testvalueflow.cpp

@@ -1443,6 +1443,25 @@ private:
                "}";
         ASSERT_EQUALS(false, testValueOfX(code, 4U, 0));
 
+        // truncation
+        code = "int f() {\n"
+               "  int x = 1.5;\n"
+               "  return x;\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, 1));
+
+        code = "int f() {\n"
+               "  unsigned char x = 0x123;\n"
+               "  return x;\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, 0x23));
+
+        code = "int f() {\n"
+               "  signed char x = 0xfe;\n"
+               "  return x;\n"
+               "}";
+        ASSERT_EQUALS(true, testValueOfX(code, 3U, -2));
+
         // function
         code = "void f() {\n"
                "    char *x = 0;\n"