From 47a4144b4756880356c09c59ba802daca6378777 Mon Sep 17 00:00:00 2001
From: Paul Fultz II <pfultz2@yahoo.com>
Date: Sun, 23 May 2021 03:20:29 -0500
Subject: [PATCH] Fix 10288: ValueFlow; False positives because of wrong known
 value when there is sign cast (#3268)

---
 lib/valueflow.cpp      |  7 ++++++-
 test/testvalueflow.cpp | 23 +++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 8d8c497f2..4668374fb 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -544,10 +544,15 @@ static void setTokenValue(Token* tok, const ValueFlow::Value &value, const Setti
 
     // cast..
     if (const Token *castType = getCastTypeStartToken(parent)) {
-        if (((tok->valueType() == nullptr && value.isImpossible()) || astIsPointer(tok)) && value.valueType == ValueFlow::Value::ValueType::INT &&
+        if (((tok->valueType() == nullptr && value.isImpossible()) || astIsPointer(tok)) &&
+            value.valueType == ValueFlow::Value::ValueType::INT &&
             Token::simpleMatch(parent->astOperand1(), "dynamic_cast"))
             return;
         const ValueType &valueType = ValueType::parseDecl(castType, settings);
+        if (value.isImpossible() && value.isIntValue() && value.intvalue < 0 && astIsUnsigned(tok) &&
+            valueType.sign == ValueType::SIGNED && tok->valueType() &&
+            ValueFlow::getSizeOf(*tok->valueType(), settings) >= ValueFlow::getSizeOf(valueType, settings))
+            return;
         setTokenValueCast(parent, valueType, value, settings);
     }
 
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index 61b397a71..c75a23bca 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -140,6 +140,7 @@ private:
 
         TEST_CASE(valueFlowUnknownMixedOperators);
         TEST_CASE(valueFlowIdempotent);
+        TEST_CASE(valueFlowUnsigned);
     }
 
     static bool isNotTokValue(const ValueFlow::Value &val) {
@@ -5607,6 +5608,28 @@ private:
                "}\n";
         ASSERT_EQUALS(false, testValueOfXKnown(code, 5U, 0));
     }
+
+    void valueFlowUnsigned() {
+        const char *code;
+
+        code = "auto f(uint32_t i) {\n"
+               "    auto x = i;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, -1));
+
+        code = "auto f(uint32_t i) {\n"
+               "    auto x = (int32_t)i;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(false, testValueOfXImpossible(code, 3U, -1));
+
+        code = "auto f(uint32_t i) {\n"
+               "    auto x = (int64_t)i;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, -1));
+    }
 };
 
 REGISTER_TEST(TestValueFlow)