Fix 12032: False positive: uninitialized variable, flags with same value (#5754)

Author: pfultz2

lib/programmemory.cpp

@@ -1640,6 +1640,14 @@ namespace {
             return *it;
         }
 
+        static bool updateValue(ValueFlow::Value& v, ValueFlow::Value x)
+        {
+            const bool returnValue = !x.isUninitValue() && !x.isImpossible();
+            if (v.isUninitValue() || returnValue)
+                v = std::move(x);
+            return returnValue;
+        }
+
         ValueFlow::Value execute(const Token* expr)
         {
             depth--;
@@ -1648,13 +1656,29 @@ namespace {
                 }};
             if (depth < 0)
                 return unknown();
-            ValueFlow::Value v = executeImpl(expr);
-            if (!v.isUninitValue())
+            ValueFlow::Value v = unknown();
+            if (updateValue(v, executeImpl(expr)))
                 return v;
             if (!expr)
                 return v;
-            if (expr->exprId() > 0 && pm->hasValue(expr->exprId()))
-                return pm->at(expr->exprId());
+            if (expr->exprId() > 0 && pm->hasValue(expr->exprId())) {
+                if (updateValue(v, pm->at(expr->exprId())))
+                    return v;
+            }
+            // Find symbolic values
+            for (const ValueFlow::Value& value : expr->values()) {
+                if (!value.isSymbolicValue())
+                    continue;
+                if (!value.isKnown())
+                    continue;
+                if (value.tokvalue->exprId() > 0 && !pm->hasValue(value.tokvalue->exprId()))
+                    continue;
+                ValueFlow::Value v2 = pm->at(value.tokvalue->exprId());
+                if (!v2.isIntValue() && value.intvalue != 0)
+                    continue;
+                v2.intvalue += value.intvalue;
+                return v2;
+            }
             if (const ValueFlow::Value* value = getImpossibleValue(expr))
                 return *value;
             return v;

test/testvalueflow.cpp

@@ -5645,6 +5645,22 @@ class TestValueFlow : public TestFixture {
         values = tokenValues(code, "x <", ValueFlow::Value::ValueType::UNINIT);
         ASSERT_EQUALS(0, values.size());
 
+        code = "void getX(int *p);\n"
+               "bool do_something();\n"
+               "void foo() {\n"
+               "  int x;\n"
+               "  bool flag;\n"
+               "  bool success;\n"
+               "  success = do_something();\n"
+               "  flag = success;\n"
+               "  if (success == true) {\n"
+               "    getX(&x);\n"
+               "  }\n"
+               "  for (int i = 0; (flag == true) && (i < x); ++i) {}\n"
+               "}\n";
+        values = tokenValues(code, "x ) ; ++ i", ValueFlow::Value::ValueType::UNINIT);
+        ASSERT_EQUALS(0, values.size());
+
         code = "void g(bool *result, size_t *buflen) {\n" // #12091
                "    if (*result && *buflen >= 5) {}\n" // <- *buflen might not be initialized
                "}\n"