Add symbolic values to ValueFlow (#3367)

lib/astutils.cpp

@@ -878,7 +878,7 @@ static bool compareKnownValue(const Token * const tok1, const Token * const tok2
     if (v1 == tok1->values().end()) {
         return false;
     }
-    if (v1->isNonValue() || v1->isContainerSizeValue())
+    if (v1->isNonValue() || v1->isContainerSizeValue() || v1->isSymbolicValue())
         return false;
     const auto v2 = std::find_if(tok2->values().begin(), tok2->values().end(), isKnownFn);
     if (v2 == tok2->values().end()) {

lib/reverseanalyzer.cpp

@@ -172,7 +172,7 @@ struct ReverseTraversal {
                                                     settings);
                         }
                         // Assignment to
-                    } else if (lhsAction.matches() && !assignTok->astOperand2()->hasKnownValue() &&
+                    } else if (lhsAction.matches() && !assignTok->astOperand2()->hasKnownIntValue() &&
                                isConstExpression(assignTok->astOperand2(), settings->library, true, true)) {
                         const std::string info = "Assignment to '" + assignTok->expressionString() + "'";
                         ValuePtr<Analyzer> a = analyzer->reanalyze(assignTok->astOperand2(), info);

lib/token.cpp

@@ -1292,7 +1292,6 @@ std::string Token::stringifyList(const stringifyOptions& options, const std::vec
                 if (options.linenumbers) {
                     ret += std::to_string(lineNumber);
                     ret += ':';
-                    if (lineNumber == tok->linenr())
                     ret += ' ';
                 }
             } else {
@@ -1742,6 +1741,10 @@ void Token::printValueFlow(bool xml, std::ostream &out) const
                 case ValueFlow::Value::ValueType::LIFETIME:
                     out << "lifetime=\"" << value.tokvalue << '\"';
                     break;
+                case ValueFlow::Value::ValueType::SYMBOLIC:
+                    out << "tokvalue=\"" << value.tokvalue << '\"';
+                    out << " intvalue=\"" << value.intvalue << '\"';
+                    break;
                 }
                 if (value.condition)
                     out << " condition-line=\"" << value.condition->linenr() << '\"';
@@ -1795,6 +1798,14 @@ void Token::printValueFlow(bool xml, std::ostream &out) const
                     out << "lifetime[" << ValueFlow::Value::toString(value.lifetimeKind) << "]=("
                         << value.tokvalue->expressionString() << ")";
                     break;
+                case ValueFlow::Value::ValueType::SYMBOLIC:
+                    out << "symbolic=(" << value.tokvalue->expressionString();
+                    if (value.intvalue > 0)
+                        out << "+" << value.intvalue;
+                    else if (value.intvalue < 0)
+                        out << "-" << -value.intvalue;
+                    out << ")";
+                    break;
                 }
                 if (value.indirect > 0)
                     for (int i=0; i<value.indirect; i++)
@@ -2124,8 +2135,13 @@ bool Token::addValue(const ValueFlow::Value &value)
 {
     if (value.isKnown() && mImpl->mValues) {
         // Clear all other values of the same type since value is known
-        mImpl->mValues->remove_if([&](const ValueFlow::Value & x) {
+        mImpl->mValues->remove_if([&](const ValueFlow::Value& x) {
-            return x.valueType == value.valueType;
+            if (x.valueType != value.valueType)
+                return false;
+            // Allow multiple known symbolic values
+            if (x.isSymbolicValue())
+                return !x.isKnown();
+            return true;
         });
     }
 
@@ -2146,31 +2162,7 @@ bool Token::addValue(const ValueFlow::Value &value)
                 continue;
 
             // different value => continue
-            bool differentValue = true;
+            if (!it->equalValue(value))
-            switch (it->valueType) {
-            case ValueFlow::Value::ValueType::INT:
-            case ValueFlow::Value::ValueType::CONTAINER_SIZE:
-            case ValueFlow::Value::ValueType::BUFFER_SIZE:
-            case ValueFlow::Value::ValueType::ITERATOR_START:
-            case ValueFlow::Value::ValueType::ITERATOR_END:
-                differentValue = (it->intvalue != value.intvalue);
-                break;
-            case ValueFlow::Value::ValueType::TOK:
-            case ValueFlow::Value::ValueType::LIFETIME:
-                differentValue = (it->tokvalue != value.tokvalue);
-                break;
-            case ValueFlow::Value::ValueType::FLOAT:
-                // TODO: Write some better comparison
-                differentValue = (it->floatValue > value.floatValue || it->floatValue < value.floatValue);
-                break;
-            case ValueFlow::Value::ValueType::MOVED:
-                differentValue = (it->moveKind != value.moveKind);
-                break;
-            case ValueFlow::Value::ValueType::UNINIT:
-                differentValue = false;
-                break;
-            }
-            if (differentValue)
                 continue;
 
             if ((value.isTokValue() || value.isLifetimeValue()) && (it->tokvalue != value.tokvalue) && (it->tokvalue->str() != value.tokvalue->str()))

lib/valueflow.cpp

@@ -1387,7 +1387,7 @@ static void valueFlowBitAnd(TokenList *tokenlist)
 static void valueFlowSameExpressions(TokenList *tokenlist)
 {
     for (Token *tok = tokenlist->front(); tok; tok = tok->next()) {
-        if (tok->hasKnownValue())
+        if (tok->hasKnownIntValue())
             continue;
 
         if (!tok->astOperand1() || !tok->astOperand2())
@@ -2032,7 +2032,7 @@ struct ValueFlowAnalyzer : Analyzer {
         const ValueFlow::Value* value = getValue(tok);
         if (!value)
             return Action::None;
-        if (!(value->isIntValue() || value->isFloatValue()))
+        if (!(value->isIntValue() || value->isFloatValue() || value->isSymbolicValue()))
             return Action::None;
         const Token* parent = tok->astParent();
 
@@ -2409,6 +2409,8 @@ struct ExpressionAnalyzer : SingleValueFlowAnalyzer {
 
         dependOnThis = exprDependsOnThis(expr);
         setupExprVarIds(expr);
+        if (val.isSymbolicValue())
+            setupExprVarIds(val.tokvalue);
     }
 
     virtual const ValueType* getValueType(const Token*) const OVERRIDE {
@@ -3992,6 +3994,100 @@ static void valueFlowConditionExpressions(TokenList *tokenlist, SymbolDatabase*
     }
 }
 
+static ValueFlow::Value makeSymbolic(const Token* tok, MathLib::bigint delta = 0)
+{
+    ValueFlow::Value value;
+    value.setKnown();
+    value.valueType = ValueFlow::Value::ValueType::SYMBOLIC;
+    value.tokvalue = tok;
+    value.intvalue = delta;
+    return value;
+}
+
+static void valueFlowSymbolic(TokenList* tokenlist, SymbolDatabase* symboldatabase)
+{
+    for (const Scope* scope : symboldatabase->functionScopes) {
+        for (Token* tok = const_cast<Token*>(scope->bodyStart); tok != scope->bodyEnd; tok = tok->next()) {
+            if (!Token::simpleMatch(tok, "="))
+                continue;
+            if (!tok->astOperand1())
+                continue;
+            if (!tok->astOperand2())
+                continue;
+            if (tok->astOperand1()->hasKnownIntValue())
+                continue;
+            if (tok->astOperand2()->hasKnownIntValue())
+                continue;
+
+            Token* start = nextAfterAstRightmostLeaf(tok);
+            const Token* end = scope->bodyEnd;
+
+            ValueFlow::Value rhs = makeSymbolic(tok->astOperand2());
+            rhs.errorPath.emplace_back(tok,
+                                       tok->astOperand1()->expressionString() + " is assigned '" +
+                                           tok->astOperand2()->expressionString() + "' here.");
+            valueFlowForward(start, end, tok->astOperand1(), {rhs}, tokenlist, tokenlist->getSettings());
+
+            ValueFlow::Value lhs = makeSymbolic(tok->astOperand1());
+            lhs.errorPath.emplace_back(tok,
+                                       tok->astOperand1()->expressionString() + " is assigned '" +
+                                           tok->astOperand2()->expressionString() + "' here.");
+            valueFlowForward(start, end, tok->astOperand2(), {lhs}, tokenlist, tokenlist->getSettings());
+        }
+    }
+}
+
+static void valueFlowSymbolicInfer(TokenList* tokenlist, SymbolDatabase* symboldatabase)
+{
+    for (const Scope* scope : symboldatabase->functionScopes) {
+        for (Token* tok = const_cast<Token*>(scope->bodyStart); tok != scope->bodyEnd; tok = tok->next()) {
+            if (!Token::Match(tok, "-|%comp%"))
+                continue;
+            if (tok->hasKnownIntValue())
+                continue;
+            if (!tok->astOperand1())
+                continue;
+            if (!tok->astOperand2())
+                continue;
+            if (tok->astOperand1()->hasKnownIntValue())
+                continue;
+            if (tok->astOperand2()->hasKnownIntValue())
+                continue;
+
+            MathLib::bigint rhsvalue = 0;
+            const ValueFlow::Value* rhs =
+                ValueFlow::findValue(tok->astOperand2()->values(), nullptr, [&](const ValueFlow::Value& v) {
+                    return v.isSymbolicValue() && v.tokvalue && v.tokvalue->exprId() == tok->astOperand1()->exprId();
+                });
+            if (rhs)
+                rhsvalue = rhs->intvalue;
+            MathLib::bigint lhsvalue = 0;
+            const ValueFlow::Value* lhs =
+                ValueFlow::findValue(tok->astOperand1()->values(), nullptr, [&](const ValueFlow::Value& v) {
+                    return v.isSymbolicValue() && v.tokvalue && v.tokvalue->exprId() == tok->astOperand2()->exprId();
+                });
+            if (lhs)
+                lhsvalue = lhs->intvalue;
+            if (!lhs && !rhs)
+                continue;
+
+            ValueFlow::Value value{calculate(tok->str(), lhsvalue, rhsvalue)};
+            if (lhs && rhs) {
+                if (lhs->isImpossible() != rhs->isImpossible())
+                    continue;
+                combineValueProperties(*lhs, *rhs, &value);
+            } else if (lhs) {
+                value.valueKind = lhs->valueKind;
+                value.errorPath = lhs->errorPath;
+            } else if (rhs) {
+                value.valueKind = rhs->valueKind;
+                value.errorPath = rhs->errorPath;
+            }
+            setTokenValue(tok, value, tokenlist->getSettings());
+        }
+    }
+}
+
 static void valueFlowForwardAssign(Token* const tok,
                                    const Token* expr,
                                    std::vector<const Variable*> vars,
@@ -4044,17 +4140,13 @@ static void valueFlowForwardAssign(Token* const tok,
     // Skip RHS
     const Token * nextExpression = tok->astParent() ? nextAfterAstRightmostLeaf(tok->astParent()) : tok->next();
 
-    if (std::any_of(values.begin(), values.end(), std::mem_fn(&ValueFlow::Value::isTokValue))) {
+    for (ValueFlow::Value& value : values) {
-        std::list<ValueFlow::Value> tokvalues;
+        if (value.isSymbolicValue())
-        std::copy_if(values.begin(),
+            continue;
-                     values.end(),
+        if (value.isTokValue())
-                     std::back_inserter(tokvalues),
+            continue;
-                     std::mem_fn(&ValueFlow::Value::isTokValue));
-        valueFlowForward(const_cast<Token*>(nextExpression), endOfVarScope, expr, values, tokenlist, settings);
-        values.remove_if(std::mem_fn(&ValueFlow::Value::isTokValue));
-    }
-    for (ValueFlow::Value& value:values)
         value.tokvalue = tok;
+    }
     valueFlowForward(const_cast<Token*>(nextExpression), endOfVarScope, expr, values, tokenlist, settings);
 }
 
@@ -4163,7 +4255,7 @@ static void valueFlowAfterAssign(TokenList *tokenlist, SymbolDatabase* symboldat
             std::set<ValueFlow::Value::ValueType> types;
             if (tok->astOperand1()->hasKnownValue()) {
                 for (const ValueFlow::Value& value:tok->astOperand1()->values()) {
-                    if (value.isKnown())
+                    if (value.isKnown() && !value.isSymbolicValue())
                         types.insert(value.valueType);
                 }
             }
@@ -4719,7 +4811,7 @@ struct SimpleConditionHandler : ConditionHandler {
         ValueFlow::Value false_value;
         const Token *vartok = parseCompareInt(tok, true_value, false_value);
         if (vartok) {
-            if (vartok->hasKnownValue())
+            if (vartok->hasKnownIntValue())
                 return {};
             if (vartok->str() == "=" && vartok->astOperand1() && vartok->astOperand2())
                 vartok = vartok->astOperand1();
@@ -4887,7 +4979,7 @@ static void valueFlowInferCondition(TokenList* tokenlist,
     for (Token* tok = tokenlist->front(); tok; tok = tok->next()) {
         if (!tok->astParent())
             continue;
-        if (tok->hasKnownValue())
+        if (tok->hasKnownIntValue())
             continue;
         if (tok->variable() && (Token::Match(tok->astParent(), "?|&&|!|%oror%") ||
                                 Token::Match(tok->astParent()->previous(), "if|while ("))) {
@@ -6365,7 +6457,7 @@ static void valueFlowContainerSize(TokenList *tokenlist, SymbolDatabase* symbold
             continue;
         if (!astIsContainer(var->nameToken()))
             continue;
-        if (var->nameToken()->hasKnownValue())
+        if (var->nameToken()->hasKnownValue(ValueFlow::Value::ValueType::CONTAINER_SIZE))
             continue;
         if (!Token::Match(var->nameToken(), "%name% ;") &&
             !(Token::Match(var->nameToken(), "%name% {") && Token::simpleMatch(var->nameToken()->next()->link(), "} ;")))
@@ -6824,6 +6916,13 @@ std::string ValueFlow::Value::infoString() const
         return "end=" + MathLib::toString(intvalue);
     case ValueType::LIFETIME:
         return "lifetime=" + tokvalue->str();
+    case ValueType::SYMBOLIC:
+        std::string result = "symbolic=" + tokvalue->expressionString();
+        if (intvalue > 0)
+            result += "+" + MathLib::toString(intvalue);
+        else if (intvalue < 0)
+            result += "-" + MathLib::toString(-intvalue);
+        return result;
     }
     throw InternalError(nullptr, "Invalid ValueFlow Value type");
 }
@@ -6892,6 +6991,7 @@ void ValueFlow::setValues(TokenList *tokenlist, SymbolDatabase* symboldatabase,
     valueFlowGlobalStaticVar(tokenlist, settings);
     valueFlowPointerAlias(tokenlist);
     valueFlowLifetime(tokenlist, symboldatabase, errorLogger, settings);
+    valueFlowSymbolic(tokenlist, symboldatabase);
     valueFlowBitAnd(tokenlist);
     valueFlowSameExpressions(tokenlist);
     valueFlowConditionExpressions(tokenlist, symboldatabase, errorLogger, settings);
@@ -6901,6 +7001,7 @@ void ValueFlow::setValues(TokenList *tokenlist, SymbolDatabase* symboldatabase,
     while (n > 0 && values < getTotalValues(tokenlist)) {
         values = getTotalValues(tokenlist);
         valueFlowImpossibleValues(tokenlist, settings);
+        valueFlowSymbolicInfer(tokenlist, symboldatabase);
         valueFlowArrayBool(tokenlist);
         valueFlowRightShift(tokenlist, settings);
         valueFlowAfterMove(tokenlist, symboldatabase, settings);

lib/valueflow.h

@@ -26,6 +26,7 @@
 #include "mathlib.h"
 #include "utils.h"
 
+#include <cassert>
 #include <functional>
 #include <list>
 #include <string>
@@ -132,6 +133,13 @@ namespace ValueFlow {
             case ValueType::LIFETIME:
                 if (tokvalue != rhs.tokvalue)
                     return false;
+                break;
+            case ValueType::SYMBOLIC:
+                if (tokvalue != rhs.tokvalue)
+                    return false;
+                if (intvalue != rhs.intvalue)
+                    return false;
+                break;
             }
             return true;
         }
@@ -140,6 +148,7 @@ namespace ValueFlow {
         static void visitValue(T& self, F f) {
             switch (self.valueType) {
             case ValueType::INT:
+            case ValueType::SYMBOLIC:
             case ValueType::BUFFER_SIZE:
             case ValueType::CONTAINER_SIZE:
             case ValueType::ITERATOR_START:
@@ -175,6 +184,8 @@ namespace ValueFlow {
 
         template <class Compare>
         bool compareValue(const Value& rhs, Compare compare) const {
+            assert((!this->isSymbolicValue() && !rhs.isSymbolicValue()) ||
+                   (this->valueType == rhs.valueType && this->tokvalue == rhs.tokvalue));
             bool result = false;
             visitValue(
                 *this,
@@ -229,7 +240,19 @@ namespace ValueFlow {
 
         std::string infoString() const;
 
-        enum class ValueType { INT, TOK, FLOAT, MOVED, UNINIT, CONTAINER_SIZE, LIFETIME, BUFFER_SIZE, ITERATOR_START, ITERATOR_END } valueType;
+        enum class ValueType {
+            INT,
+            TOK,
+            FLOAT,
+            MOVED,
+            UNINIT,
+            CONTAINER_SIZE,
+            LIFETIME,
+            BUFFER_SIZE,
+            ITERATOR_START,
+            ITERATOR_END,
+            SYMBOLIC
+        } valueType;
         bool isIntValue() const {
             return valueType == ValueType::INT;
         }
@@ -263,6 +286,7 @@ namespace ValueFlow {
         bool isIteratorEndValue() const {
             return valueType == ValueType::ITERATOR_END;
         }
+        bool isSymbolicValue() const { return valueType == ValueType::SYMBOLIC; }
 
         bool isLocalLifetimeValue() const {
             return valueType == ValueType::LIFETIME && lifetimeScope == LifetimeScope::Local;

test/testvalueflow.cpp

@@ -24,16 +24,17 @@
 #include "tokenize.h"
 #include "valueflow.h"
 
-#include <simplecpp.h>
 #include <algorithm>
 #include <cmath>
+#include <cstdint>
+#include <cstring>
+#include <functional>
 #include <list>
 #include <map>
+#include <simplecpp.h>
 #include <string>
 #include <utility>
 #include <vector>
-#include <cstdint>
-#include <cstring>
 
 class TestValueFlow : public TestFixture {
 public:
@@ -142,6 +143,7 @@ private:
         TEST_CASE(valueFlowIdempotent);
         TEST_CASE(valueFlowUnsigned);
         TEST_CASE(valueFlowMod);
+        TEST_CASE(valueFlowSymbolic);
     }
 
     static bool isNotTokValue(const ValueFlow::Value &val) {
@@ -152,6 +154,8 @@ private:
         return !val.isLifetimeValue();
     }
 
+    static bool isNotUninitValue(const ValueFlow::Value& val) { return !val.isUninitValue(); }
+
     static bool isNotPossible(const ValueFlow::Value& val) {
         return !val.isPossible();
     }
@@ -177,6 +181,8 @@ private:
         for (const Token *tok = tokenizer.tokens(); tok; tok = tok->next()) {
             if (tok->str() == "x" && tok->linenr() == linenr) {
                 for (const ValueFlow::Value& val:tok->values()) {
+                    if (val.isSymbolicValue())
+                        continue;
                     if (val.isKnown() && val.intvalue == value)
                         return true;
                 }
@@ -186,6 +192,26 @@ private:
         return false;
     }
 
+    bool testValueOfXKnown(const char code[], unsigned int linenr, const std::string& expr, int value) {
+        // Tokenize..
+        Tokenizer tokenizer(&settings, this);
+        std::istringstream istr(code);
+        tokenizer.tokenize(istr, "test.cpp");
+
+        for (const Token* tok = tokenizer.tokens(); tok; tok = tok->next()) {
+            if (tok->str() == "x" && tok->linenr() == linenr) {
+                for (const ValueFlow::Value& val : tok->values()) {
+                    if (!val.isSymbolicValue())
+                        continue;
+                    if (val.isKnown() && val.intvalue == value && val.tokvalue->expressionString() == expr)
+                        return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
     bool testValueOfXImpossible(const char code[], unsigned int linenr, int value) {
         // Tokenize..
         Tokenizer tokenizer(&settings, this);
@@ -195,6 +221,8 @@ private:
         for (const Token *tok = tokenizer.tokens(); tok; tok = tok->next()) {
             if (tok->str() == "x" && tok->linenr() == linenr) {
                 for (const ValueFlow::Value& val:tok->values()) {
+                    if (val.isSymbolicValue())
+                        continue;
                     if (val.isImpossible() && val.intvalue == value)
                         return true;
                 }
@@ -213,6 +241,8 @@ private:
         for (const Token *tok = tokenizer.tokens(); tok; tok = tok->next()) {
             if (tok->str() == "x" && tok->linenr() == linenr) {
                 for (const ValueFlow::Value& val:tok->values()) {
+                    if (val.isSymbolicValue())
+                        continue;
                     if (val.isInconclusive() && val.intvalue == value)
                         return true;
                 }
@@ -1152,7 +1182,8 @@ private:
                "  y += 12;\n"
                "  if (y == 32) {}"
                "}\n";
-        ASSERT_EQUALS("5,Assuming that condition 'y==32' is not redundant\n"
+        ASSERT_EQUALS("2,x is assigned 'y' here.\n"
+                      "5,Assuming that condition 'y==32' is not redundant\n"
                       "4,Compound assignment '+=', assigned value is 20\n"
                       "2,Assignment 'x=y', assigned value is 20\n",
                       getErrorPathForX(code, 3U));
@@ -1173,7 +1204,10 @@ private:
                "  for (x = a; x < 50; x++) {}\n"
                "  b = x;\n"
                "}\n";
-        ASSERT_EQUALS("3,After for loop, x has value 50\n",
+        ASSERT_EQUALS("3,x is assigned 'a' here.\n"
+                      "3,x is incremented', new value is symbolic=a+1\n"
+                      "3,x is incremented', new value is symbolic=a+2\n"
+                      "3,After for loop, x has value 50\n",
                       getErrorPathForX(code, 4U));
     }
 
@@ -4298,6 +4332,7 @@ private:
                "    a = x + 1;\n"
                "}\n";
         values = tokenValues(code, "x +");
+        values.remove_if(&isNotUninitValue);
         ASSERT_EQUALS(true, values.empty());
 
         // #8494 - overloaded operator &
@@ -4682,6 +4717,7 @@ private:
     static std::string isPossibleContainerSizeValue(std::list<ValueFlow::Value> values,
             MathLib::bigint i,
             bool unique = true) {
+        values.remove_if(std::mem_fn(&ValueFlow::Value::isSymbolicValue));
         if (!unique)
             values.remove_if(&isNotPossible);
         if (values.size() != 1)
@@ -4698,6 +4734,7 @@ private:
     static std::string isImpossibleContainerSizeValue(std::list<ValueFlow::Value> values,
             MathLib::bigint i,
             bool unique = true) {
+        values.remove_if(std::mem_fn(&ValueFlow::Value::isSymbolicValue));
         if (!unique)
             values.remove_if(&isNotImpossible);
         if (values.size() != 1)
@@ -4714,6 +4751,7 @@ private:
     static std::string isInconclusiveContainerSizeValue(std::list<ValueFlow::Value> values,
             MathLib::bigint i,
             bool unique = true) {
+        values.remove_if(std::mem_fn(&ValueFlow::Value::isSymbolicValue));
         if (!unique)
             values.remove_if(&isNotInconclusive);
         if (values.size() != 1)
@@ -4728,6 +4766,7 @@ private:
     }
 
     static std::string isKnownContainerSizeValue(std::list<ValueFlow::Value> values, MathLib::bigint i, bool unique = true) {
+        values.remove_if(std::mem_fn(&ValueFlow::Value::isSymbolicValue));
         if (!unique)
             values.remove_if(&isNotKnown);
         if (values.size() != 1)
@@ -5898,6 +5937,68 @@ private:
         ASSERT_EQUALS(false, testValueOfXImpossible(code, 3U, 0));
         ASSERT_EQUALS(false, testValueOfXImpossible(code, 3U, 1));
     }
+
+    void valueFlowSymbolic() {
+        const char* code;
+
+        code = "int f(int i) {\n"
+               "    int j = i;\n"
+               "    int x = i;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 4U, "j", 0));
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 4U, "i", 0));
+
+        code = "int f(int i) {\n"
+               "    int j = i;\n"
+               "    int x = j;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 4U, "i", 0));
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 4U, "j", 0));
+
+        code = "void g(int&);\n"
+               "int f(int i) {\n"
+               "    int j = i;\n"
+               "    g(i);\n"
+               "    int x = i;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 6U, "i", 0));
+        ASSERT_EQUALS(false, testValueOfXKnown(code, 6U, "j", 0));
+
+        code = "int f(int i) {\n"
+               "    int j = i;\n"
+               "    j++;\n"
+               "    int x = i == j;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 5U, 0));
+
+        code = "int f(int i) {\n"
+               "    int j = i;\n"
+               "    i++;\n"
+               "    int x = i - j;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 5U, 1));
+
+        code = "int f(int i) {\n"
+               "    int j = i;\n"
+               "    i++;\n"
+               "    int x = i > j;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 5U, 1));
+
+        code = "int f(int i) {\n"
+               "    int j = i;\n"
+               "    j++;\n"
+               "    int x = j > i;\n"
+               "    return x;\n"
+               "}\n";
+        ASSERT_EQUALS(true, testValueOfXKnown(code, 5U, 1));
+    }
 };
 
 REGISTER_TEST(TestValueFlow)