Fix 11158: FP zerodiv in loop (#4356)

* Fix 11158: FP zerodiv in loop

* Format

* Add another test

* Format

* Fix FP

* Format

lib/valueflow.cpp

@@ -510,6 +510,10 @@ void combineValueProperties(const ValueFlow::Value &value1, const ValueFlow::Val
         result->setInconclusive();
     else
         result->setPossible();
+    if (value1.tokvalue)
+        result->tokvalue = value1.tokvalue;
+    else if (value2.tokvalue)
+        result->tokvalue = value2.tokvalue;
     if (value1.isSymbolicValue()) {
         result->valueType = value1.valueType;
         result->tokvalue = value1.tokvalue;
@@ -2465,10 +2469,7 @@ struct ValueFlowAnalyzer : Analyzer {
             // Check if its assigned to the same value
             if (value && !value->isImpossible() && Token::simpleMatch(tok->astParent(), "=") && astIsLHS(tok) &&
                 astIsIntegral(tok->astParent()->astOperand2(), false)) {
-                std::vector<MathLib::bigint> result =
-                    evaluateInt(tok->astParent()->astOperand2(), [&] {
-                    return ProgramMemory{getProgramState()};
-                });
+                std::vector<MathLib::bigint> result = evaluateInt(tok->astParent()->astOperand2());
                 if (!result.empty() && value->equalTo(result.front()))
                     return Action::Idempotent;
             }
@@ -2541,24 +2542,30 @@ struct ValueFlowAnalyzer : Analyzer {
                 return Action::None;
             return Action::Read | Action::Write;
         }
-        if (parent && parent->isAssignmentOp() && astIsLHS(tok) &&
-            parent->astOperand2()->hasKnownValue()) {
+        if (parent && parent->isAssignmentOp() && astIsLHS(tok)) {
             const Token* rhs = parent->astOperand2();
-            const ValueFlow::Value* rhsValue = rhs->getKnownValue(ValueFlow::Value::ValueType::INT);
+            std::vector<MathLib::bigint> result = evaluateInt(rhs);
+            if (!result.empty()) {
+                ValueFlow::Value rhsValue{result.front()};
                 Action a;
-            if (!rhsValue || !evalAssignment(*value, getAssign(parent, d), *rhsValue))
+                if (!evalAssignment(*value, getAssign(parent, d), rhsValue))
                     a = Action::Invalid;
                 else
                     a = Action::Write;
                 if (parent->str() != "=") {
-                a |= Action::Read;
+                    a |= Action::Read | Action::Incremental;
                 } else {
-                if (rhsValue && !value->isImpossible() && value->equalValue(*rhsValue))
+                    if (!value->isImpossible() && value->equalValue(rhsValue))
                         a = Action::Idempotent;
+                    if (tok->exprId() != 0 &&
+                        findAstNode(rhs, [&](const Token* child) {
+                        return tok->exprId() == child->exprId();
+                    }))
                         a |= Action::Incremental;
                 }
                 return a;
             }
+        }
 
         // increment/decrement
         if (Token::Match(tok->astParent(), "++|--")) {
@@ -2576,10 +2583,11 @@ struct ValueFlowAnalyzer : Analyzer {
         if (value->isLifetimeValue())
             return;
         if (tok->astParent()->isAssignmentOp()) {
-            const ValueFlow::Value* rhsValue =
-                tok->astParent()->astOperand2()->getKnownValue(ValueFlow::Value::ValueType::INT);
-            assert(rhsValue);
-            if (evalAssignment(*value, getAssign(tok->astParent(), d), *rhsValue)) {
+            const Token* rhs = tok->astParent()->astOperand2();
+            std::vector<MathLib::bigint> result = evaluateInt(rhs);
+            assert(!result.empty());
+            ValueFlow::Value rhsValue{result.front()};
+            if (evalAssignment(*value, getAssign(tok->astParent(), d), rhsValue)) {
                 std::string info("Compound assignment '" + tok->astParent()->str() + "', assigned value is " +
                                  value->infoString());
                 if (tok->astParent()->str() == "=")
@@ -2777,6 +2785,12 @@ struct ValueFlowAnalyzer : Analyzer {
         }
         return result;
     }
+    std::vector<MathLib::bigint> evaluateInt(const Token* tok) const
+    {
+        return evaluateInt(tok, [&] {
+            return ProgramMemory{getProgramState()};
+        });
+    }
 
     std::vector<MathLib::bigint> evaluate(Evaluate e, const Token* tok, const Token* ctx = nullptr) const override
     {
@@ -5536,6 +5550,28 @@ static void valueFlowAfterAssign(TokenList *tokenlist, SymbolDatabase* symboldat
                     return value.tokvalue->exprId() == tok->astOperand1()->exprId();
                 return false;
             });
+            // Find references to LHS in RHS
+            auto isIncremental = [&](const Token* tok2) -> bool {
+                return findAstNode(tok2,
+                                   [&](const Token* child) {
+                    return child->exprId() == tok->astOperand1()->exprId();
+                });
+            };
+            // Check symbolic values as well
+            const bool incremental = isIncremental(tok->astOperand2()) ||
+                                     std::any_of(values.begin(), values.end(), [&](const ValueFlow::Value& value) {
+                if (!value.isSymbolicValue())
+                    return false;
+                return isIncremental(value.tokvalue);
+            });
+            // Remove values from the same assignment if it is incremental
+            if (incremental) {
+                values.remove_if([&](const ValueFlow::Value& value) {
+                    if (value.tokvalue)
+                        return value.tokvalue == tok->astOperand2();
+                    return false;
+                });
+            }
             // If assignment copy by value, remove Uninit values..
             if ((tok->astOperand1()->valueType() && tok->astOperand1()->valueType()->pointer == 0) ||
                 (tok->astOperand1()->variable() && tok->astOperand1()->variable()->isReference() && tok->astOperand1()->variable()->nameToken() == tok->astOperand1()))

test/testother.cpp

@@ -66,6 +66,7 @@ private:
         TEST_CASE(zeroDiv13);
         TEST_CASE(zeroDiv14); // #1169
         TEST_CASE(zeroDiv15); // #8319
+        TEST_CASE(zeroDiv16); // #11158
 
         TEST_CASE(zeroDivCond); // division by zero / useless condition
 
@@ -611,6 +612,31 @@ private:
         ASSERT_EQUALS("[test.cpp:4]: (error) Division by zero.\n", errout.str());
     }
 
+    // #11158
+    void zeroDiv16()
+    {
+        check("int f(int i) {\n"
+              "    int number = 10, a = 0;\n"
+              "    for (int count = 0; count < 2; count++) {\n"
+              "        a += (i / number) % 10;\n"
+              "        number = number / 10;\n"
+              "    }\n"
+              "    return a;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
+        check("int f(int i) {\n"
+              "    int number = 10, a = 0;\n"
+              "    for (int count = 0; count < 2; count++) {\n"
+              "        int x = number / 10;\n"
+              "        a += (i / number) % 10;\n"
+              "        number = x;\n"
+              "    }\n"
+              "    return a;\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void zeroDivCond() {
         check("void f(unsigned int x) {\n"
               "  int y = 17 / x;\n"