Fix issue 7324: valueFlowForward : decrement (#2737)

lib/forwardanalyzer.cpp

@@ -211,6 +211,8 @@ struct ForwardTraversal {
     Progress updateLoop(Token* endBlock, Token* condTok, Token* initTok = nullptr, Token* stepTok = nullptr) {
         ForwardAnalyzer::Action bodyAnalysis = analyzeScope(endBlock);
         ForwardAnalyzer::Action allAnalysis = bodyAnalysis;
+        if (condTok)
+            allAnalysis |= analyzeRecursive(condTok);
         if (initTok)
             allAnalysis |= analyzeRecursive(initTok);
         if (stepTok)
@@ -422,9 +424,13 @@ struct ForwardTraversal {
                 tok = endBlock;
             } else if (Token::simpleMatch(tok, "do {")) {
                 Token* endBlock = tok->next()->link();
-                if (updateLoop(endBlock, nullptr) == Progress::Break)
+                Token* condTok = Token::simpleMatch(endBlock, "} while (") ? endBlock->tokAt(2)->astOperand2() : nullptr;
+                if (updateLoop(endBlock, condTok) == Progress::Break)
                     return Progress::Break;
-                tok = endBlock;
+                if (condTok)
+                    tok = endBlock->linkAt(2)->next();
+                else
+                    tok = endBlock;
             } else if (Token::Match(tok, "assert|ASSERT (")) {
                 const Token* condTok = tok->next()->astOperand2();
                 bool checkThen, checkElse;

lib/valueflow.cpp

@@ -790,6 +790,38 @@ static void setTokenValue(Token* tok, const ValueFlow::Value &value, const Setti
         }
     }
 
+    // increment
+    else if (parent->str() == "++") {
+        for (const ValueFlow::Value &val : tok->values()) {
+            if (!val.isIntValue() && !val.isFloatValue())
+                continue;
+            ValueFlow::Value v(val);
+            if (parent == tok->previous()) {
+                if (v.isIntValue())
+                    v.intvalue = v.intvalue + 1;
+                else
+                    v.floatValue = v.floatValue + 1.0;
+            }
+            setTokenValue(parent, v, settings);
+        }
+    }
+
+    // decrement
+    else if (parent->str() == "--") {
+        for (const ValueFlow::Value &val : tok->values()) {
+            if (!val.isIntValue() && !val.isFloatValue())
+                continue;
+            ValueFlow::Value v(val);
+            if (parent == tok->previous()) {
+                if (v.isIntValue())
+                    v.intvalue = v.intvalue - 1;
+                else
+                    v.floatValue = v.floatValue - 1.0;
+            }
+            setTokenValue(parent, v, settings);
+        }
+    }
+
     // Array element
     else if (parent->str() == "[" && parent->isBinaryOp()) {
         for (const ValueFlow::Value &value1 : parent->astOperand1()->values()) {

test/testother.cpp

@@ -57,6 +57,7 @@ private:
         TEST_CASE(zeroDiv10);
         TEST_CASE(zeroDiv11);
         TEST_CASE(zeroDiv12);
+        TEST_CASE(zeroDiv13);
 
         TEST_CASE(zeroDivCond); // division by zero / useless condition
 
@@ -560,6 +561,16 @@ private:
               "}\n");
         ASSERT_EQUALS("[test.cpp:2]: (error) Division by zero.\n", errout.str());
     }
+    void zeroDiv13() {
+        // #7324
+        check("int f () {\n"
+              "    int dividend = 10;\n"
+              "        int divisor = 1;\n"
+              "    dividend = dividend / (--divisor);\n"
+              "    return dividend;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:4]: (error) Division by zero.\n", errout.str());
+    }
 
     void zeroDivCond() {
         check("void f(unsigned int x) {\n"