Fixed #5301 (False positive: (error) Division by zero - variables read from input stream)

lib/tokenize.cpp

@@ -6758,7 +6758,7 @@ bool Tokenizer::simplifyKnownVariablesSimplify(Token **tok2, Token *tok3, unsign
         if (isCPP() && Token::Match(tok3, (">> " + structname + " %varid%").c_str(), varid)) {
             // bailout for such code:   ; std :: cin >> i ;
             const Token *prev = tok3->previous();
-            while (prev && prev->str() != "return" && (prev->isName() || prev->str() == "::"))
+            while (prev && prev->str() != "return" && Token::Match(prev, "%var%|::|*"))
                 prev = prev->previous();
             if (Token::Match(prev, ";|{|}|>>"))
                 break;

lib/valueflow.cpp

@@ -564,6 +564,18 @@ static void valueFlowAfterAssign(TokenList *tokenlist, ErrorLogger *errorLogger,
                     break;
                 }
 
+                // bailout: possible assignment using >>
+                if (Token::Match(tok2->previous(), ">> %var% >>|;")) {
+                    const Token *parent = tok2->previous();
+                    while (Token::simpleMatch(parent,">>"))
+                        parent = parent->astParent();
+                    if (!parent) {
+                        if (settings->debugwarnings)
+                            bailout(tokenlist, errorLogger, tok2, "Possible assignment of " + tok2->str() + " using >>");
+                        break;
+                    }
+                }
+
                 // skip if variable is conditionally used in ?: expression
                 if (const Token *parent = skipValueInConditionalExpression(tok2)) {
                     if (settings->debugwarnings)

test/testtokenize.cpp

@@ -188,6 +188,7 @@ private:
         TEST_CASE(simplifyKnownVariables53);    // references
         TEST_CASE(simplifyKnownVariables54);    // #4913 'x' is not 0 after *--x=0;
         TEST_CASE(simplifyKnownVariables55);    // pointer alias
+        TEST_CASE(simplifyKnownVariables56);    // ticket #5301 - >>
         TEST_CASE(simplifyKnownVariablesIfEq1); // if (a==5) => a is 5 in the block
         TEST_CASE(simplifyKnownVariablesIfEq2); // if (a==5) { buf[a++] = 0; }
         TEST_CASE(simplifyKnownVariablesIfEq3); // #4708 - if (a==5) { buf[--a] = 0; }
@@ -2888,6 +2889,11 @@ private:
         ASSERT_EQUALS("void f ( ) { int a ; if ( x > a ) { } }", tokenizeAndStringify("void f() { int a; int *p=&a; if (x>*p) {} }", true));
     }
 
+    void simplifyKnownVariables56() { // ticket #5301 - >>
+        ASSERT_EQUALS("void f ( ) { int a ; a = 0 ; int b ; b = 0 ; * p >> a >> b ; return a / b ; }",
+                      tokenizeAndStringify("void f() { int a=0,b=0; *p>>a>>b; return a/b; }", true));
+    }
+
     void simplifyKnownVariablesIfEq1() {
         const char code[] = "void f(int x) {\n"
                             "    if (x==5) {\n"

test/testvalueflow.cpp

@@ -498,6 +498,13 @@ private:
                "}";
         ASSERT_EQUALS(false, testValueOfX(code, 4U, 2));
 
+        code = "void f() {\n"
+               "    static int x = 2;\n"
+               "    a >> x;\n"
+               "    return x;\n"
+               "}";
+        ASSERT_EQUALS(false, testValueOfX(code, 4U, 2));
+
         // function
         code = "void f() {\n"
                "    char *x = 0;\n"