Fix issue 8253: False negative: Comparison is always true (early return) (#3043)

Author: pfultz2

lib/forwardanalyzer.cpp

@@ -386,8 +386,6 @@ struct ForwardTraversal {
                 Token* endBlock = endCond->next()->link();
                 Token* condTok = getCondTok(tok);
                 Token* initTok = getInitTok(tok);
-                if (!condTok)
-                    return Progress::Break;
                 if (initTok && updateRecursive(initTok) == Progress::Break)
                     return Progress::Break;
                 if (Token::Match(tok, "for|while (")) {

test/testvalueflow.cpp

@@ -4270,6 +4270,16 @@ class TestValueFlow : public TestFixture {
                "}\n";
         ASSERT_EQUALS(false, testValueOfXKnown(code, 10U, 0));
         ASSERT_EQUALS(false, testValueOfXKnown(code, 10U, 1));
+
+        code = "void f() {\n"
+               "    const int size = arrayInfo.num(0);\n"
+               "    if (size <= 0)\n"
+               "        return;\n"
+               "    for (;;)\n"
+               "        if (size > 0) {}\n"
+               "}\n";
+        ASSERT_EQUALS(true, valueOfTok(code, "> 0").isKnown());
+        ASSERT_EQUALS(true, valueOfTok(code, "> 0").intvalue == 1);
     }
 
     static std::string isPossibleContainerSizeValue(const std::list<ValueFlow::Value> &values, MathLib::bigint i) {