Fix #14392 FN knownConditionTrueFalse (assigning function call result) (#8118)

Author: chrchr-github

.selfcheck_suppressions

@@ -40,5 +40,6 @@ naming-privateMemberVariable:externals/tinyxml2/tinyxml2.h
 functionStatic:externals/tinyxml2/tinyxml2.cpp
 funcArgNamesDifferent:externals/tinyxml2/tinyxml2.cpp
 nullPointerRedundantCheck:externals/tinyxml2/tinyxml2.cpp
+knownConditionTrueFalse:externals/tinyxml2/tinyxml2.cpp
 useStlAlgorithm:externals/simplecpp/simplecpp.cpp
 missingMemberCopy:externals/simplecpp/simplecpp.h

lib/checkcondition.cpp

@@ -1545,6 +1545,8 @@ void CheckCondition::alwaysTrueFalse()
                     condition = parent->astParent()->astParent()->previous();
                 else if (Token::Match(tok, "%comp%"))
                     condition = tok;
+                else if (tok->str() == "(" && astIsBool(parent) && Token::Match(parent, "%assign%"))
+                    condition = tok;
                 else
                     continue;
             }
@@ -1647,11 +1649,20 @@ void CheckCondition::alwaysTrueFalse()
     }
 }
 
+static std::string getConditionString(const Token* condition)
+{
+    if (Token::simpleMatch(condition, "return"))
+        return "Return value";
+    if (Token::simpleMatch(condition, "(") && Token::Match(condition->astParent(), "%assign%"))
+        return "Assigned value";
+    return "Condition";
+}
+
 void CheckCondition::alwaysTrueFalseError(const Token* tok, const Token* condition, const ValueFlow::Value* value)
 {
     const bool alwaysTrue = value && (value->intvalue != 0 || value->isImpossible());
     const std::string expr = tok ? tok->expressionString() : std::string("x");
-    const std::string conditionStr = (Token::simpleMatch(condition, "return") ? "Return value" : "Condition");
+    const std::string conditionStr = getConditionString(condition);
     const std::string errmsg = conditionStr + " '" + expr + "' is always " + bool_to_string(alwaysTrue);
     ErrorPath errorPath = getErrorPath(tok, value, errmsg);
     reportError(std::move(errorPath),

test/testcondition.cpp

@@ -4806,6 +4806,19 @@ class TestCondition : public TestFixture {
               "    }\n"
               "}\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("struct S {\n" // #14392
+              "    bool g() const { return m; }\n"
+              "    bool m{};\n"
+              "};\n"
+              "bool f(S s) {\n"
+              "    if (s.g()) {\n"
+              "        bool b = s.g();\n"
+              "        return b;\n"
+              "    }\n"
+              "    return false;\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:6:12] -> [test.cpp:7:21]: (style) Assigned value 's.g()' is always true [knownConditionTrueFalse]\n", errout_str());
     }
 
     void alwaysTrueSymbolic()