Fix 9298 (#2476)

* Fix 9298

Tell cppcheck that strcpy returns its first argument, and use that
knowledge in checkTokenInsideExpression.

* Add missing unit tests in cmake

cfg/std.cfg

@@ -4641,7 +4641,7 @@ The obsolete function 'gets' is called. With 'gets' you'll get a buffer overrun
   </function>
   <!-- char *strcpy(char *desstr, const char *srcstr); -->
   <function name="strcpy,std::strcpy">
-    <returnValue type="char *"/>
+    <returnValue type="char *">arg1</returnValue>
     <noreturn>false</noreturn>
     <leak-ignore/>
     <arg nr="1" direction="out">

lib/checkleakautovar.cpp

@@ -743,8 +743,31 @@ const Token * CheckLeakAutoVar::checkTokenInsideExpression(const Token * const t
                 deallocUseError(tok, tok->str());
             } else if (Token::simpleMatch(tok->tokAt(-2), "= &")) {
                 varInfo->erase(tok->varId());
-            } else if (Token::Match(tok->previous(), "= %var% [;,)]")) {
-                varInfo->erase(tok->varId());
+            } else {
+                // check if tok is assigned into another variable
+                const Token *rhs = tok;
+                while (rhs->astParent()) {
+                    if (rhs->astParent()->str() == "=")
+                        break;
+                    rhs = rhs->astParent();
+                }
+                if (rhs->varId() == tok->varId()) {
+                    // simple assignment
+                    varInfo->erase(tok->varId());
+                } else if (rhs->str() == "(" && mSettings->library.returnValue(rhs->astOperand1()) != emptyString) {
+                    // #9298, assignment through return value of a function
+                    const std::string &returnValue = mSettings->library.returnValue(rhs->astOperand1());
+                    if (returnValue.compare(0, 3, "arg") == 0) {
+                        int argn;
+                        const Token *func = getTokenArgumentFunction(tok, argn);
+                        if (func) {
+                            const std::string arg = "arg" + std::to_string(argn + 1);
+                            if (returnValue == arg) {
+                                varInfo->erase(tok->varId());
+                            }
+                        }
+                    }
+                }
             }
         } else if (Token::Match(tok->previous(), "& %name% = %var% ;")) {
             varInfo->referenced.insert(tok->tokAt(2)->varId());
@@ -759,7 +782,7 @@ const Token * CheckLeakAutoVar::checkTokenInsideExpression(const Token * const t
         if (alloc.type == 0)
             alloc.status = VarInfo::NOALLOC;
         functionCall(tok, openingPar, varInfo, alloc, nullptr);
-        return openingPar->link();
+        return openingPar;
     }
 
     return nullptr;

test/CMakeLists.txt

@@ -59,6 +59,12 @@ if (BUILD_TESTS)
             add_fixture(${CMAKE_MATCH_1})
         endif()
     endforeach()
+    add_fixture("TestLeakAutoVarStrcpy")
+    add_fixture("TestLeakAutoVarWindows")
+    add_fixture("TestMemleakInFunction")
+    add_fixture("TestMemleakInClass")
+    add_fixture("TestMemleakStructMember")
+    add_fixture("TestMemleakNoVar")
 
     function(add_cfg CFG_TEST)
         set(options INCONCLUSIVE)

test/testleakautovar.cpp

@@ -2020,7 +2020,48 @@ class TestLeakAutoVar : public TestFixture {
 REGISTER_TEST(TestLeakAutoVar)
 
 
+class TestLeakAutoVarStrcpy: public TestFixture {
+public:
+    TestLeakAutoVarStrcpy() : TestFixture("TestLeakAutoVarStrcpy") {
+    }
+
+private:
+    Settings settings;
+
+    void check(const char code[]) {
+        // Clear the error buffer..
+        errout.str("");
+
+        // Tokenize..
+        Tokenizer tokenizer(&settings, this);
+        std::istringstream istr(code);
+        tokenizer.tokenize(istr, "test.cpp");
+
+        // Check for leaks..
+        CheckLeakAutoVar checkLeak;
+        settings.checkLibrary = true;
+        settings.addEnabled("information");
+        checkLeak.runChecks(&tokenizer, &settings, this);
+    }
+
+    void run() OVERRIDE {
+        LOAD_LIB_2(settings.library, "std.cfg");
+
+        TEST_CASE(returnedValue); // #9298
+    }
+
+    void returnedValue() { // #9298
+        check("char *m;\n"
+              "void strcpy_returnedvalue(const char* str)\n"
+              "{\n"
+              "    char* ptr = new char[strlen(str)+1];\n"
+              "    m = strcpy(ptr, str);\n"
+              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+};
 
+REGISTER_TEST(TestLeakAutoVarStrcpy)
 
 
 class TestLeakAutoVarWindows : public TestFixture {