Fix #9653 FP leakReturnValNotUsed although (void) is specified (#4431)

lib/checkfunctions.cpp

@@ -268,9 +268,9 @@ void CheckFunctions::checkIgnoredReturnValue()
             if ((!tok->function() || !Token::Match(tok->function()->retDef, "void %name%")) &&
                 !WRONG_DATA(!tok->next()->astOperand1(), tok)) {
                 const Library::UseRetValType retvalTy = mSettings->library.getUseRetValType(tok);
-                if (mSettings->severity.isEnabled(Severity::warning) &&
-                    ((retvalTy == Library::UseRetValType::DEFAULT) ||
-                     (tok->function() && tok->function()->isAttributeNodiscard())))
+                const bool warn = (tok->function() && tok->function()->isAttributeNodiscard()) || // avoid duplicate warnings for resource-allocating functions
+                                  (retvalTy == Library::UseRetValType::DEFAULT && mSettings->library.getAllocFuncInfo(tok) == nullptr);
+                if (mSettings->severity.isEnabled(Severity::warning) && warn)
                     ignoredReturnValueError(tok, tok->next()->astOperand1()->expressionString());
                 else if (mSettings->severity.isEnabled(Severity::style) &&
                          retvalTy == Library::UseRetValType::ERROR_CODE)

lib/checkmemoryleak.cpp

@@ -274,6 +274,16 @@ bool CheckMemoryLeak::isReopenStandardStream(const Token *tok) const
     return false;
 }
 
+bool CheckMemoryLeak::isOpenDevNull(const Token *tok) const
+{
+    if (mSettings_->posix() && tok->str() == "open" && numberOfArguments(tok) == 2) {
+        const Token* arg = getArguments(tok).at(0);
+        if (Token::simpleMatch(arg, "\"/dev/null\""))
+            return true;
+    }
+    return false;
+}
+
 //--------------------------------------------------------------------------
 
 
@@ -1053,10 +1063,12 @@ void CheckMemoryLeakNoVar::checkForUnusedReturnValue(const Scope *scope)
 
         if (isReopenStandardStream(tok))
             continue;
+        if (isOpenDevNull(tok))
+            continue;
 
         // get ast parent, skip casts
         const Token *parent = isNew ? tok->astParent() : tok->next()->astParent();
-        while (parent && parent->str() == "(" && !parent->astOperand2())
+        while (parent && parent->isCast())
             parent = parent->astParent();
 
         bool warn = true;

lib/checkmemoryleak.h

@@ -118,6 +118,11 @@ public:
      * @param tok token to check
      */
     bool isReopenStandardStream(const Token *tok) const;
+    /**
+     * Check if token opens /dev/null
+     * @param tok token to check
+     */
+    bool isOpenDevNull(const Token *tok) const;
     /**
      * Report that there is a memory leak (new/malloc/etc)
      * @param tok token where memory is leaked

test/cfg/gtk.c

@@ -73,7 +73,6 @@ void validCode(int argInt, GHashTableIter * hash_table_iter, GHashTable * hash_t
 
 void g_malloc_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_malloc(8);
 
@@ -86,7 +85,6 @@ void g_malloc_test()
 
 void g_malloc0_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_malloc0(8);
 
@@ -99,7 +97,6 @@ void g_malloc0_test()
 
 void g_malloc_n_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_malloc_n(8, 1);
 
@@ -112,7 +109,6 @@ void g_malloc_n_test()
 
 void g_malloc0_n_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_malloc0_n(8, 1);
 
@@ -125,7 +121,6 @@ void g_malloc0_n_test()
 
 void g_try_malloc_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_try_malloc(8);
 
@@ -138,7 +133,6 @@ void g_try_malloc_test()
 
 void g_try_malloc0_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_try_malloc0(8);
 
@@ -151,7 +145,6 @@ void g_try_malloc0_test()
 
 void g_try_malloc_n_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_try_malloc_n(8, 1);
 
@@ -164,7 +157,6 @@ void g_try_malloc_n_test()
 
 void g_try_malloc0_n_test()
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_try_malloc0_n(8, 1);
 
@@ -374,7 +366,6 @@ void g_error_new_test()
     printf("%p", pNew1);
     g_error_free(pNew1);
 
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     g_error_new(1, -2, "a %d", 1);
 

test/cfg/posix.c

@@ -838,7 +838,6 @@ void nullPointer(char *p, int fd, pthread_mutex_t mutex)
     // cppcheck-suppress unreadVariable
     // cppcheck-suppress nullPointer
     int ret = access(NULL, 0);
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     // cppcheck-suppress nullPointer
     fdopen(fd, NULL);
@@ -978,7 +977,6 @@ void noleak(int x, int y, int z)
 
 void ignoredReturnValue(void *addr, int fd)
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     mmap(addr, 255, PROT_NONE, MAP_PRIVATE, fd, 0);
     // cppcheck-suppress ignoredReturnValue
@@ -1065,7 +1063,6 @@ void uninitvar(int fd)
     // cppcheck-suppress uninitvar
     int access_ret = access("file", x3);
 
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     // cppcheck-suppress uninitvar
     fdopen(x4, "rw");

test/cfg/std.c

@@ -287,7 +287,6 @@ void pointerLessThanZero_aligned_alloc(void)
 
 void unusedRetVal_aligned_alloc(void)
 {
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     aligned_alloc(8, 16);
 }

test/cfg/windows.cpp

@@ -681,7 +681,6 @@ void ignoredReturnValue()
     // cppcheck-suppress leakReturnValNotUsed
     CreateEventEx(NULL, L"test", CREATE_EVENT_INITIAL_SET, EVENT_MODIFY_STATE);
 
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     _malloca(10);
     // cppcheck-suppress ignoredReturnValue
@@ -693,10 +692,8 @@ void ignoredReturnValue()
 
     // cppcheck-suppress ignoredReturnValue
     GetProcessHeap();
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     HeapAlloc(GetProcessHeap(), 0, 10);
-    // cppcheck-suppress ignoredReturnValue
     // cppcheck-suppress leakReturnValNotUsed
     HeapReAlloc(GetProcessHeap(), 0, 1, 0);
 

test/testmemleak.cpp

@@ -2311,6 +2311,7 @@ private:
         TEST_CASE(getAllocationType);
 
         TEST_CASE(crash1); // #10729
+        TEST_CASE(openDevNull); // #9653
     }
 
     void functionParameter() {
@@ -2852,6 +2853,14 @@ private:
               "}");
         ASSERT_EQUALS("", errout.str());
     }
+
+    void openDevNull() {
+        check("void f() {\n" // #9653
+              "    (void)open(\"/dev/null\", O_RDONLY);\n"
+              "    open(\"/dev/null\", O_WRONLY);\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+    }
 };
 REGISTER_TEST(TestMemleakNoVar)