Valgrind报告“无效的free() / delete / delete[]”

Question

我不确定是什么导致了这一切。

==18270== Invalid free() / delete / delete[]
==18270==    at 0x400576A: operator delete(void*) (vg_replace_malloc.c:342)
==18270==    by 0x80537F7: LCD::LCDControl::~LCDControl() (LCDControl.cpp:23)
==18270==    by 0x806C055: main (Main.cpp:22)
==18270==  Address 0x59e92c4 is 388 bytes inside a block of size 712 alloc'd
==18270==    at 0x40068AD: operator new(unsigned int) (vg_replace_malloc.c:224)
==18270==    by 0x8078033: LCD::DrvCrystalfontz::Get(std::string, LCD::LCDControl*, Json::Value*, std::string) (DrvCrystalfontz.cpp:652)
==18270==    by 0x8053F50: LCD::LCDControl::ConfigSetup() (LCDControl.cpp:71)
==18270==    by 0x80539F7: LCD::LCDControl::Start(int, char**) (LCDControl.cpp:31)
==18270==    by 0x806C025: main (Main.cpp:21)

下面是调用delete的LCDControl析构函数。

LCDControl::~LCDControl() {
    Shutdown();
    for(std::vector<std::string>::iterator it = display_keys_.begin();
        it != display_keys_.end(); it++) {
        Error("Deleting %s %p", (*it).c_str(), devices_text_[*it]);
        if(devices_text_.find(*it) != devices_text_.end() && devices_text_[*it])
            delete devices_text_[*it]; // line 23
    }
    //delete app_;
}

下面是Crystalfontz::Get()

switch(m->GetProtocol()) {
    case 1:
        return new Protocol1(name, m, v, config);
        break;
    case 2:
        return new Protocol2(name, m, v, config); // line 652
        break;
    case 3:
        return new Protocol3(name, m, v, config, scab);
        break;
    default:
        Error("Internal error. Model has bad protocol: <%s>",
            m->GetName().c_str());
        break;

devices_text_：

std::map<std::string, Generic <LCDText>*> devices_text_;

LCDControl::ConfigSetup()，

void LCDControl::ConfigSetup() {
    if(!CFG_Get_Root()) return;
    Json::Value::Members keys = CFG_Get_Root()->getMemberNames();

    for(std::vector<std::string>::iterator it = keys.begin(); it != keys.end(); it++ ) {
        if(it->find("display_", 0) != std::string::npos) {
            Json::Value *display = CFG_Fetch_Raw(CFG_Get_Root(), it->c_str());
            Json::Value *driver = CFG_Fetch_Raw(display, "driver");
            if(!driver) {
                Error("CFG: Must specify driver <%s>", it->c_str());
                continue;
            }
            Json::Value *rows = CFG_Fetch_Raw(display, "rows", new Json::Value(-1));
            /*if(!rows->isNumeric() || rows->asInt() == -1) {
                Error("Display <%s> requires number of rows to initialize.", it->c_str());
                delete display;
                delete driver;
                continue;
            }*/
            Json::Value *cols = CFG_Fetch_Raw(display, "cols", new Json::Value(-1));
            /*if(!cols->isNumeric() || rows->asInt() == -1) {
                Error("Display <%s> requires number of columns to initialize.", it->c_str());
                delete display;
                delete driver;
                delete rows;
                continue;
            }*/

            Json::Value *model = CFG_Fetch_Raw(display, "model");
            if(driver->asString() == "crystalfontz") {
                if(model) {
                    devices_text_[*it] = DrvCrystalfontz::Get(*it, this,
                        CFG_Get_Root(), model->asString()); // line 71
                } else {
                    Error("Device <%s> requires a model.", it->c_str());
                    delete display;
                    delete driver;
                    delete rows;
                    delete cols;
                    continue;
                }
            } else if(driver->asString() == "qt") {
                devices_text_[*it] = new DrvQt(*it, this, CFG_Get_Root(),
                    rows->asInt(), cols->asInt());

            } else if(driver->asString() == "pertelian") {
                //devices_text_[*it] = new DrvPertelian(this, CFG_Get_Root(), rows->asInt(), cols->asInt());

            } else
                continue;
            if(model) delete model;
            delete display;
            delete driver;
            delete rows;
            delete cols;
        }

    }

    for(std::map<std::string, Generic<LCDText> *>::iterator it =
        devices_text_.begin(); it != devices_text_.end(); it++) {
        display_keys_.push_back(it->first);
        Error("Starting <%s> %p", it->first.c_str(), it->second);
        Generic<LCDText> *device = it->second;
        device->CFGSetup(it->first);
        device->Connect();
        device->SetupDevice();
        device->BuildLayouts();
        device->StartLayout();
    }
}

Answer 1

我猜Protocol1等人。是一些SuperProtocol的子类

devices_text_[*it]假设它包含SuperProtocol类型的内容，因此delete devices_text_[*it]调用SuperProtocol::~ SuperProtocol()。

但是，如果您正在析构一个Protocol1，那么您真正想要调用的是Protocol1::~Protocol1()；只有当您将SuperProtocol::~ SuperProtocol()标记为virtual时，这才有效。

Answer 2

与其遍历这些键，在map中找到它，然后删除它，为什么不在map中迭代删除呢？我会做一个函数器并使用for_each (这不是一个指导方针或任何东西，只是我的观点)，

typedef Generic<LCDText> GenericLCDText;
typedef std::map<std::string, GenericLCDText*> GenericLCDTextMap;
typedef GenericLCDTextMap::value_type GenericLCDTextPair;

struct device_text_deleter : std::unary_function<const GenericLCDTextPair&, void>
{
    void operator()(const GenericLCDTextPair& pPair)
    {
        Error("Deleting %s %p", pPair.first.c_str(), pPair.second);

        delete pPair.second;        
    }
}

std::for_each(devices_text_.begin(), devices_text_.end(), device_text_deleter());
_devices.text_.clear(); // optional, removes the deleted pointers. unnecessary
                        // if this is run in the destructor, since map goes away
                        // shortly after

也就是说，您的代码将通过以下方式进行改进：

// typedef's for readability (would be in header, maybe private)
typedef std::vector<std::string> StringVector;
typedef Generic<LCDText> GenericLCDText;
typedef std::map<std::string, GenericLCDText*> GenericLCDTextMap;

for(StringVector::iterator it = display_keys_.begin();
    it != display_keys_.end(); it++)
{
    // find first! otherwise you're looking up the pair every time
    GenericLCDTextMap::iterator pair = devices_text_.find(*it);

    if (p != devices_text_.end())
    {
        // operator-> is overloaded for iterators but might as well use
        // the pair now.
        Error("Deleting %s %p", pair->first.c_str(), pair->second);

        // no need to check for null, delete null is a-ok
        delete pair->second;
    }
}

希望这将使发现错误变得更容易。确保您使用的任何基类都有虚拟析构函数。

检查你没有在向量中添加两次字符串(这将是“修复”的购买，只是迭代通过地图，尽管你会想要找出为什么存在重复的第一个地方)，等等。

我以前从来没有尝试过，但可能会添加一个双删除宏的东西(完全未经测试)：

#define DOUBLE_DELETE_GAURD static bool x = false; assert(x == false); x = true;

然后把它添加到你的析构函数中。如果双击delete，而静态布尔值仍然存在，则断言将失败。然而，这完全是在未定义的la-la领域。

Answer 3

会不会是这样？

1. display_keys_多次包含相同的字符串，并且在devices_text_

中

• 此字符串具有关联的Generic <LCDText>*

在这种情况下，指针将被赋予delete两次，这是不合法的……