Question

我编写了一些C ++代码来实现自己的堆栈。但是，当我使用valgrind进行检查时，它表示可能存在内存泄漏。我检查了这么久但仍然找不到它。

这是代码：

#ifndef RE_STACK_H
#define RE_STACK_H

#include <cstdlib>
#include "general.h"

template <typename T>
class Stack {
private:
    T* bottom;
    T* top;
    T* sentinel;
    uint32 size;
public:
    Stack(uint32 size = 30);
    ~Stack();
    void push(const T&);
    T pop();
    void expand();
};

template <typename T>
Stack<T>::Stack(uint32 size) :size(size){
    bottom = top = static_cast<T*>(malloc(size * sizeof(T)));
    sentinel = bottom + size * sizeof(T);
}

template <typename T>
Stack<T>::~Stack() {
    while (top-- != bottom){
        top->~T();
    }
    free(bottom);
}

template <typename T>
void Stack<T>::push(const T& item){
    if(top == sentinel){
        expand();
    }
    new(top++)T(item);
}

template <typename T>
T Stack<T>::pop() {
    if(bottom == top){
        return 0;
    }
    T re = *--top;
    top->~T();
    return re;
}

template <typename T>
void Stack<T>::expand() {
    size *= 2;
    uint32 temp = top - bottom;
    bottom = static_cast<T*>(realloc(bottom, size * sizeof(T)));
    top = bottom + temp;
    sentinel = bottom + size * sizeof(T);
}
#endif //RE_STACK_H




#include <iostream>
#include "NTL/Stack.h"

int main() {
    return 0;
}

这是来自valgrind的错误信息：

==33519== HEAP SUMMARY:
==33519==     in use at exit: 22,216 bytes in 190 blocks
==33519==   total heap usage: 256 allocs, 66 frees, 27,992 bytes allocated
==33519== 
==33519== 2,064 bytes in 1 blocks are possibly lost in loss record 58 of 63
==33519==    at 0x10000817C: malloc_zone_malloc (in /usr/local/Cellar/valgrind/3.11.0/lib/valgrind/vgpreload_memcheck-amd64-darwin.so)
==33519==    by 0x1005E1EFD: _objc_copyClassNamesForImage (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D5182: protocols() (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D5093: readClass(objc_class*, bool, bool) (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D2C13: gc_init (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005DA24E: objc_initializeClassPair_internal(objc_class*, char const*, objc_class*, objc_class*) (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005E7132: layout_string_create (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D583C: realizeClass(objc_class*) (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D5300: copySwiftV1MangledName(char const*, bool) (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D52E9: copySwiftV1MangledName(char const*, bool) (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D52E9: copySwiftV1MangledName(char const*, bool) (in /usr/lib/libobjc.A.dylib)
==33519==    by 0x1005D52E9: copySwiftV1MangledName(char const*, bool) (in /usr/lib/libobjc.A.dylib)
==33519== 
==33519== LEAK SUMMARY:
==33519==    definitely lost: 0 bytes in 0 blocks
==33519==    indirectly lost: 0 bytes in 0 blocks
==33519==      possibly lost: 2,064 bytes in 1 blocks
==33519==    still reachable: 0 bytes in 0 blocks
==33519==         suppressed: 20,152 bytes in 189 blocks
==33519== 
==33519== For counts of detected and suppressed errors, rerun with: -v
==33519== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 18 from 18)

我看过几条评论，我想解释一下：

我使用malloc()和free()而不是new和delete，因为我想分开内存分配和类构造的过程，你可以在我的析构函数中看到，我在那里释放内存。每次我pop()一个项目，我都会使用类的析构函数来确保它被正确破坏，但是我没有释放内存，因为我以后可能会使用它。
感谢Joachim Pileborg，sentinel = bottom + size * sizeof(T);应更改为sentinel = bottom + size;，但这并不是valgrind说 1个块中的2,064个字节可能丢失的原因在损失记录58 of 63
我知道我没有遵循3/5规则，事实上我没有完成代码，我将编写复制构造函数并稍后分配运算符，我只想测试代码时并不大。
请不要说代码是垃圾，只要看一眼就注意我使用malloc();如果您看到STL的源代码，您将看到分配器的工作方式

Answer 1

最后我认为这是因为valgrind。我不知道为什么，即使我写的跟注码一样简单，我也有错误......

int main(int argc, char* argv[]){
    return 0;
}

无论如何，感谢那些帮助我找出错误的人：

sentinel只需要添加尺寸......
realloc无法帮助我调用析构函数。

这段C ++代码怎么会出现内存泄漏？

1 个答案: