Result analysis

Part 2

​ For part 2, we finish the detection of memory allocation and also finish the memory leak for extension.

​ The history_*.log record the history of memory release and detect.

​ The result_*.log record the memory leaking.

​ There is an example bellow.

Implementatiom

Detect memory allocation and release in a process

Before work

​ In order to detect the memory allocation and release, we need to know the basic ways of memory allocation and release.

​ For memory allocation there are 5 types:

• new

• new[]

• malloc

• calloc

• realloc

​ And only 3 types for memory free:

• delete
• delete[]
• free

​ Thus we only need to overwrite those 8 functions to detect memory allocation and release.

Data structure

​ As before work analysis, we need to record the informations when those 8 methods runs.

​ We plans to output one .log document to record both informations of allocation and free.

​ Also, we choose a double linked list to record the pointer that still not free.

​ For each node, we record the 4 kinds of informations:

• pointer
• size
• file name
• file line

​ And it is packaging in to the structure MemoryInfo.

struct MemoryInfo{
    void* pointer;
    size_t size;
    char const* file;
    int line;
    MemoryInfo* next;
    MemoryInfo* before;
};v

Memory allocation

​ When memory allocation occurs, we need to record the informations of it .

​ All of the 5 methods get the informations about size and return the pointer.

​ Thus we can recording the pointer and size over write method.

​ For file name and file line, I create a new class MemAllocate to pass them.

class MemAllocate{
    private:
        char const* file;
        int line;
    public:
        MemAllocate(char const* _file,int _line);
        template <class T> inline T* operator*(T* p);
};

​ During operator* of MemAllocate, it find the suitable node and store the file and size information in it.

Memory free

​ During the return of memory free are all void, also it is no need to record the file and line, we only need to over write and print the message to .log document.

Test case

​ For those 8 methods, we need to test for the basic data type, class without new and class with new.

​ It is correct for basic data type, but wrong for class when use the new and new[].

​ After we check it for several times, we find that the pointer allocations returned is 8 bigger than the pointer returns by malloc in it,thus we can't match it correctly.

​ Instead we check in pointer is weather in the range of the node(pointer~pointer+size).

Memory leak

​ For memory leak, it only need to delete the node when memory free.

​ And at the end of process, print the rest node in double linked list to check the memory leak.

Future direction

• Cause the memory allocation and free is only for data segement, we can try to detect rest segements like heap, stack and code.

Summary

Division of labor

• 王照伟：
• 陈启龙：Detect memory allocation and release in a process and record the memory leak.