Learning to use valgrind for memory Detection

There are three common memory leaks in C/C ++:

1. After malloc and realloc, they forget free; after new, they forget Delete; after new [], they forget Delete [].

2. Use the count method to manage the memory. The two count pointers direct to each other, leading to memory leakage.

3. Place the allocated and used memory in the container.

Among them, the memory leakage method in 3rd also exists in languages such as Java and C # That automatically release the memory.

The following is an example of Memory leakage caused by 2nd cases:

Valgrindmemcheck. cpp

#include <iostream>class A;class B;class A{public:    A()    :b(0),cnt(0)    {}    A(B *pB)    :b(pB),cnt(new int(1))    {}    A(const A &a)    :b(a.b),cnt(a.cnt)    {        ++*cnt;    }    A &operator =(const A &a);    ~A();private:    B *b;    int *cnt;};class B{public:    B()    :a(0),cnt(0)    {}    B(A *pA)    :a(pA),cnt(new int (1))    {}    B(const B &b)    :a(b.a),cnt(b.cnt)    {        ++*cnt;    }    B &operator =(const B &b);    ~B();private:    A *a;    int *cnt;};A &A::operator =(const A &a){    if(this == &a)        return *this;    if(cnt && 0 == --*cnt)    {        delete b;        delete cnt;    }    b = a.b;    cnt = a.cnt;    ++*cnt;    return *this;}A::~A(){    if(cnt && 0 == --*cnt)    {        delete b;        delete cnt;    }}B &B::operator =(const B &b){    if(this == &b)        return *this;    if(cnt && 0 == --*cnt)    {        delete a;        delete cnt;    }    a = b.a;    cnt = b.cnt;    ++*cnt;    return *this;}B::~B(){    if(cnt && 0 == --*cnt)    {        delete a;        delete cnt;    }}void test0(){    A a0;    B b0;    A a1(new B());    B b1(new A());}void test1(){    A *pA = new A();    B *pB = new B();    B b(pA);    A a(pB);}void test2(){    A a;    B b;    a = &b;    b = &a;}int main(void){    test0();    test1();    test2();    return 0;}

Makefile

all:ValgrindMemcheckValgrindMemcheck:ValgrindMemcheck.o        g++ -g -Wall -o $@ $^ValgrindMemcheck.o:ValgrindMemcheck.cpp        g++ -g -Wall -o $@ -c $<.PHONY:clean:        - $(RM) ValgrindMemcheck.cpp        - $(RM) ValgrindMemcheck.o

Which of the following memory leaks in test0, test1, and Test2?

Run:

Valgrind -- leak-check = full./valgrindmemcheck

We will find memory problems in test2.

References:

Http://www.ibm.com/developerworks/cn/linux/l-cn-valgrind/

Several blog posts are recommended:

Http://www.ibm.com/developerworks/cn/linux/l-cn-valgrind/

Http://blog.dccmx.com/2011/01/valgrind-massif/

Http://blog.dccmx.com/2011/01/callgrind/

Http://blog.dccmx.com/2011/01/gprof/

Http://blog.dccmx.com/2011/01/valgrind-memcheck/

Http://eduunix.ccut.edu.cn/

Http://www.oschina.net/project/tag/401/Neural-Network? Lang = 21 & sort = View