memory leaks
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  1. #1
    Join Date
    Dec 2009
    Posts
    161

    memory leaks

    Hi,

    do you think the following code could lead to memory leaks?

    Code:
    #define _CRT_SECURE_NO_WARNINGS
    #include <windows.h>
    #include <vector>
    #include <cstdlib>
    #include <ctime>
    #include <cstdio>
    #include <boost/circular_buffer.hpp>
    using namespace std;
    using namespace boost;
    
    char * getDateTime(void);
    const short numbuff = 5;
    const short buflen  = 30;
    
    typedef struct
    {
    	unsigned char * pData;
    	unsigned short bufferLength;
    	unsigned short bytesRecorded;
    	bool flag;
    } Buffer;
    
    int main()
    {
    	circular_buffer<Buffer*> cb(numbuff);
    	circular_buffer<Buffer*>::const_iterator it;
    
    	// fill buffer
    	for(int i = 0; i<numbuff; i++)
    	{
    		// set up buffer
    		Buffer *buff       = new Buffer;
    		ZeroMemory(buff, sizeof(Buffer));
    
    		buff->bufferLength  = buflen;
    		buff->bytesRecorded = buflen;
    		buff->flag          = true;
    		buff->pData         = new unsigned char[buflen];
    		buff->pData         = reinterpret_cast<unsigned char *>(getDateTime());
    
    		// push buffer
    		cb.push_back(buff);
    
    		Sleep(1000);
    	}
    
    	// show elements
    
    	for(int i = 0; i<(int)cb.size(); i++)
    	{
    		printf("%s\n", cb[i]->pData);
    	}
    
    	system("pause");
    	return EXIT_SUCCESS;
    }
    
    // getDateTime (Fri, 10 Oct 2008 14:41:59 GMT)
    char * getDateTime(void)
    {
    	time_t rawtime;
    	struct tm * timeinfo;
    	time(&rawtime);
    	timeinfo = gmtime(&rawtime);
    	char * buffer = new char[30];
    	strftime(buffer,30,"%a, %d %b %Y %X GMT",timeinfo);
    	return buffer;
    }
    I cannot delete "buff" since its scope is inside the first for loop...

  2. #2
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    Hi,

    do you think the following code could lead to memory leaks? it creates a
    circualr buffer made up of 5 element then it pushes 10 elements (overwriting
    the first 5) when overwriting , do you think the eldest pointed memory will
    be overwritten, or a new pointer in memory will be written?

    Code:
    #define _CRT_SECURE_NO_WARNINGS
    #include <windows.h>
    #include <vector>
    #include <cstdlib>
    #include <ctime>
    #include <cstdio>
    #include <boost/circular_buffer.hpp>
    using namespace std;
    using namespace boost;
    
    char * getDateTime(void);
    const short numbuff = 5;
    const short buflen  = 30;
    
    typedef struct
    {
     unsigned char * pData;
     unsigned short bufferLength;
     unsigned short bytesRecorded;
     bool flag;
    } Buffer;
    
    int main()
    {
     circular_buffer<Buffer*> cb(numbuff);
     circular_buffer<Buffer*>::const_iterator it;
    
     printf("Push elements:\n");
     // fill buffer
     for(int i = 0; i<10; i++)
     {
      // set up buffer
      Buffer *buff       = new Buffer;
      ZeroMemory(buff, sizeof(Buffer));
    
      buff->bufferLength  = buflen;
      buff->bytesRecorded = buflen;
      buff->flag          = true;
      buff->pData         = new unsigned char[buflen];
      buff->pData         = reinterpret_cast<unsigned char *>(getDateTime());
    
      printf("%s\n", buff->pData);
    
      // push buffer
      cb.push_back(buff);
    
      Sleep(1000);
     }
    
     printf("\nShow elements:\n");
    
     // show elements
     for(int i = 0; i<static_cast<int>(cb.size()); i++)
     {
      printf("%s\n", cb[i]->pData);
     }
    
     system("pause");
     return EXIT_SUCCESS;
    }
    
    // getDateTime (Fri, 10 Oct 2008 14:41:59 GMT)
    char * getDateTime(void)
    {
     time_t rawtime;
     struct tm * timeinfo;
     time(&rawtime);
     timeinfo = gmtime(&rawtime);
     char * buffer = new char[30];
     strftime(buffer,30,"%a, %d %b %Y %X GMT",timeinfo);
     return buffer;
    }
    // thanks

  3. #3
    Join Date
    Sep 2004
    Location
    Holland (land of the dope)
    Posts
    4,123

    Re: memory leaks

    buff->pData = new unsigned char[buflen];
    buff->pData = reinterpret_cast<unsigned char *>(getDateTime());
    This leaks. pData is overwritten the 2nd time so the memory you created the 1st time is gone.
    Also... who frees the memory that 'getDateTime' has created.

  4. #4
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    Quote Originally Posted by Skizmo View Post
    This leaks. pData is overwritten the 2nd time so the memory you created the 1st time is gone.
    Also... who frees the memory that 'getDateTime' has created.
    by the way, how can I change getDateTime() to return char[30] ?? I mean the return type...

    thanks

  5. #5
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Location
    Wallisellen (ZH), Switzerland
    Posts
    17,269

    Re: memory leaks

    Quote Originally Posted by THEARTOFWEB View Post
    by the way, how can I change getDateTime() to return char[30] ?? I mean the return type...

    thanks
    For example:
    Code:
     void getDateTime( char *buffer)
    {
     time_t rawtime;
     struct tm * timeinfo;
     time(&rawtime);
     timeinfo = gmtime(&rawtime);
    
     strftime(buffer,30,"%a, %d %b %Y %X GMT",timeinfo);
    }
    Now you can:
    Code:
    char buffer[30];
    getDateTime(buffer);
    Victor Nijegorodov

  6. #6
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Location
    Wallisellen (ZH), Switzerland
    Posts
    17,269

    Re: memory leaks

    All that you newed you *must* delete. Period.
    If you don't delete what you have newed then you produce memory leaks.
    Victor Nijegorodov

  7. #7
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    Quote Originally Posted by VictorN View Post
    All that you newed you *must* delete. Period.
    If you don't delete what you have newed then you produce memory leaks.
    Ok. As I was suggested in this very forum...I am going to use vector to collect chars...is that ok? and no pointers anymore...

  8. #8
    VictorN's Avatar
    VictorN is offline Super Moderator Power Poster
    Join Date
    Jan 2003
    Location
    Wallisellen (ZH), Switzerland
    Posts
    17,269

    Re: memory leaks

    Quote Originally Posted by THEARTOFWEB View Post
    ...I am going to use vector to collect chars...is that ok? and no pointers anymore...
    Yes, it is definetly a very good idea!
    Victor Nijegorodov

  9. #9
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    For instance...do you think the following could be better approach?

    Code:
    struct Buffer
    {
    public:
    	vector<unsigned char> vChar;
    	unsigned int bufferLength;
    	unsigned int bytesRecorded;
    	Buffer() : bytesRecorded(0), bufferLength(0), vChar(NULL) { };
    };
    
    int main()
    {
    	circular_buffer<Buffer> cb(numbuff);
    	circular_buffer<Buffer>::const_iterator it;
    
    	(...)
    }
    thanks

  10. #10
    Join Date
    Feb 2005
    Posts
    2,160

    Re: memory leaks

    No memory leaks that I see, but certainly undefined behavior as your "char szTime" goes out of scope when your for loop finishes.

    Why not declare your "struct Buffer" with a fixed size "payload":

    Code:
    struct Buffer
    {
    public:
    	char payload[30];
    	int bufferLength;
    	int bytesRecorded;
    	int user;
    	Buffer() : bytesRecorded(0), bufferLength(0), user(0), payload(NULL) { };
    };
    Edit: remove the "payload(NULL)" form your constructor too.
    Last edited by hoxsiew; January 25th, 2010 at 01:23 PM. Reason: update

  11. #11
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    Ok, so all I can do is the following:

    Code:
    #include <windows.h>
    #include <vector>
    #include <cstdlib>
    #include <ctime>
    #include <cstdio>
    #include <boost/circular_buffer.hpp>
    using namespace std;
    using namespace boost;
    
    void getDateTime(char * szTime);
    const int numbuff = 3;
    const int buflen  = 30;
    
    struct Buffer
    {
    public:
    	char payload[30];
    	int bufferLength;
    	int bytesRecorded;
    	int user;
    	Buffer() : bufferLength(0), bytesRecorded(0), user(0) { }
    };
    
    int main()
    {
    	circular_buffer<Buffer> cb(numbuff);
    
    	// Insert elements
    	printf("Push elements:\n");
    	for(int i = 0; i<5; i++)
    	{
    		// Get time
    		char szTime[30]; getDateTime(szTime);
    
    		// Init Buff
    		Buffer buff;
    		ZeroMemory(&buff, sizeof(Buffer));
    
    		memcpy((void*)buff.payload, szTime, buflen);
    		buff.user          = i;
    		buff.bufferLength  = buflen;
    		buff.bytesRecorded = buflen;
    
    		cb.push_back(buff);
    
    		printf("%s\n", buff.payload);
    		Sleep(1000);
    	}
    
    	// Show elements:
    	printf("Show elements:\n");
    	for(int i = 0; i<(int)cb.size(); i++)
    	{
    		printf("%s\n", cb[i].payload);
    	}
    
    	system("pause");
    	return EXIT_SUCCESS;
    }
    
    void getDateTime(char * szTime)
    {
    	time_t rawtime = time(NULL);
    	struct tm timeinfo;
    	gmtime_s(&timeinfo, &rawtime);
    	strftime(szTime, 30, "%a, %d %b %Y %X GMT", &timeinfo);
    }
    so I will set payload to contains a loto of chars like:

    Code:
    char payload[4096]
    then if payload is less the 4096 bytes long I will zero fill or read only a part of that

  12. #12
    Join Date
    Jun 2008
    Posts
    592

    Re: memory leaks

    Looks like you aren't taking advantage of c++ at all. this looks like c with classes approach with boost?

    Code:
    #include <windows.h>
    
    #include <ctime>
    #include <string>
    #include <iostream>
    #include <boost/circular_buffer.hpp>
    #include <boost/foreach.hpp>
    
    using namespace std;
    using namespace boost;
    
    string getDateTime()
    {
    	time_t rawtime = time(NULL);
    	tm* timeinfo = gmtime(&rawtime);
    	char szTime[30];
    	strftime(szTime, 30, "%a, %d %b %Y %X GMT", timeinfo);
    	return szTime;
    }
     
    struct Buffer 
    {
    	string payload;
    	int user;
    	Buffer() : payload(), user() { }
    	Buffer( const string& payload, int user ) : payload(payload), user(user) { }
    };
     
    int main()
    {
    	const int numbuff = 3;
    	circular_buffer<Buffer> cb(numbuff);
     
    	// Insert elements
    	cout << "Push elements:" << endl;
     
    	for( int i = 0; i < 5; i++ )
    	{
    		cb.push_back( Buffer( getDateTime(), i ) );
    		Sleep(1000);
    	}
     
    	// Show elements:
    	cout << "Show elements:" << endl;
     
    	BOOST_FOREACH( Buffer Record, cb )
    	cout << Record.payload << endl;
     
    	system("pause");
    	return 0;
    }
    This is more c++ than the c approach , but understanding how and why to use string, constructors, containers and etc will take time. If this isn't what you require, just state what is wrong with the above code.
    0100 0111 0110 1111 0110 0100 0010 0000 0110 1001 0111 0011 0010 0000 0110 0110 0110 1111 0111 0010
    0110 0101 0111 0110 0110 0101 0111 0010 0010 0001 0010 0001 0000 0000 0000 0000
    0000 0000 0000 0000

  13. #13
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    Quote Originally Posted by Joeman View Post
    This is more c++ than the c approach , but understanding how and why to use string, constructors, containers and etc will take time. If this isn't what you require, just state what is wrong with the above code.
    I might deal with /char/ (or unsigned char) data returned by some other functions....

    I know I could cast to char to string...Yet, I'd like to stick with char for the moment

  14. #14
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    I mean, binary string mostly (unsigned char) the getDateTime() is just a way to fill the buffer with something for the moment...in the near future I'll be dealing with binary string only in my application

  15. #15
    Join Date
    Dec 2009
    Posts
    161

    Re: memory leaks

    Quote Originally Posted by Joeman View Post
    This is more c++ than the c approach , but understanding how and why to use string, constructors, containers and etc will take time. If this isn't what you require, just state what is wrong with the above code.
    I think for the moment I'll use this:

    Code:
    #include <windows.h>
    #include <cstdlib>
    #include <ctime>
    #include <cstdio>
    #include <cstring>
    #include <boost/circular_buffer.hpp>
    using namespace std;
    using namespace boost;
    
    void getDateTime(char * szTime);
    const int numbuff = 3;
    const int buflen  = 30;
    
    struct cBuffer
    {
    	char data[1024];
    	int bytesRecorded;
    	bool flag;
    	cBuffer(char * data_, int bytesRecorded_, bool flag_) :
    	bytesRecorded(bytesRecorded_), flag(flag_)
    	{
    		memcpy(static_cast<void *>(data), static_cast<void *>(data_), bytesRecorded);
    	}
    };
    
    
    int main()
    {
    	circular_buffer<cBuffer> cb(numbuff);
    
    	// Insert elements
    	printf("Push elements:\n");
    	for(int i = 0; i < 5; i++)
    	{
    		char szTime[30]; getDateTime(szTime);
    
    		cb.push_back(cBuffer(szTime, 30, true));
    
    		printf("%s\n", szTime);
    
    		Sleep(1000);
    	}
    
    	// Show elements:
    	printf("Show elements:\n");
    	for(int i = 0; i<(int)cb.size(); i++)
    	{
    		printf("%s\n", cb[i].data);
    	}
    
    	system("pause");
    	return EXIT_SUCCESS;
    }
    
    void getDateTime(char * szTime)
    {
    	time_t rawtime = time(NULL);
    	struct tm timeinfo;
    	gmtime_s(&timeinfo, &rawtime);
    	strftime(szTime, 30, "%a, %d %b %Y %X GMT", &timeinfo);
    }
    this time I think I won't be having any memory leaks!

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