Thread: Error: Double free or corruption (out)

Hey all,

I'm having some problems with the following code. I'm implementing a stop-n-wait file transfer protocol and this is the server/file receiver code. It takes in the file size and then one packet at a time, sending back an ACK each time. The code snags at the line indicated and gives the following error. Help?

*** glibc detected *** ./serverUDP: double free or corruption (out): 0x0000000019fa7550 ***
======= Backtrace: =========
/lib64/libc.so.6[0x2b03ed11ad7f]
/lib64/libc.so.6(cfree+0x4b)[0x2b03ed11b1db]
/lib64/libc.so.6(fclose+0x14b)[0x2b03ed1097cb]
/opt/gcc-4.3.4/lib64/libstdc++.so.6(_ZNSt12__basic_fileIcE5closeEv+0x68 )[0x2b03ec9c8658]
/opt/gcc-4.3.4/lib64/libstdc++.so.6(_ZNSt13basic_filebufIcSt11char_trai tsIcEE5closeEv+0xb7)[0x2b03ec976c47]
/opt/gcc-4.3.4/lib64/libstdc++.so.6(_ZNSt14basic_ofstreamIcSt11char_tra itsIcEE5closeEv+0xd)[0x2b03ec97809d]
./serverUDP[0x4026bc]
/lib64/libc.so.6(__libc_start_main+0xf4)[0x2b03ed0c7994]
./serverUDP(__gxx_personality_v0+0xc1)[0x401da9]
======= Memory map: ========
00400000-00407000 r-xp 00000000 00:1b 947937269 /USERS/STUDENTS/F-K/K/KIESERJW/Documents/College/08 Spring 12/CS 462/ftpLab/serverUDP
00607000-00608000 rw-p 00007000 00:1b 947937269 /USERS/STUDENTS/F-K/K/KIESERJW/Documents/College/08 Spring 12/CS 462/ftpLab/serverUDP
19fa7000-19fc8000 rw-p 19fa7000 00:00 0 [heap]
2b03ec6ec000-2b03ec708000 r-xp 00000000 08:01 520726 /lib64/ld-2.5.so
2b03ec708000-2b03ec70b000 rw-p 2b03ec708000 00:00 0
2b03ec908000-2b03ec909000 r--p 0001c000 08:01 520726 /lib64/ld-2.5.so
2b03ec909000-2b03ec90a000 rw-p 0001d000 08:01 520726 /lib64/ld-2.5.so
2b03ec90a000-2b03ec9f5000 r-xp 00000000 08:01 2701812 /opt/gcc-4.3.4/lib64/libstdc++.so.6.0.10
2b03ec9f5000-2b03ecbf4000 ---p 000eb000 08:01 2701812 /opt/gcc-4.3.4/lib64/libstdc++.so.6.0.10
2b03ecbf4000-2b03ecbfb000 r--p 000ea000 08:01 2701812 /opt/gcc-4.3.4/lib64/libstdc++.so.6.0.10
2b03ecbfb000-2b03ecbfd000 rw-p 000f1000 08:01 2701812 /opt/gcc-4.3.4/lib64/libstdc++.so.6.0.10
2b03ecbfd000-2b03ecc10000 rw-p 2b03ecbfd000 00:00 0
2b03ecc10000-2b03ecc92000 r-xp 00000000 08:01 520892 /lib64/libm-2.5.so
2b03ecc92000-2b03ece91000 ---p 00082000 08:01 520892 /lib64/libm-2.5.so
2b03ece91000-2b03ece92000 r--p 00081000 08:01 520892 /lib64/libm-2.5.so
2b03ece92000-2b03ece93000 rw-p 00082000 08:01 520892 /lib64/libm-2.5.so
2b03ece93000-2b03ecea9000 r-xp 00000000 08:01 2701833 /opt/gcc-4.3.4/lib64/libgcc_s.so.1
2b03ecea9000-2b03ed0a8000 ---p 00016000 08:01 2701833 /opt/gcc-4.3.4/lib64/libgcc_s.so.1
2b03ed0a8000-2b03ed0a9000 rw-p 00015000 08:01 2701833 /opt/gcc-4.3.4/lib64/libgcc_s.so.1
2b03ed0a9000-2b03ed0aa000 rw-p 2b03ed0a9000 00:00 0
2b03ed0aa000-2b03ed1f7000 r-xp 00000000 08:01 520717 /lib64/libc-2.5.so
2b03ed1f7000-2b03ed3f7000 ---p 0014d000 08:01 520717 /lib64/libc-2.5.so
2b03ed3f7000-2b03ed3fb000 r--p 0014d000 08:01 520717 /lib64/libc-2.5.so
2b03ed3fb000-2b03ed3fc000 rw-p 00151000 08:01 520717 /lib64/libc-2.5.so
2b03ed3fc000-2b03ed403000 rw-p 2b03ed3fc000 00:00 0
7fff1d6a0000-7fff1d6b5000 rw-p 7ffffffe9000 00:00 0 [stack]
7fff1d7fd000-7fff1d800000 r-xp 7fff1d7fd000 00:00 0 [vdso]
ffffffffff600000-ffffffffffe00000 ---p 00000000 00:00 0 [vsyscall]
Abort

Code:

#include "PracticalSocket.h" // For UDPSocket and SocketException
#include "CCRC32.H"
#include "common.h"
#include <iostream>          // For cout and cerr
#include <cstdlib>           // For atoi()
#include <fstream> 
#include <cmath> 


const int BUFMAX = 255;     // Longest string to echo

int main(int argc, char *argv[]) {

    if (argc != 2) {                  // Test for correct number of parameters
        cerr << "Usage: " << argv[0] << " <Server Port>" << endl;
        exit(1);
    }
    cout << "Server running...\n";
    
    srand ( time(NULL) );
    
    CCRC32* MyCRC32 = new CCRC32();
    MyCRC32->Initialize();
    unsigned short echoServPort = atoi(argv[1]);     // First arg:  local port

    try {
        UDPSocket sock(echoServPort);                
        int recvMsgSize;
        int size;
        int maxSeq = 2;
        int seqNum = 0;
        int numBytes = ((int)((log(maxSeq)/log(2))/8))+1;
        int payloadSize = BUFMAX-numBytes-2;
        
        unsigned char * ack = new unsigned char [numBytes];
        unsigned char *memblock = new unsigned char [BUFMAX];
        
        string sourceAddress;             // Address of datagram source
        unsigned short sourcePort;        // Port of datagram source
        
        ofstream file;
        file.open("test1.out", ios::out|ios::binary);
        if (file.is_open()&& file.good())
        {    
            
            unsigned char* fileSizeArray = new unsigned char[8];
            int fileSize = 0;
            sock.recvFrom(fileSizeArray, 8, sourceAddress, sourcePort);
            printUInts(fileSizeArray,8,"fileSizeArray");
            for (int j = 0;j<8;j++){
                fileSize |= fileSizeArray[j] << 8*j;
            }
            delete [] fileSizeArray;
            cout << "fileSize: " << fileSize<<endl;
            while (true){
                memset(memblock,0,BUFMAX);
                memset(ack,0,numBytes);
                size = 0;
                recvMsgSize = 0;
                while  (size < BUFMAX) { 
                    // Block until receive message from a client
                    recvMsgSize = sock.recvFrom(memblock+size, BUFMAX, sourceAddress, sourcePort);
                    size += recvMsgSize;

                }
                int newSeqNum = 0;
                memblock = unpacketize(memblock,BUFMAX,newSeqNum,numBytes,MyCRC32);
                for (int i = 0;i<numBytes;i++){
                    ack[i] = newSeqNum >> 8*i;
                }
                if (newSeqNum == seqNum){
                    
                    if (fileSize <= payloadSize){
                        //cout << "last write\n";
                        printUInts(memblock+fileSize-16,16, "Last data");
                        cout << "file write output: "<< (file.write ((char*)memblock, fileSize))<<endl;
                        seqNum = maxSeq;
                        fileSize = 0;
                        cout << "COMPLETE TO LINE: " << __LINE__ <<endl;
                        if (file.is_open()){
                            file.close();   //errors out here
                        }                      
                        cout << "COMPLETE TO LINE: " << __LINE__ <<endl;
                    }else{
                        //printUInts(memblock,payloadSize, "data");
                        cout << "file write output: "<< (file.write((char*)memblock, payloadSize)) << endl;
                        fileSize-=payloadSize;
                    }
                    seqNum++;
                    if (seqNum==maxSeq){
                        seqNum = 0;
                    }
                    sock.sendTo(ack, numBytes, sourceAddress, sourcePort);
                }
            }
            
            
            // NOT REACHED
        }else {cout << "Unable to open file";
        }
    } catch (SocketException &e) {
        cerr << e.what() << endl;
        exit(1);
    }
    
    

    return 0;
}