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EXC_BAD_ACCESS When calling the malloc function

I have the following function, but sometimes it fails on malloc, and I don’t know the reason, I thought it could be due to lack of heap size, but I controlled the heap and I realized that I have enough free space for memory allocation when malloc fails, can anyone suggest anything for me

char *substr(const char *pstr, int start, int numchars)
{
 char *pnew;
 pnew=malloc(numchars+1);  //this line fails
 if (pnew==0)
 {
  free(pnew);
  pnew=malloc(numchars+1);
 }


 strncpy(pnew, pstr + start, numchars);
 pnew[numchars] = '\0';
 return pnew;

}

int32 SendData (char * dataBuffer, int CommandType) {struct sockaddr_in remoteServerAddr; int tcpSocket; int errorCode; int counter; int PacketsToSend; int32 ret; char msgbuf [16]; char * package; char * cmdIRes; char RecPacket [BUF_SIZE]; div_t divresult;

counter = 0;
/* Specify struct sock address */
memset(&remoteServerAddr, 0, sizeof(remoteServerAddr));
remoteServerAddr.sin_len = sizeof(remoteServerAddr);
remoteServerAddr.sin_family = AF_INET;
remoteServerAddr.sin_port = htons(11000); // Net byte order required
remoteServerAddr.sin_addr.s_addr = inet_addr("10.252.85.26");

/* Create an TCP socket */
tcpSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (tcpSocket != -1)
{
    /* Connect to server */
    errorCode = connect(tcpSocket, (struct sockaddr*) &remoteServerAddr,
            sizeof(remoteServerAddr));
    if (errorCode == -1)
    {
        /* Connection failed */
        errorCode = socketerror();
        sprintf(msgbuf, "Error %d", errorCode);
        displayMsg("connect:", "Failed!!!", msgbuf, NULL, 0x0100FFFF);
    }
    else
    {
        /* Send packets */
        divresult=div(sizeof(dataBuffer), BUF_SIZE);
        PacketsToSend=divresult.quot;
        if (divresult.rem>0)
        {
            PacketsToSend=PacketsToSend+1;
        }

        while (counter < PacketsToSend)
        {

            packet= substr(dataBuffer, counter*BUF_SIZE, BUF_SIZE);
            errorCode = send(tcpSocket, packet,strlen(packet) , 0);
            if (errorCode == -1)
            {
                errorCode = socketerror();
                sprintf(msgbuf, "Error %d", errorCode);
                displayMsg("send:", "Failed!!!", msgbuf, NULL, 0x0100FFFF);
                break;
            }
            counter++;
        }
        memset(RecPacket, 0, BUF_SIZE);
        errorCode = recv(tcpSocket, RecPacket, BUF_SIZE,0);
        if (errorCode == -1)
        {
            errorCode = socketerror();
        }

        switch (CommandType)
        {
        case CommandType_SendOneTrans:
        case CommandType_SendOfflineData:
            cmdIRes=substr(RecPacket, 14, 10);
            ret= atoi(cmdIRes);
            break;

        case CommandType_TransConfirm:
            cmdIRes=substr(RecPacket, 11, 2);
            if (strcmp(cmdIRes, "ok")==0)
            {
                ret= 1;
            }
            else
            {
                ret= 0;
            }
            break;
        case CommandType_VoucherList:
            SaveVoucherList(RecPacket);
            ret= 1;
            break;

        case CommandType_Identify:
            cmdIRes= substr(RecPacket, 7, 2);
            if (strcmp(cmdIRes, "ok")==0)
            {
                ret=1;
            }
            else
            {
                ret= 0;
            }
            break;

        default:
            break;
        }



    }
    /* Close the socket */
    close(tcpSocket);
    free(RecPacket);
    free(cmdIRes);
    free(packet);
    free(msgbuf);
    return ret;
}
else
{
    errorCode = socketerror();
    sprintf(msgbuf, "Error %d", errorCode);
    displayMsg("socket:", "Failed!!!", msgbuf, NULL, 0x0100FFFF);
}
return (errorCode);

}

uint32 SendOneTrans (fin trans) {   int retVal = 0;   int ret = 0;   int retValCon = 0;    char msg [100];   char * voucherId;   char * ;   char * TerminalNo;   char * isOnline;   char * ReturnedId;   TerminalNo = (12);   voucherId = (4);    = (7);   isOnline = (1);   ReturnedId = (3);

memset(TerminalNo, 0, sizeof(TerminalNo));
strcpy(TerminalNo, (char *)getTerminalNo());

memset(msg, 0, sizeof(msg));
if (trans.success==0)
{

    memset(msg, 0, sizeof(msg));
    memset(voucherId, 0, sizeof(voucherId));
    sprintf(voucherId, "%d", trans.voucherId);
    memset(Amount, 0, sizeof(Amount));
    sprintf(Amount, "%d", trans.Amount);

    memset(isOnline, 0, sizeof(isOnline));
    sprintf(isOnline, "%d", trans.isOnline);

    strcpy(msg, "<Req_fin>");
    strcat(msg, TerminalNo);
    strcat(msg, ",");
    strcat(msg, voucherId);
    strcat(msg, ",");
    strcat(msg, trans.cardNo);
    strcat(msg, ",");
    strcat(msg, Amount);
    strcat(msg, ",");
    strcat(msg, trans.dateOf);
    strcat(msg, ",");
    strcat(msg, trans.TimeOf);
    strcat(msg, ",1");
    strcat(msg, "<EOF>");
    retVal= SendData(msg, CommandType_SendOneTrans);

    if (retVal>=1)
    {
        sprintf(ReturnedId, "%i", retVal);
        memset(msg, 0, sizeof(msg));
        strcpy(msg, "<Req_fin_c>");
        strcat(msg, TerminalNo);
        strcat(msg, ",");

        strcat(msg, ReturnedId);
        strcat(msg, "<EOF>");
        trans.success=1;
        retValCon= SendData(msg, CommandType_TransConfirm);
        if (retValCon!=0)
        {
            trans.success=1;
            ret=1;
        }
    }

    free(msg);
    free(TerminalNo);
    free(Amount);
    free(voucherId);
    return ret;
    //free(ReturnedId);
}

}

+3
5

Apple, EXC_BAD_ACCESS malloc, Google. Apple :

. , . , , , .

+2

: EXC_BAD_ACCESS , . -

*** malloc [705]: 0 × 8c5b00: - , , ; func_name.

? Guard Malloc? , , , , :

malloc(), vm- . , . , () 'd, vm vm, , (), . , !

+2
char *substr(const char *pstr, int start, int numchars)
{
 char *pnew;
 pnew=malloc(numchars+1);  //this line fails

, ? malloc , , , ? null

 if (pnew==0)   
 {
  free(pnew);
  pnew=malloc(numchars+1);
 }

, - , , , , pstr NULL numchars > 0

+1

, malloc - , , malloc - valgrind , .

0
source

This slander helps to understand things:

You will get EXC_BAD_ACCESS in 3 cases:

   1. An object is not initialized
   2. An object is already released
   3. Something else that is not very likely to happen

Therefore, please evaluate the state of other variables in the function or you can insert the call function here to get better solutions.

EDIT: The code continued after receiving information from the comments.

NULL checking is prevented intentionally.

char a[][100] = {"<Req_fin>1","<Req_fin>1","<Req_fin>1<EOF>","<Req_fin>1<EOF>","<Req_fin>1","<Req_fin>1<EOF>","<Req_fin>1<EOF>","<Req_fin>1<EOF>","<Req_fin>1","<Req_fin>1<EOF>"};
char *b= "<EOF>";
char *substr(char *buff,int start,int bytes)
{
char *ptr;

ptr = malloc(bytes+1);
strncpy(ptr,buff+start,bytes);
ptr[bytes]='\0';
return ptr;
}
int main()
{
char buff[100];
int i;
char *ptr;
strcpy(buff,"Abcdef");
for(i=0;i<10;i++)
{
ptr = substr(buff,0,512);
printf("String is %s \n",ptr);
memset(buff,0,sizeof(buff));
strcpy(buff,a[i]);
strcat(buff,b);
 free(ptr);
}
return 0;
}

The above code is working fine. Therefore, please use this as a link if you cannot insert your function here. I can’t just guess the error.

-1
source

Source: https://habr.com/ru/post/1756508/

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