segfault on realloc

[ziel]

Hi everyone,

i hope someone could run over my code to see what im doing wrong...

this is not the total code but enough to see the problem.. i hope..

i have a function which reads from a socket and and dynamicly manages memory for a buffer. This buffer is first allocated in the main method. the problem is that i get a segfault sometimes in the realloc function in the main method just after "before realloc in entry ... " and sometimes in the strcat function To my knowledge is this buffer always big enough to contain the string
hope someone can help me...

my code looks like this..

# define BUFFER  1024
static xmlString = NULL;
static _2k =2

main(){

/* if pointer points to other than null than this service has been called before so reset and reuse it */ 
_2k = 2; 

if (xmlString != NULL ){ 
 deb_log(0, "%s", "before: realloc in entry"); 
 ptr = (void * )realloc(xmlString, (_2k * RS_BUFFER)); 
 if ( ptr == NULL ){ 
 realloc(xmlString, 0 ); 
 return MALLOC_ERROR + MV + "Error while allocating memory"; 
} 
xmlString = ptr; 

deb_log(0, "%s", "after: realloc in entry"); 
memset(xmlString, 0, (_2k * RS_BUFFER)); 
deb_log(0, "%s", "after: memset"); 


receiveHttpMsg(&xmlString, fd );

} 

int receiveHttpMsg(char ** buf, int fd){ 

int  totalBytesRcvd; 
void * tmp; 
char * readBuffer = (char * ) calloc(1, BUFFER); 
int bytesRcvd = 1; /* Bytes read in single recv() */ 

/* Receive response from the server */ 
printf("Received: "); 
while (bytesRcvd > 0) { 

 /* Receive up to the buffer size (minus 1 to leave space for 
 a null terminator) did this in loop because otherwise the whole message could not be read 
 */ 
  if ((bytesRcvd = recv(fd, readBuffer, (BUFFER -1) , 0)) > 0){ 
  totalBytesRcvd += bytesRcvd; /* total bytes read in loop*/ 
  readBuffer[bytesRcvd] = '\0'; 
  printf(" [%d][%d][%d]\n", strlen(*buf), strlen(readBuffer), _2k * RS_BUFFER); 
    
    if ( (strlen(*buf) +strlen(readBuffer) -1) > _2k * RS_BUFFER){ 
     _2k++; 
     tmp = (void * )realloc(*buf, (_2k * RS_BUFFER)); 
  
    if ( tmp == NULL ){ 
     printf("error while reallocating .. \n"); 
     realloc(*buf, 0 ); 
     free(readBuffer); 
     return -1; 
    } 
   
   *buf = tmp; 
   (*buf)[totalBytesRcvd]= '\0'; 
   printf(" buffer enlarged [%d]\n", strlen(*buf)); 
   } 
   
   /* STRCAT SEGFAULT*/
   deb_log(0, "%s", "tocopy"); 
   strcat(*buf, readBuffer); 
   deb_log(0, "%s", "copy--done"); 

/* memset(readBuffer, 0 , BUFFER); */ 

  } 
/* host closed connection so we cleanup socket */ 
else{ 
printf("close connection \n"); 
close(fd); 
free(readBuffer); 
break; 
} /* end else */

}  /* end while */



}

[quzah]

static xmlString = NULL;
static _2k =2

How about you actually provide a type for your variables?

Quzah.

[ziel]

could someone give me a real answer please ?

of course i declared..

static char * xmlString = NULL;
static int _2k = 2;

[The Dog]

If you want a "real" answer, then post some "real" code please.

[Shiro]

Hope this answer is real enough.

The function realloc() deallocates the old pointer. This means that after realloc() xmlString == NULL. So you can not reallocate it. If you want to be sure it is NULL, then add a check. If it is not NULL, then use free() to free the still allocated memory.

[Hammer]

What is this:
>>return MALLOC_ERROR + MV + "Error while allocating memory";