Program using read() entering into an infinite loop
- by Soham
1oid ReadBinary(char *infile,HXmap* AssetMap)
{
int fd;
size_t bytes_read, bytes_expected = 100000000*sizeof(char);
char *data;
if ((fd = open(infile,O_RDONLY)) < 0)
err(EX_NOINPUT, "%s", infile);
if ((data = malloc(bytes_expected)) == NULL)
err(EX_OSERR, "data malloc");
bytes_read = read(fd, data, bytes_expected);
if (bytes_read != bytes_expected)
printf("Read only %d of %d bytes %d\n", \
bytes_read, bytes_expected,EX_DATAERR);
/* ... operate on data ... */
printf("\n");
int i=0;
int counter=0;
char ch=data[0];
char message[512];
Message* newMessage;
while(i!=bytes_read)
{
while(ch!='\n')
{
message[counter]=ch;
i++;
counter++;
ch =data[i];
}
message[counter]='\n';
message[counter+1]='\0';
//---------------------------------------------------
newMessage = (Message*)parser(message);
MessageProcess(newMessage,AssetMap);
//--------------------------------------------------
//printf("idNUM %e\n",newMessage->idNum);
free(newMessage);
i++;
counter=0;
ch =data[i];
}
free(data);
}
Here, I have allocated 100MB of data with malloc, and passed a file big enough(not 500MB) size of 926KB about. When I pass small files, it reads and exits like a charm, but when I pass a big enough file, the program executes till some point after which it just hangs. I suspect it either entered an infinite loop, or there is memory leak.
EDIT For better understanding I stripped away all unnecessary function calls, and checked what happens, when given a large file as input. I have attached the modified code
void ReadBinary(char *infile,HXmap* AssetMap)
{
int fd;
size_t bytes_read, bytes_expected = 500000000*sizeof(char);
char *data;
if ((fd = open(infile,O_RDONLY)) < 0)
err(EX_NOINPUT, "%s", infile);
if ((data = malloc(bytes_expected)) == NULL)
err(EX_OSERR, "data malloc");
bytes_read = read(fd, data, bytes_expected);
if (bytes_read != bytes_expected)
printf("Read only %d of %d bytes %d\n", \
bytes_read, bytes_expected,EX_DATAERR);
/* ... operate on data ... */
printf("\n");
int i=0;
int counter=0;
char ch=data[0];
char message[512];
while(i<=bytes_read)
{
while(ch!='\n')
{
message[counter]=ch;
i++;
counter++;
ch =data[i];
}
message[counter]='\n';
message[counter+1]='\0';
i++;
printf("idNUM \n");
counter=0;
ch =data[i];
}
free(data);
}
What looks like is, it prints a whole lot of idNUM's and then poof segmentation fault
I think this is an interesting behaviour, and to me it looks like there is some problem with memory
FURTHER EDIT I changed back the i!=bytes_read it gives no segmentation fault. When I check for i<=bytes_read it blows past the limits in the innerloop.(courtesy gdb)
