Question

What is wrong with strcpy() in this code?

void process_filedata(char *filename)
{
  void* content;
  const char * buffer;
  char * temp;
  char * row;
  char * col;
  int lsize,buflen,tmp,num_scan; //num_scan - number of characters scanned
  int m=0,p=0,d=0,j=0; //m - machine, p - phase, d- delimiter, j - job

  FILE *file_pointer = fopen("machinetimesnew.csv","r");

  if(file_pointer == NULL)
  {
   error_flag =  print_error("Error opening file");

   if(error_flag) exit(1);
  }
  fseek(file_pointer, 0 ,SEEK_END);
  lsize = ftell(file_pointer);
  buflen = lsize;
  rewind(file_pointer);
 // content = (char*) malloc(sizeof(char)*lsize);
  fread(content,1,lsize,file_pointer);
  buffer = (const char*) content;
  strcpy(temp,buffer);
  row = strtok(temp,"\n");
  ...............
  ...............

I am getting a segmentation fault..

Answer 1

There are actually three segmentation faults here:

fread(content,1,lsize,file_pointer);
strcpy(temp,buffer);
row = strtok(temp,"\n");

The first one is fread() which is attempting to write to memory that does not yet exist as far as your process is concerned.

The second one is strcpy(), (expounding on the first) you are attempting to copy to a pointer that points to nothing. No memory (other than the pointer reference itself) has been allocated for temp, statically or dynamically.

Fix this via changing temp to look like this (allocating it statically):

char temp[1024];

Or use malloc() to dynamically allocate memory for it (as well as your other pointers, so they actually point to something), likewise for content. If you know the needed buffer size at compile time, use static allocation. If not, use malloc(). ‘Knowing’ is the subject of another question.

The third one is strtok() , which is going to modify temp en situ (in place), which it obviously can not do, since temp was never allocated. In any event, don’t expect temp to be the same once strtok() is done with it. By the name of the variable, I assume you know that.

Also, Initializing a pointer is not the same thing as allocating memory for it:

char *temp = NULL; // temp is initialized
char *temp = (char *) malloc(size); // temp is allocated if malloc returns agreeably, cast return to not break c++

Finally, please get in the habit of using strncpy() over strcpy(), its much safer.