Thread: please help on memory allocation

Hi all I have trouble in allocating my memory.
I am not quit sure what's going on there and need your help.
My program is to read a file that was combined of serveral image files(called Wad file)
Each of combined image file has header :

file size: 4 bytes
file name: 28 bytes
buffer

and my code is bellow:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef unsigned int UINT4;
typedef unsigned char UCHAR;
const int file_name_length	= 28;



typedef struct {
  UINT4 file_size;
  char file_name[file_name_length];
  UCHAR *file_buffer;
  
} WAD;   //struture of file

WAD *WadPtr; // poter of struture
int file_count;

static void readWAD(char *filename) {

	int count =0,i, j=0;
	FILE *fp, *out;

   if (!(fp=fopen(filename,"rb")))     //read file
	{
		printf ("check your ass bud!\n");
		exit(1);
	}

	if (!(out=fopen("report","wb")))    //test 
	{
		printf ("check your ass bud!\n");
		exit(1);
	}

	while(!feof(fp)){
		WadPtr = (WAD*)realloc(WadPtr, sizeof(WAD)* (j+1));        // reallocate poniter every one image
		fread((UINT4* )&WadPtr[count].file_size, sizeof(UINT4), 1, fp);  // read file size
		printf("File size %d: ", WadPtr[count].file_size);
		if(WadPtr[count].file_size < 0) {
		printf ("syzstem freaking out\n!");
		exit(1);
		}	
		fread((char* )WadPtr[count].file_name, sizeof(char), file_name_length, fp); // read file name
		printf("  %s \n", WadPtr[count].file_name);
	

		WadPtr[count].file_buffer = (UCHAR *)malloc(sizeof(UCHAR)*WadPtr[count].file_size);   // read buffer
		// problem is here....how should i deal with memory here?

		fread((void *)WadPtr[count].file_buffer, sizeof(UCHAR), WadPtr[count].file_size, fp);
		
		count++;
		j++;
		
	}
	fwrite((void *)WadPtr[count].file_buffer, sizeof(UCHAR), WadPtr[count].file_size, out);
	free(WadPtr);

	 if(fp != stdin)
	   fclose(fp);
	 fclose(out);
     file_count=count;
} 

int main (int argc, char *argv[])
{
	
	if (argc != 2)
    {
      printf ("Usage: %s <File name> \n", argv[0]);
      exit (1);
    }

	printf ("argv[1]: %s  \n", argv[1]);	
    readWAD(argv[1]);

}

and system crashed when loop is finish
can anyone help me please!

Originally Posted by acfror

WadPtr[count].file_buffer = (UCHAR *)malloc(sizeof(UCHAR)*WadPtr[count].file_size); // read buffer
// problem is here....how should i deal with memory here?

fread((void *)WadPtr[count].file_buffer, sizeof(UCHAR), WadPtr[count].file_size, fp);

You are casting malloc to UCHAR*.then you are using it to read in binary.read faq

The first parameter to realloc() is a pointer that was previously returned by malloc(), calloc(), realloc() or a NULL pointer. What is the value of WadPtr the first time that function is entered? I don't see where WadPtr was ever initialized to anything, including NULL.

Second point: WadPtr is being freed before the function ends. So why is it a global variable? It should be local to that function.

Third: make readWAD() return an int (the record count) instead of using a global file_count variable. Whatever function calls readWAD() can easily grab the file count that way.

Originally Posted by Ancient Dragon

The first parameter to realloc() is a pointer that was previously returned by malloc(), calloc(), realloc() or a NULL pointer. What is the value of WadPtr the first time that function is entered? I don't see where WadPtr was ever initialized to anything, including NULL.

WadPtr is declared outside of any function, so it is of static storage duration, it's initialised to a NULL pointer on startup.