I'm trying to read a binary file that has blocks starting with an identifier (like a 3DS file). I loop through the file and using a switch the program determines what identifier a block has and then reads the data into the file struct. Sometimes I need to use malloc to allocate memory for dynamic sized data. While reading, the switch often goes through the same case wherin memory is allocated, but at a specific point in the file it crashes on that same malloc. The file that I want to read is about 1MB. But when I try the program with another file of about 10kB and the same structure, it reads it succesfully.
What could be causing this problem?
The error code that I get when debugging is:
Heap corruption detected at 0441F080
HEAP[prog.exe]: HEAP: Free Heap block 441f078 modified at 441f088 after it was freed
Also when I execute it in debug mode, for some reason I can read more data from the file. The program lives longer before it crashes.
Here is the code piece where it crashes:
switch (id) {
case 0x62:
case 0x63:
// ...
{
char n_vertices = id - 0x60 + 1;// just how I calculate the n_vertices from the block ID
fread(&mem.blocks[i].data.attr_6n.height, 2, 1, f);
mem.blocks[i].data.attr_6n.vertices = malloc(2 * n_vertices);// crash
for (short k = 0; k < n_vertices; k++) {
fread(&mem.blocks[i].data.attr_6n.vertices[k], 2, 1, f);// read shorts
}
}
break;
// ...
}
