Debug Error - abort() has been called (gcz2tga) - c++

Question

Complete C++/C newbie here. I recompiled gcz2tga (I did not make this code, just found it on the webs) into a debug .exe file using Visual Studio 2019. Everything works well until it gets to "split_images" and then the program spits out this error:
Debug Error!
Program: C:\Users\Harrison\source\repos\gcz2tga\Debug\gcz2tga.exe
abort() has been called
(Press Retry to debug the application)
When I hit Retry, the program closes. The code is set up like this:
/* gcz2tga.c: Slice up a directory full of GCZ (texture) files into TGA files.
*
* Credit goes to afwefwe for reverse-engineering the texture format
* and LZSS compression */
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
/* Assuming x86, usual endian crap is not accounted for */
typedef unsigned char u8_t;
typedef unsigned short u16_t;
typedef unsigned int u32_t;
struct image
{
unsigned int width, height;
u8_t *planes;
};
struct clip
{
short x, y, w, h;
};
static u16_t swab16(u16_t in)
{
/* GC headers are big-endian */
return ((in & 0xFF) << 8) | (in >> 8);
}
static void unpack_gc(struct image *out, u8_t *in, size_t out_sz)
{
unsigned int npixels;
unsigned int i;
unsigned int j;
u16_t *pixels;
u16_t *pheight;
u16_t *pwidth;
u16_t *pmagic;
u16_t pixel;
pmagic = (u16_t *) in;
pheight = (u16_t *) (in + 14);
pwidth = (u16_t *) (in + 12);
if (*pmagic != 0x4347) {
fprintf(stderr, "(FAIL: Invalid header)\n");
exit(EXIT_FAILURE);
}
/* Set up output image struct */
in += 24;
out->width = swab16(*pwidth);
out->height = swab16(*pheight);
out->planes = malloc(out->width * out->height * 4);
/* Clamp W/H (don't know why this is necessary but it is) */
out->width = out->width > 1024 ? 1024 : out->width;
out->height = out->height > 1024 ? 1024 : out->height;
fprintf(stderr, "(%dx%d)", out->width, out->height);
/* Unpack pixels */
pixels = (u16_t *) in;
npixels = out->width * out->height;
if (out_sz > npixels * 4) {
/* Deep image (i.e. 32-bit) */
memcpy(out->planes, pixels, npixels * 4);
} else {
/* Shallow image (i.e. 16-bit) */
for (i = 0, j = 0 ; i < npixels ; i++) {
pixel = pixels[i];
out->planes[j++] = ((pixel ) & 0x1F) << 3; /* B */
out->planes[j++] = ((pixel >> 5) & 0x1F) << 3; /* G */
out->planes[j++] = ((pixel >> 10) ) << 3; /* R */
out->planes[j++] = pixel & 0x8000 ? 0xFF : 0x00; /* A */
}
}
}
static u8_t *expand_lzss(u8_t *lzss, size_t *pout_sz)
{
static u8_t ring[0x1000];
unsigned int ring_pos = 0x0FEE;
unsigned int chunk_offset;
unsigned int chunk_length;
u32_t control_word = 1;
size_t length;
u8_t cmd1;
u8_t cmd2;
u8_t *out;
u8_t *pos;
u8_t *in;
/* Header = 32 bit unpacked file length */
length = *((u32_t *) lzss);
*pout_sz = length;
if (length > 8000000) {
fprintf(stderr, "(FAIL: Unreasonably large expanded size %d)\n",
length);
exit(EXIT_FAILURE);
}
out = malloc(length * 2); /* Seems to overrun */
pos = out;
in = lzss + 4;
while (length > 0) {
if (control_word == 1) {
/* Read a control byte */
control_word = 0x100 | *in++;
}
/* Decode a byte according to the current control byte bit */
if (control_word & 1) {
/* Straight copy */
*pos++ = *in;
ring[ring_pos] = *in++;
ring_pos = (ring_pos + 1) % 0x1000;
length--;
} else {
/* Reference to data in ring buffer */
cmd1 = *in++;
cmd2 = *in++;
chunk_length = (cmd2 & 0x0F) + 3;
chunk_offset = ((cmd2 & 0xF0) << 4) | cmd1;
for ( ; chunk_length > 0 ; chunk_length--) {
/* Copy historical data to output AND current ring pos */
*pos++ = ring[chunk_offset];
ring[ring_pos] = ring[chunk_offset];
/* Update counters */
chunk_offset = (chunk_offset + 1) % 0x1000;
ring_pos = (ring_pos + 1) % 0x1000;
length--;
}
}
/* Get next control bit */
control_word >>= 1;
}
return out;
}
static void readfile(const char *filename, u8_t **data, long *nbytes)
{
FILE *f;
f = fopen(filename, "rb");
if (f == NULL) abort();
fseek(f, 0, SEEK_END);
*nbytes = ftell(f);
fseek(f, 0, SEEK_SET);
*data = malloc(*nbytes);
fread(*data, *nbytes, 1, f);
fclose(f);
}
void put8(FILE *f, unsigned char val)
{
fwrite(&val, 1, 1, f);
}
void put16(FILE *f, unsigned short val)
{
fwrite(&val, 2, 1, f);
}
void split_images(const char *in_dir, const char *out_dir,
struct image *images, int nimages)
{
struct clip *clips;
char filename[512];
long nbytes;
u8_t *data;
char *name;
FILE *f;
int i;
int j;
int k;
/* Read file and get TOC */
sprintf(filename, "%s/system.idx", in_dir);
readfile(filename, &data, &nbytes);
clips = (struct clip *) (data + 0x01BC);
name = (char *) (data + 8 + *((long *) data));
/* Guess how many clips there are with a heuristic */
for (i = 0 ; clips[i].w != 0 && clips[i].h != 0 ; i++) {
sprintf(filename, "%s/%s.tga", out_dir, name);
name += strlen(name) + 3;
f = fopen(filename, "wb");
if (f == NULL) abort();
/* Locate the correct source image */
j = 0;
while (clips[i].y > images[j].height) {
clips[i].y -= images[j].height;
j++;
}
/* Write header */
put8(f, 0); put8(f, 0); put8(f, 2);
put16(f, 0); put16(f, 0); put8(f, 0);
put16(f, 0); put16(f, 0); put16(f, clips[i].w); put16(f, clips[i].h);
put8(f, 32); put8(f, 32);
/* Write scanlines */
for (k = 0 ; k < clips[i].h ; k++) {
if (clips[i].y == images[j].height) {
clips[i].y = 0;
j++;
}
fwrite(images[j].planes + ((images[j].width * clips[i].y) +
clips[i].x) * 4, clips[i].w, 4, f);
clips[i].y++;
}
/* Close output file */
fclose(f);
}
/* Cleanup */
free(data);
}
int main(int argc, char **argv)
{
char *in_dir;
char *out_dir;
struct image images[32];
char filename[256];
unsigned int i;
long filesize;
u8_t *lzss, *gc;
size_t out_sz;
FILE *f;
/* Usage */
if (argc != 3) {
fprintf(stderr, "Usage: %s [indir] [outdir]\n", argv[0]);
return EXIT_FAILURE;
}
/* Setup */
memset(images, 0, sizeof(images));
in_dir = argv[1];
out_dir = argv[2];
for (i = 0 ; i < 32 ; i++) {
/* Open 0.gcz, 1.gcz etc ... */
sprintf(filename, "%s/%d.gcz", in_dir, i);
f = fopen(filename, "rb");
if (f == NULL) break;
/* Read entire file */
fseek(f, 0, SEEK_END);
filesize = ftell(f);
fseek(f, 0, SEEK_SET);
fprintf(stderr, "%s: fread", filename);
lzss = malloc(filesize);
fread(lzss, filesize, 1, f);
fclose(f);
/* Decompress */
fprintf(stderr, "(OK) expand_lzss");
gc = expand_lzss(lzss, &out_sz);
free(lzss);
/* Unpack GC to 32-bit RGBA */
fprintf(stderr, "(OK) unpack_gc");
unpack_gc(&images[i], gc, out_sz);
free(gc);
fprintf(stderr, "(OK)\n");
}
/* Sanity check */
if (i == 0) {
fprintf(stderr, "No GCZ files found\n");
exit(EXIT_FAILURE);
}
/* Emit pile of TGAs */
fprintf(stderr, "split_images");
split_images(in_dir, out_dir, images, i);
fprintf(stderr, "(OK)\n\n");
return 0;
}
What is wrong with the code that could be causing this? The code is unaltered save for #define _CRT_SECURE_NO_WARNINGS being added to the code before the #include headers and having the program compiled as C.