#include <assert.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* read_textfile(const char* filename)
{
    FILE* fp = fopen(filename, "r");
    if (!fp) {
        goto couldnt_read_file;
    }

    if (fseek(fp, 0, SEEK_END) != 0) {
        goto couldnt_read_file;
    }

    long file_size = ftell(fp);
    if (file_size < 0) {
        goto couldnt_read_file;
    }

    if (fseek(fp, 0, SEEK_SET) != 0) {
        goto couldnt_read_file;
    }

    char* buffer = malloc(file_size + 1);
    assert(buffer);

    if (fread(buffer, sizeof(char), file_size, fp) != (size_t)file_size) {
        goto couldnt_read_file;
    }

    buffer[file_size] = '\0';

couldnt_read_file:
    fprintf(stderr,
        "error: couldn't read file '%s': %s\n",
        filename,
        strerror(errno));
    return nullptr;
}

int main(int argc, char* argv[])
{
    if (argc < 2) {
        fprintf(stderr, "error: no filename\n");
        return EXIT_FAILURE;
    }
    char* filename = argv[1];
    char* text = read_textfile(filename);
    if (!text) {
        return EXIT_FAILURE;
    }
}