I am currently working on a toy python implementation. I was previously working on a Mac, but when I moved my project over to a Windows machine, I encountered an issue with reading file contents.

This is my file:

But for some reason, when I read it into memory, 12 is being appended to the end, as seen in the debug memory dump.

I am completely clueless as to what is causing this. Here is my source core for reading the file:

// OS-specific headers
#ifdef _WIN32

#include <io.h>
#define open _open
#define read _read

#else

#include <unistd.h>

#endif

namespace Parse
{
// Buffers the source file and creates a Lexer instance.
Lexer Lexer::from_src_file(const char *src_file_name)
{
    // Get a file descriptor for the source file.
    errno = 0;
    int fd = open(src_file_name, O_RDONLY);
    if (fd == -1)
        throw std::runtime_error{strerror(errno)};

    // Get the file information from the OS.
    struct stat file_stat {
    };
    errno = 0;
    if (fstat(fd, &file_stat) == -1)
        throw std::runtime_error{strerror(errno)};

    size_t file_size = file_stat.st_size;
    char *buffer = new char[file_size + 1];

    // Read the file into the buffer in chunks.
    constexpr int CHUNK_SIZE = 1024;

    size_t offset = 0;
    while (true) {
        size_t bytes_read = read(fd, buffer + offset, CHUNK_SIZE);
        if (!bytes_read)
            break;

        offset += bytes_read;
    }

    buffer[file_size] = EOF;

    // When we're done reading, close the file.
    close(fd);

    return Lexer{buffer, &buffer[file_size], src_file_name};
}

Any ideas as to what may be causing this?
Thanks in advance.