C ++：程序因[memcpy]的核心转储而崩溃

Question

I'm working on Solaris 5.8, C++, using the Json parser.

The problem is: while parsing a file of size greater than 700 MB, the process crashes with core dump error. It roughly occurs at below code point -

int printbuf_memappend(struct printbuf *p, char *buf, int size)
{
    char *t;
    if(p->size - p->bpos <= size)
    {
        int new_size = json_max(p->size * 2, p->bpos + size + 8);
        if (!(t = realloc(p->buf, new_size)))
            return -1;
        p->size = new_size;
        p->buf = t;
    }
    memcpy(p->buf + p->bpos, buf, size); // CORE DUMP HERE
    p->bpos += size;
    p->buf[p->bpos]= '\0';
    return size;
}

Could you please help to identify the problem? The core dump file contain only the data being copied. Can increase of RAM be a solution ? Or do I need to limit the file size to 700MB ?

Answer 1

If crash happened in memcpy, you have two variants something wrong with input or output.

To test the second variant add memset after realloc:

    int new_size = json_max(p->size * 2, p->bpos + size + 8);
    if (!(t = realloc(p->buf, new_size)))
        return -1;
    p->size = new_size;
    p->buf = t;
    memset(p->buf + p->bpos, 0, size);

On Linux (depend on configuration) possible to allocate not existing virtual memory. The real allocation happens after the first usage. May the same happens on your Solaris? relloc return ok, but system really have no enought memory? memset should give answer to this question.