Function try_realloc_chunk

system/lib/dlmalloc.c:4905–4982

Try to realloc; only in-place unless can_move true */

/* Try to realloc; only in-place unless can_move true */
static mchunkptr try_realloc_chunk(mstate m, mchunkptr p, size_t nb,
                                   int can_move) {
    mchunkptr newp = 0;
    size_t oldsize = chunksize(p);
    mchunkptr next = chunk_plus_offset(p, oldsize);
    if (RTCHECK(ok_address(m, p) && ok_inuse(p) &&
                ok_next(p, next) && ok_pinuse(next))) {
        if (is_mmapped(p)) {
            newp = mmap_resize(m, p, nb, can_move);
        }
        else if (oldsize >= nb) {             /* already big enough */
            size_t rsize = oldsize - nb;
            if (rsize >= MIN_CHUNK_SIZE) {      /* split off remainder */
                mchunkptr r = chunk_plus_offset(p, nb);
                set_inuse(m, p, nb);
                set_inuse(m, r, rsize);
                dispose_chunk(m, r, rsize);
            }
            newp = p;
        }
        else if (next == m->top) {  /* extend into top */
            if (oldsize + m->topsize > nb) {
                size_t newsize = oldsize + m->topsize;
                size_t newtopsize = newsize - nb;
                mchunkptr newtop = chunk_plus_offset(p, nb);
                set_inuse(m, p, nb);
                newtop->head = newtopsize |PINUSE_BIT;
                m->top = newtop;
                m->topsize = newtopsize;
                newp = p;
            }
        }
        else if (next == m->dv) { /* extend into dv */
            size_t dvs = m->dvsize;
            if (oldsize + dvs >= nb) {
                size_t dsize = oldsize + dvs - nb;
                if (dsize >= MIN_CHUNK_SIZE) {
                    mchunkptr r = chunk_plus_offset(p, nb);
                    mchunkptr n = chunk_plus_offset(r, dsize);
                    set_inuse(m, p, nb);
                    set_size_and_pinuse_of_free_chunk(r, dsize);
                    clear_pinuse(n);
                    m->dvsize = dsize;
                    m->dv = r;
                }
                else { /* exhaust dv */
                    size_t newsize = oldsize + dvs;
                    set_inuse(m, p, newsize);
                    m->dvsize = 0;
                    m->dv = 0;
                }
                newp = p;
            }
        }
        else if (!cinuse(next)) { /* extend into next free chunk */
            size_t nextsize = chunksize(next);
            if (oldsize + nextsize >= nb) {
                size_t rsize = oldsize + nextsize - nb;