+
+ if (brk == end && req < SIZE_MAX-brk
+ && !traverses_stack_p(brk, brk+req)
+ && __syscall(SYS_brk, brk+req)==brk+req) {
+ brk = end += req;
+ } else {
+ int new_area = 0;
+ req = n + PAGE_SIZE-1 & -PAGE_SIZE;
+ /* Only make a new area rather than individual mmap
+ * if wasted space would be over 1/8 of the map. */
+ if (req-n > req/8) {
+ /* Geometric area size growth up to 64 pages,
+ * bounding waste by 1/8 of the area. */
+ size_t min = PAGE_SIZE<<(mmap_step/2);
+ if (min-n > end-cur) {
+ if (req < min) {
+ req = min;
+ if (mmap_step < 12)
+ mmap_step++;
+ }
+ new_area = 1;
+ }
+ }
+ void *mem = __mmap(0, req, PROT_READ|PROT_WRITE,
+ MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+ if (mem == MAP_FAILED || !new_area) {
+ UNLOCK(lock);
+ return mem==MAP_FAILED ? 0 : mem;
+ }
+ cur = (uintptr_t)mem;
+ end = cur + req;