Consider bumping stack size in ruby_qsort
At the moment the maximum size of the stack is 32. The comment implies this should be enough for arrays with up to 2**32 elements, but it's possible to create larger arrays on some big systems.
I was not able to trigger a bug with: ([0, 1] * (2**32 + 10000)).sort! so it may actually never be a problem in practice, but it seems unsafe.
#1 [ruby-core:51817] Updated by Conrad.Irwin (Conrad Irwin) almost 5 years ago
- File 0001-Bump-stack-size-in-ruby_qsort-for-64-bit-CPUs.patch 0001-Bump-stack-size-in-ruby_qsort-for-64-bit-CPUs.patch added
Patch to bump size to 64
#2 [ruby-core:51818] Updated by duerst (Martin Dürst) almost 5 years ago
It's very well known that Quicksort may create stack overflows. But it's also very well known how to deal with them: Check which of the remaining divisions is longer, and user recursion for the sorter part, and tail recursion simulated with a loop for the longer one. For a (conceptual, written using Ruby as executable pseudocode) example, please see quick_sort_recurse at http://www.sw.it.aoyama.ac.jp/2012/DA/programs/6qsort.rb. I haven't checked the C code, but I would be extremely surprised if this and other optimizations would not have been used in Ruby's sort implementation.
#5 Updated by nobu (Nobuyoshi Nakada) almost 4 years ago
- Status changed from Open to Closed
- % Done changed from 0 to 100
This issue was solved with changeset r44195.
Conrad, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.
util.c: bump stack size in ruby_qsort()
- util.c (ruby_qsort): fix potential stack overflow on a large machine. based on the patch by Conrad Irwin at . [Bug #7772]