0004273: Format.advance_left is not tail rec - MantisBT

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ID

Project

Category

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Date Submitted

Last Update

0004273

OCaml

OCaml general

public

2007-04-30 16:45

2008-09-08 14:35

Reporter

monate

Assigned To

weis

Priority

normal

Severity

crash

Reproducibility

always

Status

closed

Resolution

fixed

Platform

OS

OS Version

Product Version

3.09.3

Target Version

Fixed in Version

3.10.0

Summary

0004273: Format.advance_left is not tail rec

Description

Dear Caml'ers,

Calling Format.advance_left may raise Stack_overflow because it is not tail rec.
Here is a tentative fix :

let advance_left state =
let rec aux state =
    match peek_queue state.pp_queue with
     {elem_size = size; token = tok; length = len} ->
      let size = int_of_size size in
      if not
       (size < 0 &&
        (state.pp_right_total - state.pp_left_total < state.pp_space_left))
       then begin
        ignore(take_queue state.pp_queue);
        format_pp_token state (if size < 0 then pp_infinity else size) tok;
        state.pp_left_total <- len + state.pp_left_total;
        aux state
       end
  in
   try
   aux state
   with Empty_queue -> ();;

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Notes
(0004041) weis (developer) 2007-05-08 23:38	Have you indeed encountered such a stack overflow due to advance_left ? If so, could you please send me the example ? When I wrote advance_left, I was convinced that this could not happen :( That's why I'm really interested at reading a counterexample! Anyway, I already changed the code to get advance_left tailrec, since this could not hurt efficiency.

(0004042) monate (reporter) 2007-05-09 10:11	Yes I did encounter this stack overflow. Sadly, I cannot give you the example but here is a rough description. The code causing the stack overflow is a pretty printer for memory states of an analyzer of one very large C code. It uses a lot of nested %a and stack overflows after 12000 lines of output. Doubling the stack size fixes the problem. The patch prevents the stack overflow without changing the stack size. Thanks again.

(0004522) monate (reporter) 2008-06-16 11:05	The patch is still not present in 3.10.2 and the issue remains. The release process may have lost it.

(0004601) weis (developer) 2008-09-08 14:33	You were right: the fix was lost in the release process, or I forgot to report it in the relevant branch. This must be definitely fixed now :) Thanks for your feed back.

Issue History
Date Modified	Username	Field	Change
2007-04-30 16:45	monate	New Issue
2007-05-08 23:38	weis	Note Added: 0004041
2007-05-08 23:39	weis	Status	new => assigned
2007-05-08 23:39	weis	Assigned To	=> weis
2007-05-09 10:11	monate	Note Added: 0004042
2007-05-25 09:41	weis	Status	assigned => closed
2007-05-25 09:41	weis	Resolution	open => fixed
2007-05-25 09:41	weis	Fixed in Version	=> 3.10.0
2008-06-16 11:05	monate	Status	closed => feedback
2008-06-16 11:05	monate	Resolution	fixed => reopened
2008-06-16 11:05	monate	Note Added: 0004522
2008-09-08 14:33	weis	Note Added: 0004601
2008-09-08 14:35	weis	Status	feedback => closed
2008-09-08 14:35	weis	Resolution	reopened => fixed

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