0005626: Stack overflow in ocamlopt.opt: Comballoc.combine

Notes
(0007508) gasche (developer) 2012-06-03 19:40	As a simple workaround, you can chunk your code in smaller functions. Basically, ocamlopt works on functions one by one, and some compilation passes are not tail-recursive, but this is not an issue because they run at must on the inner code of a function, not on the whole program or even whole module. But "let () = ..."-style toplevel expressions are collected in a single "entry point" function that is handled like all other user-defined function. In your example, there are too many of them, and you reach your stack limit. By splitting these into smaller functions, you can avoid exhausting your stack. I tested for example with the following code adapted from yours, which packs your 50_000 phrases into 500 functions of 100 phrases each, and doesn't raise a Stack Overflow: echo "let h = Hashtbl.create 0 let add = Hashtbl.add h" > test.ml for f in `seq 1 500` do echo "let f () =" >> test.ml for i in `seq 1 100` do echo "let () = add \"$f$i\" \"bar\" in" >> test.ml done echo "()" >> test.ml echo >> test.ml echo "let () = f ()" >> test.ml echo >> test.ml done echo "let () = Gc.compact ()" >> test.ml Of course, this is only a workaround. A "better" solution would be to rewrite the involved functions to be tail-recursive, but that is a dubious enterprise: the different passes of the compiler are not tail-recursive, and what fails at the Comballoc step today may raise a Stack Overflow somewhere else tomorrow. Maintainers are not fond of chasing such changes through the compiler, when they degrade code readability (and performance) to fix problems that arise only in exceptional cases that can be relatively easily worked around.

(0007509) gasche (developer) 2012-06-03 19:43	(bug triaging hat on) I mark the bug "acknowledged" as the issue is real and easy to reproduce thanks to the reporter script, but my gut feeling is that this is too low-priority. If no developer stands up with an opinion on this, I'll probably move it into the "resolved > suspended" realm at some point in the future.

(0008139) doligez (manager) 2012-09-21 14:30	Setting to "confirmed" because I can reproduce the problem. Setting the priority to "low" because this impacts so few users. No idea whether we should spend time fixing this.

(0008935) smimram (reporter) 2013-02-28 11:12	A patch has been proposed in http://caml.inria.fr/mantis/view.php?id=5925 [^]

Issue History
Date Modified	Username	Field	Change
2012-05-29 17:30	Richard Jones	New Issue
2012-05-29 18:22	mehdi	Note Added: 0007471
2012-05-29 18:24	mehdi	Note Deleted: 0007471
2012-06-03 19:40	gasche	Note Added: 0007508
2012-06-03 19:43	gasche	Note Added: 0007509
2012-06-03 19:43	gasche	Status	new => acknowledged
2012-07-09 14:54	doligez	Target Version	=> 4.01.0+dev
2012-07-31 13:36	doligez	Target Version	4.01.0+dev => 4.00.1+dev
2012-09-21 14:30	doligez	Note Added: 0008139
2012-09-21 14:30	doligez	Priority	normal => low
2012-09-21 14:30	doligez	Status	acknowledged => confirmed
2012-09-21 14:30	doligez	Target Version	4.00.1+dev => 4.01.0+dev
2012-12-05 11:34	gasche	Relationship added	related to 0005844
2013-02-18 11:27	gasche	Relationship added	related to 0005925
2013-02-28 11:12	smimram	Note Added: 0008935