0003747: catch_break does not always catch break

Notes
(0000267) administrator (administrator) 2005-08-10 17:37	> Full_Name: Henri > Version: 3.08.2 > OS: linux > The following program never catches Ctrl+C in a terminal and loops forever. > let _ = > Sys.catch_break true; > try > while true do > () > done > with > Sys.Break -> prerr_endline "QUIT!" This is because signal handling has to be synchronized by the OCaml runtime: when a signal is caught, it sets a flag which is checked by the program from time to time... except in the rare case of a loop that doesn't allocate and doesn't call any function and is compiled with ocamlopt. The solution would be for the compiler to insert a test in every loop, but is it worth the trouble for something that almost never happens in a real program? > The following program does not catch break of course, but exits properly when > Ctrl+C is pressed in the same environment. > let _ = > try > while true do > () > done > with > Sys.Break -> prerr_endline "QUIT!" (* useless, kept anyway *) In this case, the signal is not caught, but the OS kills the process directly. -- Damien

(0000268) administrator (administrator) 2005-08-10 19:47	Damien, Thank you very much for the answer - maybe this should be added to the catch_break description. Btw, the third example was just meant to show that my term works correctly (which should never be taken for granted nowadays!). Regards, Henri On 8/10/05, Damien Doligez <caml-bugs@pauillac.inria.fr> wrote: > > Full_Name: Henri > > Version: 3.08.2 > > OS: linux > > > The following program never catches Ctrl+C in a terminal and loops forever. > > let _ = > > Sys.catch_break true; > > try > > while true do > > () > > done > > with > > Sys.Break -> prerr_endline "QUIT!" > > This is because signal handling has to be synchronized by the OCaml runtime: > when a signal is caught, it sets a flag which is checked by the program from > time to time... except in the rare case of a loop that doesn't allocate and > doesn't call any function and is compiled with ocamlopt. > > The solution would be for the compiler to insert a test in every loop, but > is it worth the trouble for something that almost never happens in a real > program? > > > > The following program does not catch break of course, but exits properly when > > Ctrl+C is pressed in the same environment. > > let _ = > > try > > while true do > > () > > done > > with > > Sys.Break -> prerr_endline "QUIT!" ( useless, kept anyway *) > > In this case, the signal is not caught, but the OS kills the process directly. > > -- Damien > >

(0000269) administrator (administrator) 2005-09-24 10:47	Issue is documented in ocamlopt chapter of ref. man. Feature wish: better polling for signals in ocamlopt-generated code. Unlikely to change any time soon. XL, 2005-09-24

Issue History
Date Modified	Username	Field	Change
2005-11-18 10:13	administrator	New Issue

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