From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from concorde.inria.fr (concorde.inria.fr [192.93.2.39]) by pauillac.inria.fr (8.7.6/8.7.3) with ESMTP id TAA22653 for ; Mon, 21 Feb 2000 19:29:56 +0100 (MET) Received: from mail4.microsoft.com (mail4.microsoft.com [131.107.3.122]) by concorde.inria.fr (8.8.7/8.8.7) with SMTP id TAA07640 for ; Mon, 21 Feb 2000 19:29:57 +0100 (MET) Received: from 157.54.9.103 by mail4.microsoft.com (InterScan E-Mail VirusWall NT); Mon, 21 Feb 2000 10:29:16 -0800 (Pacific Standard Time) Received: by INET-IMC-04 with Internet Mail Service (5.5.2651.58) id ; Mon, 21 Feb 2000 10:29:15 -0800 Message-ID: <783D93998201D311B0CF00805FEAA07B7E9105@RED-MSG-42> From: Manuel Fahndrich To: "'David.Mentre@irisa.fr'" , caml-redistribution@pauillac.inria.fr Cc: colcombe@irisa.fr Subject: RE: Still strange GC problems with OCaml and C: OCaml 2.04 bug? Date: Mon, 21 Feb 2000 10:29:11 -0800 X-Mailer: Internet Mail Service (5.5.2651.58) I'm not suggesting that your problem is the same as the one described here http://pauillac.inria.fr/caml/caml-list/1415.html, but it's always a scenario to keep in mind. -Manuel -----Original Message----- From: David.Mentre@irisa.fr [mailto:David.Mentre@irisa.fr] Sent: Monday, February 21, 2000 9:18 AM To: caml-redistribution@pauillac.inria.fr Cc: colcombe@irisa.fr Subject: Still strange GC problems with OCaml and C: OCaml 2.04 bug? Hi all Camlists, I'm still fighting against my bug while trying to interface OCaml with CMU bdd library (in C). Following Xavier comments, I've protected my values (with CAMLparamXX and CAMLlocalXX macros). Actual code is available at: http://www.irisa.fr/paris/pages-perso/David-Mentre/bdd.ml http://www.irisa.fr/paris/pages-perso/David-Mentre/bdd_interface.c 1. I still obtain a segfault, however, the gdb backtrace has changed: (gdb) bt #0 0x80655b5 in mark_slice () #1 0x80659eb in major_collection_slice () #2 0x8065fd3 in minor_collection () #3 0x8063859 in interprete () #4 0x8065043 in caml_main () #5 0x805ab45 in main () #6 0x2ab457e2 in __libc_start_main () from /lib/libc.so.6 It is still a GC bug, however the problem no longer arises while our C interface allocates CAML memory. So I think the bug has moved (or this is another bug). 2. More interestingly, by compiling this code with OCaml 2.99 under sun4 architecture, this bug no longer occurs. I obtain in place a: Fatal error: uncaught exception Invalid_argument("Array.get") So, it would be possible that some Invalid_argument exceptions are not properly caught in OCaml 2.04. For CAML team, I was not able to produce a small/simple example that can trigger this bug. Only my gas-plant program seems to segfault. Sorry. 3. I've found an interesting message on Damien Doliguez site[1]: http://pauillac.inria.fr/~doligez/caml-guts/Fahndrich99.txt This message tells that you can have strange CAML GC related problems while deallocating C structures. However, I think my code is in case 2 of Manuel proposed fixes (i.e. box every C pointer inside an abstract CAML block). So, in my opinion, my bug is not related to this problem. But, as am I paranoid now :), I've set pointers to 1 after deallocating them. This not fixed the bug. Anyway, if somebody has an advice on how to track down this bug, I'll glady accept it. David -- once happy in the Caml-only world [1]http://pauillac.inria.fr/~doligez/caml-guts/ -- David.Mentre@irisa.fr -- http://www.irisa.fr/prive/dmentre/ Opinions expressed here are only mine.