Date: Sun, 20 Jan 2013 20:08:21 -0800 (PST) From: Pedro Giffuni <pfg@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com>, Hongli Lai <hongli@phusion.nl> Cc: "toolchain@freebsd.org" <toolchain@freebsd.org> Subject: Re: standards/175453: Catching C++ std::bad_cast doesn't work in FreeBSD 9.1 Message-ID: <1358741301.62974.YahooMailNeo@web162102.mail.bf1.yahoo.com> In-Reply-To: <20130121014745.GD2522@kib.kiev.ua> References: <201301201652.r0KGq0d1042817@red.freebsd.org> <20130121014745.GD2522@kib.kiev.ua>
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----- Messaggio originale ----- > Da: Konstantin Belousov > > On Sun, Jan 20, 2013 at 04:52:00PM +0000, Hongli Lai wrote: >> >> >Number: 175453 >> >Category: standards >> >Synopsis: Catching C++ std::bad_cast doesn't work in FreeBSD > 9.1 >> >Confidential: no >> >Severity: non-critical >> >Priority: low >> >Responsible: freebsd-standards >> >State: open >> >Quarter: >> >Keywords: >> >Date-Required: >> >Class: sw-bug >> >Submitter-Id: current-users >> >Arrival-Date: Sun Jan 20 17:00:00 UTC 2013 >> >Closed-Date: >> >Last-Modified: >> >Originator: Hongli Lai >> >Release: 9.1-RELEASE >> >Organization: >> Phusion >> >Environment: >> FreeBSD freebsd9 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243825: Tue Dec 4 > 09:23:10 UTC 2012 >> root@farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC amd64 >> >Description: >> C++ code is not able to catch std::bad_cast exceptions, even though it > should. If a dynamic_cast is within a try-catch block, then that block fails to > catch std::bad_cast, and the program crashes with an uncaught exception as a > result. >> >> I've attached a reproducible test case. You can also find it at > http://forums.freebsd.org/showthread.php?p=205804#post205804 and > http://stackoverflow.com/questions/14413703/why-does-catching-stdbad-cast-not-work-on-freebsd-9. > The code is compiled with the following GCC version: >> >> $ gcc -v >> Using built-in specs. >> Target: amd64-undermydesk-freebsd >> Configured with: FreeBSD/amd64 system compiler >> Thread model: posix >> gcc version 4.2.1 20070831 patched [FreeBSD] >> >> FreeBSD 9.1 seems to be the only platform on which this bug appears. The > code works as expected on Linux and OS X. According to a commenter, FreeBSD 9.0 > works as expected too. According to another commenter the code fails on FreeBSD > 9.1 with Clang too. >> >How-To-Repeat: >> See attached C++ program. >> >Fix: >> >> >> Patch attached with submission follows: >> >> #include <exception> >> #include <typeinfo> >> #include <stdio.h> >> >> class foo { >> public: >> virtual ~foo() {} >> }; >> >> class bar: public foo { >> public: >> int val; >> bar(): val(123) {} >> }; >> >> static void >> cast_test(const foo &f) { >> try { >> const bar &b = dynamic_cast<const bar &>(f); >> printf("%d\n", b.val); >> } catch (const std::bad_cast &) { >> printf("bad cast\n"); >> } >> } >> >> int main() { >> foo f; >> cast_test(f); >> return 0; >> } >> > Confirmed, and it seems that the culprit is libstdc++. At least replacing > the system libstdc++.so.6 with the library from the stock build of gcc > 4.7.2 (without touching libgcc_s.so.1) makes the catch operator working. > Confirmed, The problem is actually not in any of the code updates to libstdc++ but in the way libstdc++ is configured/build since 9.0. Reverting the changes in stable/9/gnu/lib/libstdc up to r229037 things work just fine. I suspect the culprit is r233749 and subsequent changes to build libstdc++ as a filter library for libsupc++. This also seems similar ot PR kern/171610. Pedro.home | help
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