----- 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
>> r...@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.
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