standards/175453: Catching C++ std::bad_cast doesn't work in FreeBSD 9.1
Hongli Lai
hongli at phusion.nl
Sun Jan 20 17:00:01 UTC 2013
>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 at 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;
}
>Release-Note:
>Audit-Trail:
>Unformatted:
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