为什么在FreeBSD 9上无法捕获std :: bad_cast? [英] Why does catching std::bad_cast not work on FreeBSD 9?

问题描述

考虑以下代码(badcast.cpp):

Consider this code (badcast.cpp):

#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;
}

FreeBSD 9.1:

FreeBSD 9.1:

$ g++ badcast.cpp -o badcast -Wall && ./badcast
terminate called after throwing an instance of 'std::bad_cast'
  what():  std::bad_cast
Abort trap (core dumped)

$ g++ badcast.cpp -o badcast -frtti -fexceptions -Wall && ./badcast
terminate called after throwing an instance of 'std::bad_cast'
  what():  std::bad_cast
Abort trap (core dumped)

$ 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]

$ uname -a
FreeBSD freebsd9 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243825: Tue Dec  4 09:23:10 UTC 2012     [e-mail]:/usr/obj/usr/src/sys/GENERIC  amd64

Debian Linux 6:

Debian Linux 6:

$ g++ badcast.cpp -o badcast -Wall && ./badcast
bad cast

OS X 10.8:

OS X 10.8:

$ g++ badcast.cpp -o badcast -Wall && ./badcast
bad cast

为什么在FreeBSD上捕获bad_cast不起作用?

Why does catching bad_cast not work on FreeBSD?

推荐答案

作为一个疯狂的猜测，在FreeBSD中，您可能会使用LLVM的新 libc++ ，而不是旧的GNU libstdc++ . FreeBSD已经致力于切换到

As a wild guess, there’s a chance in FreeBSD you might be using LLVM’s new libc++, instead of the old GNU libstdc++. FreeBSD has been working towards switching over to the LLVM toolchain, away from GNU GPL licensed software.

苹果也在朝着这个方向发展，过去我遇到了使用libc++没有的(特别是使用Boost)使用libc++为Mac开发的问题.

Apple’s moving that way too, and in the past I’ve ran into issues developing for Mac using libc++ that libstdc++ didn’t have (especially with Boost).

您可以使用ldd确认要链接的库:

You can use ldd to confirm what libraries you’re linking against:

ldd ./badcast

如果它链接到libc++，则可能要使用 LLVM项目提交错误和测试用例.

If it is linking against libc++, you might want to file the bug and test case with the LLVM project.

这篇关于为什么在FreeBSD 9上无法捕获std :: bad_cast?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！