c++ - 为什么在这个函数中抛出这个 std::out_of_range ？

Question

下面是发生这个错误的函数:

std::string DataTranslation::getMeshName(std::string meshLink)
{
    File input(this->datafilename);
    std::cout << "the line count of " << this->datafilename << " = " << input.lineCount() << ".\n";
    std::cout << "code above is working properly if this prints.\n";
    return "_";
}

运行时:

the line count of ./res/data/resourcelist.data = 6.
code above is working properly if this prints.
terminate called after throwing an instance of 'std::out_of_range'
what(): vector::_M_range_check: __n (which is 0) >= this->size() (which is 0)

就是这样。之前的功能比较复杂，在调试的过程中我把它全部注释掉了，就剩下我上面写的了。异常似乎是由于 return "_"; 而引发的。

我是犯了一个基本错误还是真的很奇怪？

Answer 1

terminate called after throwing an instance of 'std::out_of_range'

terminate 被调用通常是由于异常“转义”了析构函数。

what(): vector::_M_range_check: __n (which is 0) >= this->size() (which is 0)

这通常在您对 std::vector 中的元素进行检查访问(想想 .at())时抛出。

因此，在 File 析构函数中寻找错误的检查 vector 访问。更好的是，要调试此类问题，请在调试器中运行您的程序，甚至可以在抛出的异常上添加断点(或在 std::terminate 上)；请注意，对于 gdb，这甚至不是必需的 - std::terminate 会导致 SIGABRT，它会自动进入调试器。

(gdb) r
Starting program: /home/matteo/scratch/a.out 
terminate called after throwing an instance of 'int'

Program received signal SIGABRT, Aborted.
0x00007ffff76c1418 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
54      ../sysdeps/unix/sysv/linux/raise.c: File o directory non esistente.
(gdb) bt
#0  0x00007ffff76c1418 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#1  0x00007ffff76c301a in __GI_abort () at abort.c:89
#2  0x00007ffff7ae484d in __gnu_cxx::__verbose_terminate_handler() ()
   from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3  0x00007ffff7ae26b6 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4  0x00007ffff7ae2701 in std::terminate() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007ffff7ae2919 in __cxa_throw () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6  0x000000000040077e in A::~A() ()
#7  0x0000000000400729 in foo() ()
#8  0x0000000000400749 in main ()
(gdb)