为什么该程序以“未知信号”终止？

Question

以下代码用于在给定输入大小为N的情况下输出大小为1、2，...，N的组合。

#include <iostream>
#include <fstream>
#include <string>
#include <deque>
#include <cstring>
#include <iomanip>
#include <algorithm>
#include <exception>

template< typename V >
class Item
{
public:

  Item( const std::string& description,
        const V& value )
    : description_( description )
    , value_( value )
  {
  }

  std::string description() const { return description_; }

  V value() const { return value_; }

private:

  std::string description_;
  V value_;

friend std::ostream& operator<<( std::ostream& os, const Item& item )
{
  os << "{ \"" << item.description_ << "\", " << item.value_ << " }";
  return os;
}
};

template < typename T >
void addCombinationsN( const std::deque<T>& values,
                       std::deque<T>& interimResults,
                       size_t valuesStartIdx,
                       size_t n,
                       std::deque< std::deque<T> >& results )
{
  if ( valuesStartIdx >= values.size() ) { return; }
  if ( interimResults.size() >= n ) { return; }

  for ( int valuesIdx = valuesStartIdx;
        valuesIdx < values.size();
        ++valuesIdx )
  {
    interimResults.push_back( values[valuesIdx] );
    addCombinationsN( values, interimResults, valuesIdx+1, n, results );

    if ( interimResults.size() == n )
    {
      results.push_back( interimResults );
    }
    interimResults.pop_back();
  }
}

template < typename T >
std::deque< std::deque<T> > nChoose( const std::deque<T>& values )
{
  std::deque< std::deque<T> > retVal;
  std::deque<T> interimResults;

  std::cout << "adding all combinations from " << values.size() << " choices" << std::endl;

  for ( size_t n = 1; n <= values.size(); ++n )
  {
    std::cout << "# choices: " << n << std::endl;
    addCombinationsN < T > ( values, interimResults, 0, n, retVal );
  }
  std::cout << "done adding all choices" << std::endl;

  return retVal;
}

template< typename V >
class ItemDecCmp
{
public:
  bool operator()( std::deque< Item< V > >& a,
                   std::deque< Item< V > >& b ) const
  {
    return a.size() > b.size();
  }
};

template< typename V >
void populateChoices( std::deque< Item< V > >& items )
{
  for ( int i = 0; i < 28; ++i )
  {
    items.push_back( Item< V >( std::string( 1, '0' + i ), V(i) ) );
  }
}

int main( int argc, char* argv[] )
{
  std::deque< Item< double > > items;
  populateChoices<double>( items );

  std::deque< std::deque< Item< double > > > nChoices;
  nChoices = nChoose< Item< double > >( items );

  std::sort( nChoices.begin(), nChoices.end(), ItemDecCmp< double >() );
  std::cout << "done" << std::endl;

  for ( std::deque< std::deque< Item< double > > >::iterator i = nChoices.begin();
        i != nChoices.end();
        ++i )
  {
    for ( std::deque< Item< double > >::iterator j = i->begin();
          j != i->end();
          ++j )
    {
      std::cout << *j << " ";
    }
    std::cout << std::endl;
  }

  return 0;
}

代码会为元素少于30个的输入产生预期的输入结果（即调用populateChoices()的结果）。但是，如果输入容器中包含更多元素，则它会过早地终止而不会出现段错误。

输入3个元素的示例输出：

$ g++ -g main.cpp && ./a.exe
adding all combinations from 3 choices
# choices: 1
# choices: 2
# choices: 3
done adding all choices
done
{ "0", 0 } { "1", 1 } { "2", 2 }
{ "0", 0 } { "1", 1 }
{ "0", 0 } { "2", 2 }
{ "1", 1 } { "2", 2 }
{ "0", 0 }
{ "1", 1 }
{ "2", 2 }

输入28个元素的示例输出：

$ g++ -g main.cpp && ./a.exe
adding all combinations from 28 choices
# choices: 1
# choices: 2
# choices: 3
# choices: 4
# choices: 5
# choices: 6
# choices: 7
# choices: 8
# choices: 9
# choices: 10
# choices: 11

我尝试过的解决方法：

1）我怀疑由于递归算法的缘故，我可能会遇到堆栈溢出（无双关语）。但是，增加堆栈大小不会更改所描述的行为。

$ ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
file size               (blocks, -f) unlimited
open files                      (-n) 256
pipe size            (512 bytes, -p) 8
stack size              (kbytes, -s) 2032
cpu time               (seconds, -t) unlimited
max user processes              (-u) 256
virtual memory          (kbytes, -v) unlimited
$
$ ulimit -s 65536
$ ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
file size               (blocks, -f) unlimited
open files                      (-n) 256
pipe size            (512 bytes, -p) 8
stack size              (kbytes, -s) 65536
cpu time               (seconds, -t) unlimited
max user processes              (-u) 256
virtual memory          (kbytes, -v) unlimited
$ 

2）此代码最初使用std::vector而不是std::deque；我怀疑我的问题可能与按需重新分配std::vector在后​​台进行有关。我将容器切换到std::deque的前提是，push_back和pop_back不会导致重新分配（this Q&A，以及其他读物），但这也没有导致运行时行为发生任何变化。

3）我通过gdb运行了可执行文件，但无法知道其堆栈跟踪告诉了我什么：

(gdb) r
Starting program: /path/to/code/a.exe
[New Thread 11212.0x1884]
[New Thread 11212.0x18cc]
adding all combinations from 28 choices
# choices: 1
# choices: 2
# choices: 3
# choices: 4
# choices: 5
# choices: 6
[New Thread 11212.0x1eb4]
# choices: 7
# choices: 8
# choices: 9
# choices: 10
[New Thread 11212.0x2a5c]
[New Thread 11212.0xfa0]
# choices: 11
gdb: unknown target exception 0x20474343 at 0x7ffccb2754d8

Thread 1 "a" received signal ?, Unknown signal.
0x00007ffccb2754d8 in RaiseException () from /cygdrive/c/WINDOWS/System32/KERNELBASE.dll
(gdb) bt
#0  0x00007ffccb2754d8 in RaiseException () from /cygdrive/c/WINDOWS/System32/KERNELBASE.dll
#1  0x00000003e8ddcbf1 in cyggcc_s-seh-1!_Unwind_RaiseException () from /usr/bin/cyggcc_s-seh-1.dll
#2  0x00000003e8ddccc0 in cyggcc_s-seh-1!_Unwind_Resume_or_Rethrow () from /usr/bin/cyggcc_s-seh-1.dll
#3  0x00000003d0c57fcd in cygstdc++-6!.cxa_rethrow () from /usr/bin/cygstdc++-6.dll
#4  0x0000000100402ef7 in std::_Deque_base<Item<double>, std::allocator<Item<double> > >::_M_initialize_map (this=0x6fff5d6f7a0,
    __num_elements=11) at /usr/lib/gcc/x86_64-pc-cygwin/7.3.0/include/c++/bits/stl_deque.h:707
#5  0x000000010040307a in std::_Deque_base<Item<double>, std::allocator<Item<double> > >::_Deque_base (this=0x6fff5d6f7a0, __a=...,
    __num_elements=11) at /usr/lib/gcc/x86_64-pc-cygwin/7.3.0/include/c++/bits/stl_deque.h:500
#6  0x0000000100405209 in std::deque<Item<double>, std::allocator<Item<double> > >::deque (this=0x6fff5d6f7a0, __x=...)
    at /usr/lib/gcc/x86_64-pc-cygwin/7.3.0/include/c++/bits/stl_deque.h:949
#7  0x000000010040213f in __gnu_cxx::new_allocator<std::deque<Item<double>, std::allocator<Item<double> > > >::construct<std::deque<Item<double>, std::allocator<Item<double> > >, std::deque<Item<double>, std::allocator<Item<double> > > const&> (this=0xffffcb20,
    __p=0x6fff5d6f7a0, __args#0=...) at /usr/lib/gcc/x86_64-pc-cygwin/7.3.0/include/c++/ext/new_allocator.h:136
#8  0x0000000100404506 in std::allocator_traits<std::allocator<std::deque<Item<double>, std::allocator<Item<double> > > > >::construct<std::deque<Item<double>, std::allocator<Item<double> > >, std::deque<Item<double>, std::allocator<Item<double> > > const&> (__a=...,
    __p=0x6fff5d6f7a0, __args#0=...) at /usr/lib/gcc/x86_64-pc-cygwin/7.3.0/include/c++/bits/alloc_traits.h:475
#9  0x0000000100405b04 in std::deque<std::deque<Item<double>, std::allocator<Item<double> > >, std::allocator<std::deque<Item<double>, std::allocator<Item<double> > > > >::push_back (this=0xffffcb20, __x=...)
    at /usr/lib/gcc/x86_64-pc-cygwin/7.3.0/include/c++/bits/stl_deque.h:1547
#10 0x0000000100401b08 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=20, n=11, results=...)
    at main.cpp:58
#11 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=17, n=11, results=...)
    at main.cpp:54
#12 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=15, n=11, results=...)
    at main.cpp:54
#13 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=12, n=11, results=...)
    at main.cpp:54
#14 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=10, n=11, results=...)
    at main.cpp:54
#15 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=9, n=11, results=...)
    at main.cpp:54
#16 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=6, n=11, results=...)
    at main.cpp:54
#17 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=5, n=11, results=...)
    at main.cpp:54
#18 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=4, n=11, results=...)
    at main.cpp:54
#19 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=2, n=11, results=...)
    at main.cpp:54
#20 0x0000000100401ae1 in addCombinationsN<Item<double> > (values=..., interimResults=..., valuesStartIdx=0, n=11, results=...)
    at main.cpp:54
#21 0x0000000100401c1f in nChoose<Item<double> > (values=...) at main.cpp:75
#22 0x00000001004010d7 in main (argc=1, argv=0xffffcc20) at main.cpp:108

问题：

有人可以帮助您确定导致该程序崩溃的原因以及为什么它只是过早终止而不是可识别的信号，例如SEGV？

次要但相关的问题：为什么gdb标识正在创建的多个线程-这是一个单线程应用程序。我也不知道如何处理“未知目标异常”。

环境

在Windows 10 64位Intel PC上，开发环境为cygwin：

$ uname -a
CYGWIN_NT-10.0 My-PC 2.11.2(0.329/5/3) 2018-11-08 14:34 x86_64 Cygwin

PS-很抱歉问一个“帮助我调试”的问题，但是在这种情况下，因为我不知道该怎么gdb告诉我的内容，我真的很想如何识别具体错误的障碍。我在Meta上问这个问题是否最适合另一个Stack Exchange网站上的问题，在这里和Code Review之间意见分歧。

Answer 1

根据堆栈跟踪，异常会在调用内部引发

results.push_back( interimResults );

并且很可能是类型std::bad_alloc的异常，表明无法为std::deque的新元素分配内存，可能是因为不再有足够的可用内存。

由于interimResults总是很快又被pop_back删除，因此它的大小不会很大。但是results会变得很大，并且会消耗所有可用内存。

您根本无法存储那么多数据。您需要释放不需要的东西。