g++ 在正常编译时会产生段错误，但在 -g 时不会产生段错误

Question

我现在正在使用 Bruce Eckel 的“Thinking in C++”学习 C++，并且处于早期章节。我有 C 和 Java 背景。现在我遇到了以下问题：当我用

编译下面的源代码时

g++ A.cpp B.cpp bmain.cpp

，程序输出一个“1”（正确），然后是一个段错误。当我编译时

g++ -g A.cpp B.cpp bmain.cpp

，完全相同的程序产生 1 并且没有段错误！我不得不说我觉得这很惊人。有人可以指出我做错了什么吗？我的操作系统是“Linux 2.6.35-30-generic #54-Ubuntu x86_64”，我的 g++ 版本是“g++ (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5”。

编辑：仅仅因为这似乎是错误的一个重要来源，感谢@Evan Teran：B 结构中的 A 构造函数永远不会被调用！我放了一个 "cout

编辑：我现在在 main 末尾包含了“return 0”，但这无济于事。

啊哈：

#ifndef A_H
#define A_H

#include <string>

class A {
public:
        int i;
        std::string str;
        void print();
        A();
};

#endif

A.cpp：

#include "A.h"
#include <iostream>
#include <string>

using namespace std;

void A::print() {
        cout << str << " " << i << endl;
}

A::A() {
        str = "initstr";
    i = 0;
}

B.h：

#ifndef B_H
#define B_H

#include "A.h"

class B {
private:
        int counter;
public:
        A a;
        B();
        void increase();
        int read();
};

#endif

B.cpp：

#include "B.h"

using namespace std;

B::B() {
        counter = 0;
}

void B::increase() {
        ++counter;
}

int B::read() {
        return counter;
}

bmain.cpp:

#include <iostream>
#include "B.h"

using namespace std;

int main(int argc, char **argv) {
        B b;
        b.increase();
        cout << b.read() << endl;
        return 0;
}

编辑：我已经从包中安装了 g++。我的 Ubuntu 也很标准。

这是我打电话时得到的 gdb a.out 核心

warning: Can't read pathname for load map: Eingabe-/Ausgabefehler.
Reading symbols from /usr/lib/libstdc++.so.6...(no debugging symbols found)...done.
Loaded symbols for /usr/lib/libstdc++.so.6
Reading symbols from /lib/libm.so.6...Reading symbols from /usr/lib/debug/lib/libm-2.12.1.so...done.
done.
Loaded symbols for /lib/libm.so.6
Reading symbols from /lib/libgcc_s.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/libgcc_s.so.1
Reading symbols from /lib/libc.so.6...Reading symbols from /usr/lib/debug/lib/libc-2.12.1.so...done.
done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib64/ld-linux-x86-64.so.2...Reading symbols from /usr/lib/debug/lib/ld-2.12.1.so...done.
done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2
Core was generated by `./a.out'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007fba1049104b in std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() () from /usr/lib/libstdc++.so.6

编辑 2： 顺便说一句，据我所知，我的硬件没有故障，我对操作系统很好

编辑 3： Valgrind 报告如下：

==3428== Conditional jump or move depends on uninitialised value(s)
==3428==    at 0x4ECB022: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() (in /usr/lib/libstdc++.so.6.0.14)
==3428==    by 0x400D73: A::~A() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400D91: B::~B() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400CD7: main (in /home/xxx/C++/Exercises/ch04/a.out)
==3428== 
==3428== Use of uninitialised value of size 8
==3428==    at 0x4ECB04B: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() (in /usr/lib/libstdc++.so.6.0.14)
==3428==    by 0x400D73: A::~A() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400D91: B::~B() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400CD7: main (in /home/xxx/C++/Exercises/ch04/a.out)
==3428== 
==3428== Invalid read of size 4
==3428==    at 0x4ECB04B: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() (in /usr/lib/libstdc++.so.6.0.14)
==3428==    by 0x400D73: A::~A() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400D91: B::~B() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400CD7: main (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==  Address 0xfffffffffffffff8 is not stack'd, malloc'd or (recently) free'd
==3428== 
==3428== 
==3428== Process terminating with default action of signal 11 (SIGSEGV): dumping core
==3428==  Access not within mapped region at address 0xFFFFFFFFFFFFFFF8
==3428==    at 0x4ECB04B: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() (in /usr/lib/libstdc++.so.6.0.14)
==3428==    by 0x400D73: A::~A() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400D91: B::~B() (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==    by 0x400CD7: main (in /home/xxx/C++/Exercises/ch04/a.out)
==3428==  If you believe this happened as a result of a stack
==3428==  overflow in your program's main thread (unlikely but
==3428==  possible), you can try to increase the size of the
==3428==  main thread stack using the --main-stacksize= flag.
==3428==  The main thread stack size used in this run was 8388608.
==3428== 
==3428== HEAP SUMMARY:
==3428==     in use at exit: 0 bytes in 0 blocks
==3428==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==3428== 
==3428== All heap blocks were freed -- no leaks are possible    

Answer 1

您几乎肯定会在程序中的某处调用未定义的行为 (UB)。 UB 的重点是行为不仅是未定义的，而且可能会根据平台、编译器、标志等而改变。添加 -g 可能会以这样的方式扰乱事物以避免段错误，但这只是机会.

Answer 2

目前的情况似乎是 GCC/libstdc++ 打包/构建或使用的版本中的错误。试试 GCC 4.5 或 4.6，如果那里没有发生，告诉自己始终使用最新最好的（当然，直到它破坏某些东西）并且永远不要回头。

编译器似乎没有初始化B 中的A 成员，这将导致std::string 的析构函数无法读取必要的信息以正确自毁。但这只是推测和猜测。