C++ valgrind 报错信息 segmentation fault

Question

我是 C++ 的新手，我正在尝试编写一个谜机模拟器。我知道我用我的指针做了一些奇怪的事情并且我已经通过 Valgrind 运行它，但我不确定错误消息的含义以及从哪里开始修复它？（泄漏摘要中的 suppressed 是什么意思？）

这是创建每个组件以及发生错误的部分代码。

Enigma::Enigma(int argc, char** argv){


errorCode = NO_ERROR;
plugboard = NULL;
*rotor = NULL;   //WHERE THE ERROR OCCURS
reflector = NULL;
rotorCount = 0;


//first check how many rotors there are
if (argc >= 5)
  rotorCount = argc - 4;
if (argc <= 4)       
  errorCode = INSUFFICIENT_NUMBER_OF_PARAMETERS;   

//pass files into each component and check if well-formed
if (errorCode == NO_ERROR){
  plugboard = new Plugboard(argv[1]);
  errorCode = plugboard -> errorCode;

if (errorCode == NO_ERROR){
  cout << "Plugboard configuration loaded successfully" << endl;
  reflector = new Reflector(argv[2]);
  errorCode = reflector -> errorCode;

  if (errorCode == NO_ERROR){
    cout << "Reflector configuration loaded successfully" << endl;
    rotor = new Rotor*[rotorCount];

    size_t i = 0;
    while (i < rotorCount && errorCode == NO_ERROR) {
      rotor[i] = new Rotor (argv[i+3]);
      i++;
      errorCode = rotor[i]-> errorCode;


      //destructor if rotor loading was unsuccessful 
      if (errorCode != NO_ERROR){
        for (int j=0; j<=i; j++)
          delete rotor[j];
        delete [] rotor;

这是 Valgrind 错误消息：

 reflectors/I.rf rotors/I.rot rotors/II.rot rotors/III.rot rotors/I.pos
 ==68943== Memcheck, a memory error detector
 ==68943== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
 ==68943== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
 ==68943== Command: ./enigma plugboards/I.pb reflectors/I.rf rotors/I.rot rotors/II.rot rotors/III.rot rotors/I.pos
 ==68943== 
 --68943-- run: /usr/bin/dsymutil "./enigma"
 ==68943== Use of uninitialised value of size 8
 ==68943==    at 0x100002598: Enigma::Enigma(int, char**) (enigma.cpp:17)
 ==68943==    by 0x100002F92: Enigma::Enigma(int, char**) (enigma.cpp:12)
 ==68943==    by 0x100000862: main (main.cpp:18)
 ==68943==  Uninitialised value was created by a stack allocation
 ==68943==    at 0x1000007D4: main (main.cpp:11)
 ==68943== 
 ==68943== Invalid write of size 8
 ==68943==    at 0x100002598: Enigma::Enigma(int, char**) (enigma.cpp:17)
 ==68943==    by 0x100002F92: Enigma::Enigma(int, char**) (enigma.cpp:12)
 ==68943==    by 0x100000862: main (main.cpp:18)
 ==68943==  Address 0x0 is not stack'd, malloc'd or (recently) free'd
 ==68943== 
 ==68943== 
 ==68943== Process terminating with default action of signal 11 (SIGSEGV)
 ==68943==  Access not within mapped region at address 0x0
 ==68943==    at 0x100002598: Enigma::Enigma(int, char**) (enigma.cpp:17)
 ==68943==    by 0x100002F92: Enigma::Enigma(int, char**) (enigma.cpp:12)
 ==68943==    by 0x100000862: main (main.cpp:18)
 ==68943==  If you believe this happened as a result of a stack
 ==68943==  overflow in your program's main thread (unlikely but
 ==68943==  possible), you can try to increase the size of the
 ==68943==  main thread stack using the --main-stacksize= flag.
 ==68943==  The main thread stack size used in this run was 10022912.
 ==68943== 
 ==68943== HEAP SUMMARY:
 ==68943==     in use at exit: 18,685 bytes in 166 blocks
 ==68943==   total heap usage: 187 allocs, 21 frees, 27,133 bytes allocated
 ==68943== 
 ==68943== LEAK SUMMARY:
 ==68943==    definitely lost: 0 bytes in 0 blocks
 ==68943==    indirectly lost: 0 bytes in 0 blocks
 ==68943==      possibly lost: 72 bytes in 3 blocks
 ==68943==    still reachable: 200 bytes in 6 blocks
 ==68943==         suppressed: 18,413 bytes in 157 blocks
 ==68943== Rerun with --leak-check=full to see details of leaked memory
 ==68943== 
 ==68943== For counts of detected and suppressed errors, rerun with: -v
 ==68943== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 1 from 1)
 Segmentation fault: 11

谢谢

Answer 1

也许你应该看看：How do pointer to pointers work in C?

基本上，我看到 rotor 是一个指向指针的指针或可能是一个指针数组（因为您将 *rotor 初始化为 NULL 并且后来还设置了 rotor[i] = new Rotor ).

确保您已正确初始化 rotor。它指向一个有效的对象吗？否则，您不能指望 *rotort = NULL /* or whatever value */; 工作。

Answer 2

基本上 suppressed 意味着内存泄漏到共享 libraries.And *rotor = NULL 代码之外，但它没有指向任何有效对象..

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