无法理解这个 SEGFAULT

Question

我正在编写一个 c/c++ SDL 合成器，它在 linux、windows 上运行，并处理 psp，我在多个部分混合 c/c++编码。我使用 new/malloc，我认为我没有混淆它们，但如果我混淆了，请告诉我在哪里以及为什么。

我的主程序现在接近 20 000 行并且运行良好。但是我总是在开始修改它时陷入错误，我无法理解和发现我真正的错误。

当我开始修改我的代码的某些部分时，我陷入了 SIGSEV，我花了好几个小时才让它工作，但我不明白为什么我会陷入这个境地。经过一些修改后它再次工作，我不知道为什么我有一个 SIGSEV 以及为什么它现在已修复以及我如何修改它以使其工作并防止将来出错。所以我请你解释一下我真正的错误是什么。

这是一个 gdb 日志，其中包含真正简化的版本和我遇到的崩溃类型：

    yoyz@yoyz-laptop:~/build/audio/picoloop/tmp/ gdb ./WaveTable 
    GNU gdb (GDB) 7.4.1-debian
    Copyright (C) 2012 Free Software Foundation, Inc.
    License GPLv3+: GNU GPL version 3 or later         <http://gnu.org/licenses/gpl.html>
    This is free software: you are free to change and redistribute it.
    There is NO WARRANTY, to the extent permitted by law.  Type "show         copying"
    and "show warranty" for details.
    This GDB was configured as "x86_64-linux-gnu".
    For bug reporting instructions, please see:
    <http://www.gnu.org/software/gdb/bugs/>...
    Reading symbols from         /home/yoyz/build/audio/picoloop/tmp/WaveTable...done.
    (gdb) r
    Starting program: /home/yoyz/build/audio/picoloop/tmp/WaveTable 
    warning: the debug information found in "/lib64/ld-2.13.so" does not         match "/lib64/ld-linux-x86-64.so.2" (CRC mismatch).

    Generator::init() Allocating memory
    Generator::one() 0x00604010
    Generator::sine() 0x00604010
    Generator::saw() 0x00604010
    Generator::pulse() 0x00604010

    Program received signal SIGSEGV, Segmentation fault.
    _int_malloc (av=0x7ffff7639e40, bytes=32768) at malloc.c:4738
    4738    malloc.c: No such file or directory.
    (gdb)

这是代码的简化版本：

    #include "MyMaster.h"
    #include "Generator.h"
    #include "WaveTable.h"
    #include "WaveTableManager.h"


    int main(int argc,char **argv)
    {
      Generator G;
      WaveTableManager & WTM = WaveTableManager::getInstance();
      WaveTable* WT;

      G.init();


      WT = new WaveTable();
      WT->setSize(WAVETABLE_SIZE);
      G.one();
      memcpy(WT->getBuffer(),G.getBuffer(),WAVETABLE_SIZE*DEFAULTBITRATE/8);
      WTM.insert(WT,PICO_WAVETABLE_ONE);


      WT = new WaveTable();
      WT->setSize(WAVETABLE_SIZE);
      G.sine();
      memcpy(WT->getBuffer(),G.getBuffer(),WAVETABLE_SIZE*DEFAULTBITRATE/8);
      WTM.insert(WT,PICO_WAVETABLE_SINE);



      WT = new WaveTable();
      WT->setSize(WAVETABLE_SIZE);
      G.saw();
      memcpy(WT->getBuffer(),G.getBuffer(),WAVETABLE_SIZE*DEFAULTBITRATE/8);
      WTM.insert(WT,PICO_WAVETABLE_SAW);


      WT = new WaveTable();
      WT->setSize(WAVETABLE_SIZE);
      G.pulse();
      memcpy(WT->getBuffer(),G.getBuffer(),WAVETABLE_SIZE*DEFAULTBITRATE/8);
      WTM.insert(WT,PICO_WAVETABLE_PULSE);


      WT = new WaveTable();
      WT->setSize(WAVETABLE_SIZE);
      G.triangle();
      memcpy(WT->getBuffer(),G.getBuffer(),WAVETABLE_SIZE*DEFAULTBITRATE/8);
      WTM.insert(WT,PICO_WAVETABLE_TRGL);


      WT = new WaveTable();
      WT->setSize(WAVETABLE_SIZE);
      G.noise();
      memcpy(WT->getBuffer(),G.getBuffer(),WAVETABLE_SIZE*DEFAULTBITRATE/8);
      WTM.insert(WT,PICO_WAVETABLE_NOISE);


      printf("wavetablemanager.getSize : %d\n",WTM.getSize());

    }

MyMaster.h

    #ifndef __MASTER____
    #define __MASTER____
    #include <SDL/SDL.h>
    #define WAVETABLE_SIZE  1024*16
    #define DEFAULTBITRATE   16

    enum 
      {
        PICO_WAVETABLE_SINE,
        PICO_WAVETABLE_SAW,
        PICO_WAVETABLE_PULSE,
        PICO_WAVETABLE_TRGL,
        PICO_WAVETABLE_NOISE,
        PICO_WAVETABLE_ONE,
        PICO_WAVETABLE_SIZE
      };

    #endif

Generator.h

    using namespace std;

    #include <SDL/SDL_types.h>
    #include <math.h>
    #include "MyMaster.h"

    #ifndef __GENERATOR__
    #define __GENERATOR__

    class Generator 
    {
    public:
      Generator();
      ~Generator();
      void init();
      void sine();
      void saw();
      void pulse();
      void triangle();
      void noise();
      void one();
      Sint16 * getBuffer();

     private:
      Sint16 * table;
      int      table_size;
      int      index;
      int      d;

    };
    #endif

Generator.cpp

    #include "Generator.h"

    Generator::Generator()
    {
      table_size=WAVETABLE_SIZE;
    }

    Generator::~Generator()
    {
    }

    void Generator::init()
    {
      if (table_size>0)
        {
          printf("Generator::init() Allocating memory\n");
          table=(Sint16*)malloc(sizeof(Sint16)*table_size);
          if (table==0)
            {
              printf("Error allocating memory\n");
              //return 0;
            } 
        }   
    }   

    void Generator::sine()
    {
      int i;
      float f;
      Sint16 s;
      Sint16 bitdepth=16-1;
      printf("Generator::sine() 0x%08.8X\n",table);
      for (i=0;i<table_size;i++)
        {
          s=sin((2*3.14159*i*1)/table_size)*(1<<bitdepth-2);
          table[i]=s;
          //printf("table[%d]=%d\n",i,s);
        }
    }

    void Generator::saw()
    {
      int i;
      float f;
      Sint16 s;
      Sint16 bitdepth=16;
      Sint16 dec;

      printf("Generator::saw() 0x%08.8X\n",table);

      s=(1<<(bitdepth-2));
      dec=(1<<(bitdepth-2))/(table_size/2);

      for (i=0;i<table_size;i++)
        {
          table[i]=s;
          s=s-dec;
        }
    }

    void Generator::pulse()
    {
      int i;
      float f;
      Sint16 s;
      Sint16 bitdepth=16;
      Sint16 dec=(1<<(bitdepth-2))/(table_size/2);

      printf("Generator::pulse() 0x%08.8X\n",table);

      for (i=0;i<table_size/2;i++)
        {
          table[i]=((1<<(bitdepth-2))/2);
        }
      for (i=table_size/2;i<table_size;i++)
        {
          table[i]=((1<<(bitdepth-2))*-1)/2;
        }
    }

    void Generator::triangle()
    {
      int i;
      float f;
      Sint16 s=0;
      Sint16 bitdepth=16;
      Sint16 dec=(1<<(bitdepth-2))/(table_size/4);

      printf("Generator::triangle() 0x%08.8X\n",table);

      //table=(Sint16*)malloc(sizeof(Sint16)*table_size);
      for (i=0;i<(table_size*1)/4;i++)
        {
          table[i]=s;
          s=s+dec;
        }
      for (i=(table_size*1)/4;i<(table_size*3)/4;i++)
        {
          table[i]=s;
          s=s-dec;
        }
      for (i=(table_size*3)/4;i<table_size;i++)  
        {
          table[i]=s;
          s=s+dec;
        }
    }


    void Generator::noise()
    {
      int i;
      float f;
      Sint16 s;
      Sint16 bitdepth=16;

      printf("Generator::noise() 0x%08.8X\n",table);

      srand(1<<(bitdepth-2));
      for (i=0;i<table_size;i++)
        {
          if (rand()%2==0)
            table[i]=rand()%8192;
          else
            table[i]=(rand()%8192)*-1;
        }
    }

    void Generator::one()
    {
      int i;
      float f;
      Sint16 s;
      Sint16 bitdepth=16;

      printf("Generator::one() 0x%08.8X\n",table);

      for (i=0;i<table_size;i++)
        {
          table[i]=1<<bitdepth-1;
        }
    }



    Sint16 * Generator::getBuffer()
    {
      return table;
    }

WaveTable.h

    #include "MyMaster.h"
    #include <SDL/SDL_types.h>
    #ifndef __WAVETABLE__
    #define __WAVETABLE__

    class WaveTable
    {
     public:
      WaveTable();
      ~WaveTable();

       int      setSize(int bufferSize); 
       int      allocMemory();
       int      freeMemory(); 


      Sint16 * getBuffer();
      char   * getName();
      Sint32   getSize();



     private:
      Sint32   size;
      Sint16 * buffer;
      char   * name;

    };

    #endif

WaveTable.cpp

    #include "WaveTable.h"
    using namespace std;

    WaveTable::WaveTable()
    {
      size=0;
      buffer=0;
      name=0;
    }

    WaveTable::~WaveTable()
    {
    }


    int WaveTable::allocMemory()
    {
      if (size>0)
        {
          buffer=(Sint16*)malloc(sizeof(Sint16)*size);
          if (buffer==0)
            {
              printf("Error allocating memory\n");
              return 0;
            }
        }
      return size;
    }


    int WaveTable::freeMemory()
    {
      if (buffer!=0)
        {
          free(buffer);
          buffer=0;
        }
    }

    int WaveTable::setSize(int bufferSize)
    {
      if (bufferSize>=0)
        size=bufferSize;

      if (buffer!=0)
        this->freeMemory();
      return this->allocMemory();
    }

    Sint16 * WaveTable::getBuffer()
    {
      return buffer;
    }

WaveTableManager.h

    using namespace std;

    #include <vector>
    #include "WaveTable.h"

    #ifndef __WAVETABLEMANAGER__
    #define __WAVETABLEMANAGER__

    class WaveTableManager 
    {
    private:

      WaveTableManager();
      ~WaveTableManager();

      vector<WaveTable*> wtvector;  

      int    size;


    public:
      static WaveTableManager& getInstance();

      int         getSize();
      void        insert(WaveTable * WT,int position);
      WaveTable * get(int position);


    };
    #endif

WaveTableManager.cpp

    #include "WaveTableManager.h"

    WaveTableManager::WaveTableManager() : wtvector()
    {
      size=0;
    }


    WaveTableManager::~WaveTableManager()
    {

    }



    WaveTableManager& WaveTableManager::getInstance()
    {
      static WaveTableManager instance;
      return instance;
    }


    int WaveTableManager::getSize()
    {
      return wtvector.size();
    }

    void WaveTableManager::insert(WaveTable * WT,int position)
    {
      if (wtvector.size()<=position)
        wtvector.resize(position);
      wtvector[position]=WT;
    }


    WaveTable * WaveTableManager::get(int position)
    {
      return wtvector[position];
    }

Makefile.WaveTable

    CC=g++

    CFLAGS=-O0 -DLINUX -D__RTAUDIO__ -DLINUX_DESKTOP -I. -LSDL/lib -g -fpermissive
    SOURCES=WaveTableTest.cpp WaveTable.cpp WaveTableManager.cpp Generator.cpp
    OBJECTS=$(SOURCES:.cpp=.o)
    EXECUTABLE=WaveTable

    all: $(SOURCES) $(EXECUTABLE)

    $(EXECUTABLE): $(OBJECTS)
            $(CC) $(LDFLAGS) $(OBJECTS) -o $@

    .cpp.o:
            $(CC) -c $(CFLAGS) $< -o $@

    clean:
            -rm -f $(OBJECTS) $(EXECUTABLE)

Answer 1

这是一期：

void WaveTableManager::insert(WaveTable * WT,int position)
{
  if (wtvector.size()<=position)
    wtvector.resize(position);
  wtvector[position]=WT;  // < -- Out of bounds access
}

调用resize()时，上限为vector::size()-1。由于 position 是向量的新大小，您可能想要的是：

  wtvector[position - 1] = WT;

无法理解这个 SEGFAULT

can not understand this SEGFAULT

c++

linux

g++

segmentation-fault