线程1：生成EXC_BAD_ACCESS（代码= 1，地址= 0x0）问题

Question

I'm using apple LLVM compiler for C++ development in Xcode. I initialise the char pickbuf variable and allocate the required memory I want to assign value 1 to second code of line there. But I'm getting a null pointer error: please help me.

2DCDP4.h

  class CDP : public Const2DCDP{

    struct PICK
        {
            short x;            // Transverse connector
            short y;            // Vertical direction consolidated
            unsigned char x0;   // Transverse reduction limit
            unsigned char y0;   // Longitudinal reduction limit
        } ;

    public:

        char*   pickbuf =new char[1];   // Overlapping buffer allocate some 
        PICK*   pickup =new PICK [1];       // Backtrace buffer

    }
void getProjection(void);
    };

2DCDP4.cpp

#include "2DCDP4.h"

void CDP::getProjection(void){
char    *before=pickbuf;
if( before[(j-1)*di + (i-1)] == 1) //**Thread 1 : EXC_BAD_ACCESS (Code = 1, address = 0x0)**
{
//code 
}
}

Answer 1

You haven't allocated any memory to pickbuf , but try to access the memory at pickbuf on the 2nd line. To fix this, allocate some memory to pickbuf before the 2nd line:

char pickbuf[n];

or

char* pickbuf = new char[n];

Where n is a size large enough for you needs.