C ++：传递从向量中获取的数组指针时的EXC_BAD_ACCESS

Question

Edit: I figured it out. When deflateReadOut() was instantiating the array was too large to be in the stack so it threw the EXC_BAD_ACCESS error when it was called. Useful link: link

This EXC_BAD_ACCESS error has me stumped. What my program does so far is make a 2D vector array containing four large unsigned char arrays, fills the one at position 0 with 100s and tries to pass the pointer pointing to this array with all 100s. However, when it gets to the function call the EXC_BAD_ACCESS error happens. I checked the integrity of the array by printing and it prints fine. Code below.

#include <stdint.h>
#include <map>
#include <stdio.h>
#include <iostream>
#include <time.h>
#include <string.h>
#include <assert.h>
#include <cstdlib>
#include <sstream>
#include <zlib.h>
#include "Hash.h"

#define CHUNK 16777216

using namespace std;

class WSUMap {
public:

    vector<vector <unsigned char> > chunk;
    int xComp[4];
    int yComp[4];
    vector<int> priority;
    Hash hashChunk;

    WSUMap() {
        chunk.reserve(4);
        chunk[0] = vector<unsigned char>(CHUNK);
        chunk[1] = vector<unsigned char>(CHUNK);
        chunk[2] = vector<unsigned char>(CHUNK);
        chunk[3] = vector<unsigned char>(CHUNK);
        priority.push_back(0);
        priority.push_back(1);
        priority.push_back(2);
        priority.push_back(3);
        xComp[0] = -1;
        xComp[1] = -1;
        xComp[2] = -1;
        xComp[3] = -1;
        yComp[0] = -1;
        yComp[1] = -1;
        yComp[2] = -1;
        yComp[3] = -1;
    }

    //Important part starts here:

    void generate() {
        for (int i = 0; i<CHUNK; i++) {
            chunk[0][i]=100;
        }
        for (int i = 0; i < 16; i++) {
            for (int j = 0; j < 16; j++) {
                cout << chunk[0][0] << endl;
                unsigned char* ch = &chunk[0][0];
                cout << ch[0] << endl;
                deflateReadOut(i, j, ch); //EXC_BAD_ACCESS Here
            }
        }
    }

    void deflateReadOut(int x, int y, unsigned char* chunk) {


        int ret, flush;
        unsigned have;
        z_stream strm;
        unsigned char out[CHUNK];

        /* allocate deflate state */
        strm.zalloc = Z_NULL;
        strm.zfree = Z_NULL;
        strm.opaque = Z_NULL;
        ret = deflateInit(&strm, 1);
        if (ret != Z_OK);
        //return ret;

        ostringstream oss;
        oss << "map/" << x << "x" << y;
        string str = oss.str();
        FILE* dest = fopen(str.c_str(), "w");

        /* run deflate() on input until output buffer not full, finish
           compression if all of source has been read in */
        do {
            strm.avail_out = CHUNK;
            strm.next_in = chunk;
            strm.next_out = out;

            ret = deflate(&strm, flush); /* no bad return value */
            assert(ret != Z_STREAM_ERROR); /* state not clobbered */

            have = CHUNK - strm.avail_out;
            if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                (void) deflateEnd(&strm);
                //return Z_ERRNO;
            }

        } while (strm.avail_out == 0);
        assert(strm.avail_in == 0); /* all input will be used */

        /* clean up and return */
        (void) deflateEnd(&strm);
    }

Thank you for any help you can give.

Answer 1

This:

chunk.reserve(4);

Should be:

chunk.resize(4);

Otherwise, you're just incrementing the capacity instead of the actual vector size.

You could also initialize the vector in the initialization list:

WSUMap() 
: chunk(4, vector<unsigned char>(CHUNK)) 
{

}

That's equivalent to incrementing the size and initializing the individual vectors.