MATLAB: Matlab crash after running mex

MATLABMATLAB Builder EXmex

hello my matlab crash after runing mex file, please advise.
the matlab code:
function y = Shash(x,s,k,MM,bb,pass)
z = k/bb*2^bb;
y2 = uint32(Vhash2(uint8(z),s+pass,k,uint32(MM(x+1,:))));
the mex code:
#include "mex.h"
#include "string.h"
#include <math.h>
 
typedef unsigned int uint32_t;
 
#ifndef MWSIZE_MIN
typedef unsigned int mwSize;
#endif
 
uint32_t jenkins_one_at_a_time_hash(unsigned char *key, size_t key_len,uint32_t* Si)
{
    unsigned char temp[4];
    *temp= *key;
    unsigned char new_key[4];// = malloc(key_len);
    size_t i;
    for( i = 4; i > 0; i--)
    {
        new_key[i-1] = (unsigned char)((*temp)%2);//(unsigned char)((*(temp))%2);
        *temp >>= 1;
    }
    
    
    uint32_t hash = *Si;
    
    for (i = 0; i < 4; i++)
    {
        hash += new_key[i];
        hash += (hash << 10);
        hash ^= (hash >> 6);
    }
    hash += (hash << 3);
    hash ^= (hash >> 11);
    hash += (hash << 15);
    return hash;
}
 
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
    if (nlhs > 0)
    {
        mxArray  *HMatrix;
        int i;
        
        uint32_t *ph;
        uint32_t *phTemp;
        unsigned char *pd;
        uint32_t *mm;
        mwSize siz;
        
        pd = (unsigned char *)mxGetData(prhs[0]);
        
        mm= (uint32_t*)mxGetData(prhs[3]);
        siz = mxGetElementSize(prhs[3]);
        int z = *pd;
        uint32_t *res = 0;
        int j;
        unsigned char *array;
        array = (unsigned char *)mxMalloc(z*sizeof(unsigned char));;
        for (j = 0; j < z; j++)
        {
            array[j] = j + 1;
        }
        pd = array;
        siz = 1;
        
        HMatrix = mxCreateNumericMatrix(z, 1, mxUINT32_CLASS, mxREAL);
        
        ph = (uint32_t *)mxGetData(HMatrix);
        phTemp = (uint32_t *)mxMalloc(z*sizeof(uint32_t));;
        for(i = 0; i < z; ++i)
        {
            phTemp[i] = jenkins_one_at_a_time_hash(pd + i, (size_t)mxGetData(prhs[2]), (uint32_t*)mxGetData(prhs[1]));
            *res = *res + (mm[i]*phTemp[i]);
        }
        *ph = *res;
        plhs[0] = HMatrix;
        mxFree(array);
        mxFree(phTemp);
    }
}
thanks,
snir

Best Answer

        uint32_t *res = 0;
That is not a pointer to a value that is 0: that is setting the res pointer to NULL because C defines assigning 0 to a pointer to be equivalent to assigning NULL to it. (C++ has moved away from that.) You are therefore writing into low memory, with undefined results.
If you want a pointer to a 0 then
        uint32_t res_data = 0;
        uint32_t *res = &res_data;
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