C/C++ 地址作为参数在函数内malloc后返回没有成功修改值

#include 
using namespace std;

void a(unsigned char* m_pBufForSaveImage){
    
    // m_pBufForSaveImage = (unsigned char*)malloc(100 * 100 * 3 + 2048);
    *m_pBufForSaveImage = 100;
    std::cout<<+*m_pBufForSaveImage<<" "<<+*(m_pBufForSaveImage+1)<

    unsigned char* srcImg;
    srcImg = (unsigned char*)malloc(100 * 100 * 3 + 2048);
    // unsigned int m_nBufSizeForSaveImage = 100 * 100 * 3 + 2048;

    a(srcImg);
    std::cout<<+*srcImg<<" "<<+*(srcImg+1)<