wprintf 사용시에만 멤버함수가 호출되는 이유는 뭔가요?

#include <cstdio>
#include "s_cstdlib.h"
#include "DynamicArr.h"
#include <clocale>
#include <climits>
#include <cstring>
#include <cstdlib>
#include "s_ifstream.h"
#include <cwchar>
#include <fstream>
 
int main() {
	//wprintf(L"e\n");//  1) 주석
	setlocale(LC_ALL,"ko_KR.UTF-8");
	DynamicArr<char> arr1(strlen("abcdefg")+1);
	arr1="abcdefg";//trouble
	arr1.output();printf("\n");
	printf("%s\n",&arr1[0]);
 
	DynamicArr<wchar_t> arr2(wcslen(L"computer")+1);
	arr2=L"computer";// 2) 주석
	arr2[arr2.count()-1]=0;
	wprintf(L"%u\n",arr2.count());
	arr2.output();
	wprintf(L"\neffe  %ls\n",&arr2[0]);
 
	wprintf(L"%u\n",arr2.length);
        return 0
}