Linux c++ 转string模板函数,写文件

#include <iostream>
#include <sstream>

using namespace std;
//转string模板函数
template <class T>
string toString(const T &v)
{
    ostringstream os;
    os << v;
    return os.str();
}

int main() {
    int a = ;
    float aa = 4.01;
    double dd = 33.566;
    string straa = toString(a);
    string straaa = toString(aa);
    string straab = toString(dd);

    cout << straa << endl;
    cout << straaa << endl;
    cout << straab << endl;

    return ;
}  

　　

int writeFile(string charFpName, string chVal) //写文件
{
	FILE *fp = fopen(charFpName.c_str(),"w+");
	if(NULL == fp){
		return 0;
	}
	fprintf(fp,"%s\n",chVal.c_str());
	fclose(fp);
	return 1;
}