Re: Generally, are the programs written by C++ slower than written by C 10% ?

My test code:

#include<iostream>
#include<string>
#include<cstring>

int main() {
         clock_t tbeg;

         {
                 tbeg = clock();
                 for (int i = 0; i< 10000000; i++)
                         std::string("hello, world!");

                 std::cout<< "test 1 use "<< clock() - tbeg<<
std::endl;
         }

         {
                 tbeg = clock();
                 for (int i = 0; i< 10000000; i++) {
                         char* str = new char[20];
                         strcpy(str, "hello, world!");
                         delete [] str;
                 }

                 std::cout<< "test 2 use "<< clock() - tbeg<<
std::endl;
         }

         {
                 tbeg = clock();
                 for (int i = 0; i< 10000000; i++) {
                         char* str = (char*)malloc(20);
                         strcpy(str, "hello, world!");
                         free(str);
                 }

                 std::cout<< "test 3 use "<< clock() - tbeg<<
std::endl;
         }

         {
                 tbeg = clock();
                 for (int i = 0; i< 10000000; i++) {
                         char str[20];
                         strcpy(str, "hello, world!");
                 }

                 std::cout<< "test 4 use "<< clock() - tbeg<<
std::endl;
         }

         return 0;
}

output:
----------------------------
test 1 use 1260000
test 2 use 850000
test 3 use 610000
test 4 use 20000

So, could I think that if an object is constructed and destructed
frequently, I should make its member data are POD (not std::string or
some other expensive thing) ? Like this:

class temp_cache1 {
private:
         std::string s;
         std::vector<int> v;
};

class temp_cache2 {
private:
         char s[SIZE];
         int v[SIZE];
};

Here, is temp_cache2 better than temp_cache1?

I use valgrind trace the test program, found that the std::string
will allocation memory from heap even if the string is very short,
like std::string("abc"), it will allocation memory from heap.

So, either use temp_cache2 or use temp_cache1 and don't let it
destructed,
reuse its s and v. Am I right?