Question

I have a inline function defined as following:

inline string Change(char *pointer) {
    string str;
    char temp[32] = "";

    sprintf(temp,"%c:%c:%c:%c:%c:%c", //line 1
        temp[0],temp[1],temp[2],
        temp[3],temp[4],temp[5],
    );

    str = temp;
    return str;
}

when I use memory leak tool to check it, it indicates line 1(marked above) is memory leak.
What is the problem of the above code?

Answer 1

I created fully compilable example:

#include <string>
#include <iostream>
#include <cstdio>

std::string Change( char * ) {
    std::string str;
    char temp[32] = "";

    sprintf(temp,"%c:%c:%c:%c:%c:%c", //line 1
        temp[0],temp[1],temp[2],
        temp[3],temp[4],temp[5]
    );

    str = temp;
    return str;
}

int main()
{
    char a[]={"abaaaaa2"};
    std::cout<<Change(a)<<std::endl;
}

When running under valgrind, I get no leaks detected:

==16829== 
==16829== HEAP SUMMARY:
==16829==     in use at exit: 0 bytes in 0 blocks
==16829==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==16829== 
==16829== All heap blocks were freed -- no leaks are possible
==16829== 
==16829== For counts of detected and suppressed errors, rerun with: -v
==16829== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 15 from 8)