Question

function:

//http://www.cplusplus.com/reference/clibrary/ctime/strftime/
char* get_current_time()
{
    time_t rawtime;
    struct tm * timeinfo;
    char buffer [80];  //main.cpp:73: warning: address of local variable ‘buffer’ returned

    time ( &rawtime );
    timeinfo = localtime ( &rawtime );

    strftime (buffer,80,"%Y %m-%d %H-%M-%S",timeinfo);
    puts (buffer);
    return buffer;
}

which is invoked by:

char* filename = get_current_time();
filename = strcat(filename, ".txt");

and the puts outputs to the console:

2011 03-18 13-51-59

so… for the most part the function works…

but when I puts (filename); after the strcat, I get this:

p??_

Answer 1

Returning a LOCAL address is a bad bad bad idea.

In C++, std::string solves most of such issues. Prefer using it.

Also, forget about strcat, and use + or/and += with std::string.

Re-writing your code:

std::string get_current_time()
{
    time_t rawtime;
    struct tm * timeinfo;
    char buffer [80]; 

    time ( &rawtime );
    timeinfo = localtime ( &rawtime );

    strftime (buffer,80,"%Y %m-%d %H-%M-%S",timeinfo);
    puts (buffer);
    return buffer; //it converts into std::string automatically!
}

std::string filename = get_current_time();
filename += ".txt"; //concatenate. Compare it with strcat!

It looks better now.