Question

I’ve got a character from the keyboard, by integer:

int c = getch();

an I want to append it to a string only if it isn’t a return:

void somefunction()
{
    std::string str = "you pressed: ";
    int c;
    while ( 1 )
    {
        c = getch();
        if ( c == 10 ) break;
        char* ch;
        sprintf(ch,"%c",c);
        str += std::string(ch);
    }
}

however, this creates a segmentation error when the scope of somefunction is left. I’m geussing that when the dtor for str is called the pointer to ch isn’t available any more.

How can I remedy this?

Answer 1

You are getting segmentation fault, because you are trying to sprintf string into unknown (not yet allocated) memory:

char* ch;
sprintf(ch,"%c",c);

possible fix of your code would be to replace char* ch; with char ch[2]; which would cause ch to become an statically allocated array with an automatic storage duration.

But note that since you are programming in C++ it would be wiser to use streams and methods of std::string rather than C-style (char*) strings and C-style functions like sprintf.