std :: vector :: const_iterator未指向所需数据

Question

I have a std::vector<const char*> named log in a class Gui that I am trying to iterate through and use the values as arguments for a library function. The problem is that it seems to return incorrect/wrongly typed data.

void Gui::Message(const char *text, ...)
{
    char buffer[256];
    va_list args;
    va_start(args, text);
    vsnprintf(buffer, 256, text, args);
    va_end(args);
    log.emplace(log.begin(), buffer);
}

This formats the string properly and adds it to the vector. If I call puts(log.front()) after I emplace the buffer, it prints the correct output to the console. Also, if I emplace(text) instead of the buffer, it is displayed properly when Gui::render() is called, but it obviously isn't formatted.

void Gui::render()
{
    int y = 1;
    for(std::vector<const char*>::const_iterator iter = log.begin();
        iter != log.end(); iter++);
    {
        terminal_color("light grey");
        //takes x and y coordinates and a const char* and prints to the specified cell
        terminal_printf(1, 45 + y, "%s", (*iter));
        y++;
    }
}

Now if I call puts((*iter)) instead of the terminal print function, it still prints the incorrect data, so it doesn't appear to be a problem with the library function.

Refactoring the data structure for storing the messages is an option, but the strings need to be able to be properly formatted and passed to the library print function.

Answer 1

Your buffer is temporary storage valid only until the Message function returns. You are saving a pointer to where the buffer was, but its contents will be gone before the saved pointer is used.

If you want something that acts like a string, used std::string , don't misuse const char*

Answer 2

You're not pushing a const char* onto the buffer , you're putting a char that gets erased.

You use string and make your life easier.