Thread: va_list confusion

Hey there, hope you're having an awesome weekend!

So............... yeah, my brain hurts.

I have two functions that work with va_lists: one ("Say") that uses vsnprintf. It works in isolation. There other ("Write") calls Say and also the ncurses function "vw_printw" 9like a printf except that it also takes a va_list and works in the "ncurses" library). The ncurses part, obviously, also works in isolation. But when I try to put them both in the same function, "weird happens." For some reason, instead of putting the data (a const char * in my tests) into the string, it inserts the text "^P". I'm guessing the problem is the fact that I don't really know how va_lists work under the hood. There's probably some pointer moving somewhere, or something that got NULLed somehow... lol idk...

Anyway, here's the code:

Code:

void Say(bool rightNow, const char *format, ...) {
    /* Declare variables */
    va_list args;
    char buffer[256];
    
    /* Pass the variable arguments into our buffer */
    va_start(args, format);
    vsnprintf(buffer, 256, format, args);
    printw("Saying: \"%s\n\"", buffer);
    va_end (args);
    
    /* Stop speech if theuser wants this text spoken immediately */
    if (rightNow) espeak_Cancel();
    
    /* Tell eSpeak to speak our buffer */
    espeak_Synth((const char *)buffer, strlen(buffer) + 1, 0, POS_SENTENCE, 0, espeakCHARS_AUTO, NULL, NULL);
}

void Write(bool speakImmediately, const char * format, ...) {
    va_list list1, list2;
    
    va_start(list1, format);
    vw_printw(stdscr, format, list1);
    va_end(list1);
    
    // Tried a second va_list... no dice
    va_start(list2, format);
    Say(speakImmediately, (char *)format, list2);
    va_end(list2);
}

// Then the code that calls it, "Say" by itself seems to work.
Say(false, (char *)"What the %s?", "puck");
// Obviously, printw by itself works as well.
// But with this, I get "What the ^P?"
Write(false, "What the %s?", "puck");

At this point I'm considering abandoning my write function completely and just always calling speak and printw, which is kind of a setback (I'll have to add a lot more variables so I can pass them in to both functions etc.) but I can't find anything on the interwebz that would provide a logical explanation. Maybe passing a va_list to a function that uses a va_list is invalid somehow? Anyway I'm compiling this with GCC on 64-bit Linux Mint, using -Wall, and I'm not getting any warnings.

Thanks in advance.

Hahahahahaha wow, so simple, and yet so genius! Thank you so much! Man, why didn't I think of that?

So I get how this works - it's pretty obvious - but what I don't understand is why it was necessary. I'd be interested in any info you may have on the subject, but it's just out of curiosity now - I got some more hacking to do on this project now that I'm past this stupid bug!

I was under the impression that you could use _VA_ARGS__ in this case

But

It seem it can only be used in macros.