Thread: SDL program returns 3, debugger gives Segmentation fault

Code:

Program received signal SIGSEGV, Segmentation fault.
0x000000000040161d in main (argc=1, args=0x7fffffffe278) at bar.cpp:194
194	    run( 0 , "Center!" , 290 , 180 , ( SW - text->w ) / 2 , 290 );
(gdb) print SW
$1 = 640
(gdb) print text
$2 = (SDL_Surface *) 0x0
(gdb)

You don't set text until the function is called.

Thanks a ton!

I re-wrote the code correctly this time, and now it (sort of) works.
It has some problem playing the sounds, some times at the first keystroke, other times at the second, but I'll try to figure this one out by myself.

Again, thank you very much for the help!

Code:

#include "SDL/SDL.h"
#include "SDL/SDL_image.h"
#include "SDL/SDL_ttf.h"
#include "SDL/SDL_mixer.h"
#include <string>

const int SW = 640;
const int SH = 480;
const int BPP = 32;

SDL_Surface * screen = NULL;
SDL_Surface * background = NULL;
SDL_Surface * faces = NULL;
SDL_Surface * text = NULL;

Mix_Chunk * up = NULL;
Mix_Chunk * down = NULL;
Mix_Chunk * left = NULL;
Mix_Chunk * right = NULL;

SDL_Rect clip[5];

SDL_Event event;

TTF_Font * font = NULL;
SDL_Color tcolor = { 255 , 255 , 255 };

bool init()
{
    if( SDL_Init( SDL_INIT_EVERYTHING ) == -1 )
    {
        return false;
    }

    screen = SDL_SetVideoMode( SW , SH , BPP , SDL_SWSURFACE );

    if( screen == NULL || TTF_Init() == -1 )
    {
        return false;
    }

    if( Mix_OpenAudio( 22050 , MIX_DEFAULT_FORMAT , 2 , 4096 ) == -1 )
    {
        return false;
    }

    SDL_WM_SetCaption( "Directions w/ sound!" , NULL );

    return true;
}

void clean()
{
    SDL_FreeSurface( background );
    SDL_FreeSurface( faces );
    SDL_FreeSurface( text );

    TTF_CloseFont( font );
    TTF_Quit();

    Mix_FreeChunk( up );
    Mix_FreeChunk( down );
    Mix_FreeChunk( left );
    Mix_FreeChunk( right );
    Mix_CloseAudio();

    SDL_Quit();
}

SDL_Surface * load( std::string file )
{
    SDL_Surface * loaded = NULL;
    SDL_Surface * optimized = NULL;

    loaded = IMG_Load( file.c_str() );

    if( loaded != NULL )
    {
        optimized = SDL_DisplayFormatAlpha( loaded );
        SDL_FreeSurface( loaded );
    }

    return optimized;
}

bool loadf()
{
    background = load( "bg.png" );
    faces = load( "d.png" );
    font = TTF_OpenFont( "Qarmic_sans_Abridged.ttf" , 24 );

    if( background == NULL )
    {
        return false;
    }

    if( faces == NULL )
    {
        return false;
    }

    if( font == NULL )
    {
        return false;
    }

    up = Mix_LoadWAV( "up.wav" );
    down = Mix_LoadWAV( "down.wav" );
    left = Mix_LoadWAV( "left.wav" );
    right = Mix_LoadWAV( "right.wav" );

    if( up == NULL || down == NULL || left == NULL || right == NULL )
    {
        return false;
    }

    return true;
}

void apply( int x , int y , SDL_Surface * get = NULL , SDL_Surface * give = NULL , SDL_Rect * clips = NULL )
{
    SDL_Rect off;

    off.x = x;
    off.y = y;

    SDL_BlitSurface( get , clips , give , &off );
}

void clipping()
{
    clip[0].x = 0;
    clip[0].y = 0;
    clip[0].w = 100;
    clip[0].h = 100;

    clip[1].x = 100;
    clip[1].y = 0;
    clip[1].w = 100;
    clip[1].h = 100;

    clip[2].x = 0;
    clip[2].y = 100;
    clip[2].w = 100;
    clip[2].h = 100;

    clip[3].x = 100;
    clip[3].y = 100;
    clip[3].w = 100;
    clip[3].h = 100;

    clip[4].x = 0;
    clip[4].y = 200;
    clip[4].w = 100;
    clip[4].h = 100;
}

void run( int n , std::string d , int fw , int fh )
{
    text = TTF_RenderText_Solid( font , d.c_str() , tcolor );

    if( text != NULL )
    {
        apply( 0 , 0 , background , screen );
        apply( fw , fh , faces , screen , &clip[n] );
        apply( fw , fh + 100 , text , screen );
    }

    SDL_Flip( screen );
}

int main( int argc , char * args[] )
{
    bool quit = false;

    if( init() == false )
    {
        return 2;
    }

    if( loadf() == false )
    {
        return 3;
    }

    if( clip != NULL )
    {
        clipping();
    }

    run( 0 , "Center!" , 290 , 180 );

    while( quit == false )
    {
        while( SDL_PollEvent( &event ) )
        {
            if( event.type == SDL_QUIT )
            {
                quit = true;
            }
        }

        Uint8 * keys = SDL_GetKeyState( NULL );

        if( keys[SDLK_UP] )
        {
            run( 1 , "Up!" , 290 , 10 );

            if( Mix_PlayChannel( -1 , up , 0 ) == -1 )
            {
                return 4;
            }
        }

        if( keys[SDLK_DOWN] )
        {
            run( 2 , "Down!" , 290 , 340 );

            if( Mix_PlayChannel( -1 , down , 0 ) == -1 )
            {
                return 5;
            }
        }

        if( keys[SDLK_LEFT] )
        {
            run( 3 , "Left!" , 10 , 180 );

            if( Mix_PlayChannel( -1 , left , 0 ) == -1 )
            {
                return 6;
            }
        }

        if( keys[SDLK_RIGHT] )
        {
            run( 4 , "Right!" , 530 , 180 );

            if( Mix_PlayChannel( -1 , right , 0 ) == -1 )
            {
                return 7;
            }
        }

        if( keys[SDLK_SPACE] )
        {
            run( 0 , "Center!" , 290 , 180 );
        }
    }

    clean();

    return 0;
}

SDL_GetError - SDL Documentation Wiki
Does this tell you anything, if you call it after the function has returned -1

Try moving all your Mix_PlayChannel's into one function that does NOTHING but take an input and play the given sound. And then replace it with just a line of text that prints what sound it thinks it should play. This will help eliminate things like you having to have time to hear the sound, playing "NULL" sounds, etc.

Compartmentalising your program like this is not only good programming practice but extremely helpful for debugging. I can't see anything at first sight but you call the functions multiple times inside an open loop that's likely to spin very fast so it's hard to tell what might go wrong.

Also, because of your loop, when it does work it's likely to loop so fast that it will play the sounds and fill every audio channel so long as you have the button down for more than a tiny fraction of a second. It will literally just keep playing the sound again and again while the button is down. Hell, from what I see you could be easily filling all audio channels with a single keypress and that's why Mix_PlayChannel fails. Either adjust your loop to "debounce" your input (i.e. only spot when the changes state, not look for if the key is currently pressed), or use SDL's proper keyboard events (you're already polling the event loop and could easily just check for the event being a key up/down event while you are there).

But, personally, I'd be pulling out all the PlayChannel's to find your problem and put them into a general purpose function that I would then debug the calling of (e.g. by temporarily replacing or supplementing the actual PlayChannel call inside it with a printf with some helpful information (e.g. the sound file played, the error from PlayChannel for that one, etc.).

I noticed your arguments to main are called argc and args, i've had issues with this before. Apparently SDL is picky about this, try renaming it to argv instead of args. I believe this mismatch results in a strange linker error so it's likely not the root of your issues, but worth a shot.

use your debug console to track keypresses and calls as suggested above