Discussion:
cannot convert 'SDL_DisplayMode' to 'SDL_DisplayMode*
(too old to reply)
speartip
2017-02-08 01:20:30 UTC
Permalink
Hi,

I am struggling with some pretty straight forward c/c++ & SDL code. But I am not feeling the straightforwardness of it though. I don't know if its a c++ issue or SDL. I try to call SDL fx code from an external .cpp/.h. I am trying to make these reusable and to release main from clutter. Everything runs smoothly until the second block:


Code:

int horizontal = 0;
int vertical = 0;
SDL_DisplayMode dm;
cout<<"Gobot call:";
gobot(horizontal, vertical,&dm);





Code:

#ifndef GOBOT_CPP_
#define GOBOT_CPP_

#include "SDL.h"
#include "gobot.h"


int gobot( int &horizontal, int &vertical, &dm )
{
//SDL_GetDesktopDisplayMode(0, &dm);
horizontal = dm->w;
vertical = dm->h;
return 0;
}
//cout<<"Resolution: x = "<<Width<<" y = "<<Height<<endl;
#endif /* GOBOT_CPP_ */





Code:

#ifndef GOBOT_H_
#define GOBOT_H_
#include"SDL.h"

int SDL_GetDesktopDisplayMode(int displayIndex, SDL_DisplayMode * dm);
int gobot(int horizontal, int vertical, SDL_DisplayMode * dm);

#endif /* GOBOT_H_ */




error:
In function 'int SDL_main(int, char**)':
..\src\SpearTip.cpp:50:35: error: cannot convert 'SDL_DisplayMode' to 'SDL_DisplayMode*' for argument '3' to 'int gobot(int, int, SDL_DisplayMode*)'
gobot(horizontal, vertical, dm);

Thanks
Brian Puthuff
2017-02-08 02:11:21 UTC
Permalink
Your .H function declaration (prototype) for gobot and your .CPP function
need to have the same arguments and return types.
If your goal is to pass horizontal and vertical and dm into the function,
and then store the display mode's width and height data into horizontal and
vertical respectively, then you need to have the function take in pointers
to horizontal and vertical. Then in your function definition, deference
your pointers and store the values obtained by dm. Hopefully that makes
sense.


Code:

int horizontal = 0;
int vertical = 0;
SDL_DisplayMode dm;
cout<<"Gobot call:";
gobot(&horizontal, &vertical, &dm);


In your .CPP Definition:

int gobot( int* horizontal, int* vertical, SDL_DisplayMode* dm )
{
//SDL_GetDesktopDisplayMode(0, &dm);
*horizontal = dm->w;
*vertical = dm->h;
return 0;
}

In your .H Declaration
int gobot( int* horizontal, int* vertical, SDL_DisplayMode* dm );
Post by speartip
Hi,
I am struggling with some pretty straight forward c/c++ & SDL code. But I
am not feeling the straightforwardness of it though. I don't know if its a
c++ issue or SDL. I try to call SDL fx code from an external .cpp/.h. I am
trying to make these reusable and to release main from clutter. Everything
int horizontal = 0;
int vertical = 0;
SDL_DisplayMode dm;
cout<<"Gobot call:";
gobot(horizontal, vertical,&dm);
#ifndef GOBOT_CPP_
#define GOBOT_CPP_
#include "SDL.h"
#include "gobot.h"
int gobot( int &horizontal, int &vertical, &dm )
{
//SDL_GetDesktopDisplayMode(0, &dm);
horizontal = dm->w;
vertical = dm->h;
return 0;
}
//cout<<"Resolution: x = "<
#ifndef GOBOT_H_
#define GOBOT_H_
#include"SDL.h"
int SDL_GetDesktopDisplayMode(int displayIndex, SDL_DisplayMode * dm);
int gobot(int horizontal, int vertical, SDL_DisplayMode * dm);
#endif /* GOBOT_H_ */
..\src\SpearTip.cpp:50:35: error: cannot convert 'SDL_DisplayMode' to
'SDL_DisplayMode*' for argument '3' to 'int gobot(int, int,
SDL_DisplayMode*)'
gobot(horizontal, vertical, dm);
Thanks
_______________________________________________
SDL mailing list
http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org
Clangray
2017-02-08 23:56:42 UTC
Permalink
I made the exact changes; still getting errors:



.\src\gobot.cpp:15:45: error: 'dm' has not been declared

int gobot( int * horizontal, int* vertical, dm )

^

..\src\gobot.cpp: In function 'int gobot(int*, int*, int)':

..\src\gobot.cpp:18:18: error: 'dm' was not declared in this scope

* horizontal = dm->w;





--

Gray Family
Post by Brian Puthuff
Your .H function declaration (prototype) for gobot and your .CPP
function need to have the same arguments and return types.
If your goal is to pass horizontal and vertical and dm into the
function, and then store the display mode's width and height data into
horizontal and vertical respectively, then you need to have the
function take in pointers to horizontal and vertical. Then in your
function definition, deference your pointers and store the values
obtained by dm. Hopefully that makes sense.
int horizontal = 0;
int vertical = 0;
SDL_DisplayMode dm;
cout<<"Gobot call:";
gobot(&horizontal, &vertical, &dm);
int gobot( int* horizontal, int* vertical, SDL_DisplayMode* dm )
{
//SDL_GetDesktopDisplayMode(0, &dm);
*horizontal = dm->w;
*vertical = dm->h;
return 0;
}
In your .H Declaration
int gobot( int* horizontal, int* vertical, SDL_DisplayMode* dm );
On Tue, Feb 7, 2017 at 5:20 PM, speartip
Post by speartip
__
Hi,
I am struggling with some pretty straight forward c/c++ & SDL code.
But I am not feeling the straightforwardness of it though. I don't
know if its a c++ issue or SDL. I try to call SDL fx code from an
external .cpp/.h. I am trying to make these reusable and to release
int horizontal = 0;
int vertical = 0;
SDL_DisplayMode dm;
cout<<"Gobot call:";
gobot(horizontal, vertical,&dm);
#ifndef GOBOT_CPP_
#define GOBOT_CPP_
#include "SDL.h"
#include "gobot.h"
int gobot( int &horizontal, int &vertical, &dm )
{
//SDL_GetDesktopDisplayMode(0, &dm);
horizontal = dm->w;
vertical = dm->h;
return 0;
}
//cout<<"Resolution: x = "<__
#ifndef GOBOT_H_
#define GOBOT_H_
#include"SDL.h"
int SDL_GetDesktopDisplayMode(int displayIndex, SDL_DisplayMode * dm);
int gobot(int horizontal, int vertical, SDL_DisplayMode * dm);
#endif /* GOBOT_H_ */
error: cannot convert 'SDL_DisplayMode' to 'SDL_DisplayMode*' for
argument '3' to 'int gobot(int, int, SDL_DisplayMode*)'
gobot(horizontal, vertical, dm);*
Thanks
_______________________________________________
SDL mailing list
http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org
_________________________________________________
SDL mailing list
http://lists.libsdl.org/listinfo.cgi/sdl-libsdl.org
speartip
2017-02-09 00:08:49 UTC
Permalink
Deployed with changes; errors persistent:


Code:

horizontal = 0; vertical = 0;
SDL_DisplayMode dm;
cout<<"Gobot call:";
gobot(&horizontal,&vertical, &dm);





Code:

#include"SDL.h"

int SDL_GetDesktopDisplayMode(int displayIndex, SDL_DisplayMode * dm);
int gobot( int * horizontal, int * vertical, SDL_DisplayMode * dm);





Code:

#include "SDL.h"
#include "gobot.h"


int gobot( int * horizontal, int* vertical, &dm )
{
//SDL_GetDesktopDisplayMode(0, &dm);
*horizontal = dm->w;
*vertical = dm->h;
return 0;
}




error:

Code:

.\src\gobot.cpp:15:45: error: 'dm' has not been declared
int gobot( int * horizontal, int* vertical, dm )
^
..\src\gobot.cpp: In function 'int gobot(int*, int*, int)':
..\src\gobot.cpp:18:18: error: 'dm' was not declared in this scope
* horizontal = dm->w;
Brian Puthuff
2017-02-09 00:24:45 UTC
Permalink
int gobot( int * horizontal, int* vertical, &dm )

{
//SDL_GetDesktopDisplayMode(0, &dm);
*horizontal = dm->w;
*vertical = dm->h;
return 0;
}

Should be:

int gobot( int * horizontal, int* vertical, *SDL_DisplayMode* dm* )
{
//SDL_GetDesktopDisplayMode(0, &dm);
*horizontal = dm->w;
*vertical = dm->h;
return 0;
}

That third argument is incorrect on that first version. The definition
arguments need to match the declaration arguments. That third argument is a
pointer to a structure. The only time you pass &dm is when you actually
call the function. Not during declaration and definition.


On Feb 8, 2017 4:08 PM, "speartip" <***@fastmail.com> wrote:

Deployed with changes; errors persistent:




Code:


horizontal = 0; vertical = 0;

SDL_DisplayMode dm;
cout<<"Gobot call:";
gobot(&horizontal,&vertical, &dm);







Code:


#include"SDL.h"

int SDL_GetDesktopDisplayMode(int displayIndex, SDL_DisplayMode * dm);
int gobot( int * horizontal, int * vertical, SDL_DisplayMode * dm);







Code:


#include "SDL.h"
#include "gobot.h"


int gobot( int * horizontal, int* vertical, &dm )

{
//SDL_GetDesktopDisplayMode(0, &dm);
*horizontal = dm->w;
*vertical = dm->h;
return 0;
}




error:



Code:


.\src\gobot.cpp:15:45: error: 'dm' has not been declared
int gobot( int * horizontal, int* vertical, dm )
^
..\src\gobot.cpp: In function 'int gobot(int*, int*, int)':
..\src\gobot.cpp:18:18: error: 'dm' was not declared in this scope
* horizontal = dm->w;
speartip
2017-02-09 15:36:09 UTC
Permalink
Thank you Brian this is what it should have been. Always match your declarations and definitions!

Should be:

Code:

int gobot( int * horizontal, int* vertical, [b]SDL_DisplayMode* dm[/b] )




Works fine now. I did revert back to using pass by reference which simplified things a bit even though I know pointers are perfectly valid. So by using &var I could change the val in the subroutine without making a copy and keep the most up to date version in main.

Thank you![/code]
speartip
2017-02-09 15:40:05 UTC
Permalink
whooops


Code:


int gobot( int &horizontal, &vertical, SDL_DisplayMode * dm)
speartip
2017-02-09 15:42:50 UTC
Permalink
Thank you Brian this is what it should have been. Always match your declarations and definitions!

Should be:
Code:

int gobot( int horizontal, int vertical, SDL_DisplayMode* dm )


Works fine now. I did revert back to using pass by reference which simplified things a bit even though I know pointers are perfectly valid. So by using &var I could change the val in the subroutine without making a copy and keep the most up to date version in main.

Thank you![/code]
speartip
2017-02-09 15:47:17 UTC
Permalink
Thanks for solving that so quickly.ST

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