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digitalmars.D.learn - X11 XSynchronize() definition in D

reply "andrea9940" <no mail.plz> writes:
Hi, I'm working with the X11 library available from 
https://github.com/D-Programming-Deimos/libX11
If I try to call XSynchronize(display, True) the compilation 
fails with "Error: function deimos.X11.Xlib.XSynchronize 
(_XDisplay*) is not callable using argument types (_XDisplay*, 
int)"

I am sure the arguments are correct (see http://goo.gl/8Hzn8s for 
example) so I think there is a conversion problem between the C 
and D definition of the function:

--- Xlib.h
extern int (*XSynchronize(
     Display*		/* display */,
     Bool		/* onoff */
))(
     Display*		/* display */
);

--- Xlib.d
extern int function(
     Display*            /* display */,
     Bool                /* onoff */
)XSynchronize(
     Display*            /* display */
);


Also I can't understand why the C version is not "extern int 
XSynchronize(Display*,
     Bool);" which would be the simplest definition.
Aug 06 2013
next sibling parent reply "bearophile" <bearophileHUGS lycos.com> writes:
andrea9940:


 extern int function(
     Display*            /* display */,
     Bool                /* onoff */
 )XSynchronize(
     Display*            /* display */
 );


Try extern(C)?

Bye,
bearophile
Aug 06 2013
parent "andrea9940" <no mail.plz> writes:
On Tuesday, 6 August 2013 at 08:21:26 UTC, bearophile wrote:

 Try extern(C)?


It's not a linkage error, it's a syntax one
Aug 06 2013
prev sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 08/06/2013 01:01 AM, andrea9940 wrote:


 Hi, I'm working with the X11 library available from
 https://github.com/D-Programming-Deimos/libX11
 If I try to call XSynchronize(display, True) the compilation fails with
 "Error: function deimos.X11.Xlib.XSynchronize (_XDisplay*) is not
 callable using argument types (_XDisplay*, int)"

 I am sure the arguments are correct (see http://goo.gl/8Hzn8s for
 example) so I think there is a conversion problem between the C and D
 definition of the function:

 --- Xlib.h
 extern int (*XSynchronize(
      Display*        /* display */,
      Bool        /* onoff */
 ))(
      Display*        /* display */
 );


I have written the following stubs for C:

typedef void Display;
typedef int Bool;

extern int (*XSynchronize(
     Display*        /* display */,
     Bool        /* onoff */
))(
     Display*        /* display */
);

typedef int(*PreviousAfterFunction)(Display*);

int previous_after_foo(Display* display)
{
     return 0;
}

PreviousAfterFunction XSynchronize(Display* display, Bool onoff)
{
     return &previous_after_foo;
}

int main()
{
     int (*paf)(Display*) = XSynchronize(0, 1);
     paf(0);
}

And then I have written the direct translation in D, which works as well:

struct Display
{}

alias PreviousAfterFunction = int function(Display*);

int previousAfterFoo(Display *)
{
     return 0;
}

PreviousAfterFunction XSynchronize(Display*, bool)
{
     return &previousAfterFoo;
}

void main()
{
     PreviousAfterFunction paf = XSynchronize(null, 1);
     paf(null);
}


 --- Xlib.d
 extern int function(
      Display*            /* display */,
      Bool                /* onoff */
 )XSynchronize(
      Display*            /* display */
 );


It looks like Xlib.d got it backwards: XSynchronize takes two parameters 
and returns a function pointer that takes a single parameter. It should 
be the following:

int function(Display*) XSynchronize(Display*, bool);


 Also I can't understand why the C version is not "extern int
 XSynchronize(Display*,
      Bool);" which would be the simplest definition.


That's different. That would be a function taking two parameters and 
returning int. However, XSynchronize takes two parameters and return a 
function pointer (that takes one parameter and returns an int).

Ali
Aug 06 2013
next sibling parent reply David <d dav1d.de> writes:
 struct Display
 {}


D supports opaque structs/pointers

struct Display;

Now Display has to be used as pointer only or the compiler complains
e.g. about

Display display;
Aug 06 2013
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 08/06/2013 03:22 AM, David wrote:>> struct Display

 {}


 D supports opaque structs/pointers

 struct Display;

 Now Display has to be used as pointer only or the compiler complains
 e.g. about

 Display display;


Yes and I am sure that is how Xlib.d has it.

However, remembering a limitation that we have discovered a couple of 
weeks ago, I intentionally did not make it opaque, in case somebody 
would try toString() on it:

   http://forum.dlang.org/post/ksc2ln$f1i$1 digitalmars.com

I have been to lazy to bring this topic up on the main newsgroup before 
opening an enhancement request.

Ali
Aug 06 2013
parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 08/06/2013 08:46 AM, Ali Çehreli wrote:


 On 08/06/2013 03:22 AM, David wrote:>> struct Display
  >> {}
  >
  > D supports opaque structs/pointers
  >
  > struct Display;
  >
  > Now Display has to be used as pointer only or the compiler complains
  > e.g. about
  >
  > Display display;

 Yes and I am sure that is how Xlib.d has it.

 However, remembering a limitation that we have discovered a couple of
 weeks ago, I intentionally did not make it opaque, in case somebody
 would try toString() on it:


I am confused and being confusing... I think nobody should apply 
toString() on an opaque type as it is supposed to dereference the actual 
object.


    http://forum.dlang.org/post/ksc2ln$f1i$1 digitalmars.com


I will continue on that thread.

Ali
Aug 06 2013
prev sibling parent "andrea9940" <no mail.plz> writes:
 Ali Çehreli
Thank you for the explanation. I'll send a pull request to fix 
Xlib.d
Aug 06 2013