glshaderSource needs a GLchar** and all I get from cast(char[]) read(filename) is a single *

How do I get this extra pointer ? :D

The C code is:

char *file;
shader = glCreateShader(GL_FRAGMENT_SHADER);
file = textFileRead("program.frag");
const char * filep = file;
glShaderSource(f, 1, &filep,NULL);
free(filep);

my D attempt:

char[] file;
GLuint shader;
shader=glCreateShader(GL_FRAGMENT_SHADER);
file=cast(char[])read(`program.frag`);
glShaderSource(f, 1, cast(char **) toStringz(file),null);
//let gc collect file

Error: Access Violation :)

On Thu, 30 Oct 2008 20:44:06 +0100, Saaa <empty@needmail.com> wrote:

> glshaderSource needs a GLchar** and all I get from cast(char[])
> read(filename) is a single *
>
> How do I get this extra pointer ? :D
>
> The C code is:
>
> char *file;
> shader = glCreateShader(GL_FRAGMENT_SHADER);
> file = textFileRead("program.frag");
> const char * filep = file;
> glShaderSource(f, 1, &filep,NULL);
> free(filep);
>
> my D attempt:
>
> char[] file;
> GLuint shader;
> shader=glCreateShader(GL_FRAGMENT_SHADER);
> file=cast(char[])read(`program.frag`);
> glShaderSource(f, 1, cast(char **) toStringz(file),null);
> //let gc collect file
>
> Error: Access Violation :)

I believe this should work:

	char[] file;
	file = toStringz(read("program.frag"));
	glShaderSource(f, 1, &file, null);

What your program does, is treat the first chars of toStringz(file)
as a pointer, then wander off wildly in that direction.

A more D-like way of doing it would possibly be:

	char[] file;
	file = read("program.frag");
	glShaderSource(f, 1, &file.ptr, &file.length);

-- 
Simen

On Thu, 30 Oct 2008 20:57:56 +0100, Simen Kjaeraas <simen.kjaras@gmail.com> wrote:

> A more D-like way of doing it would possibly be:
>
> 	char[] file;
> 	file = read("program.frag");
> 	glShaderSource(f, 1, &file.ptr, &file.length);
>

Scratch this last part. I'd hoped it worked, but ptr and length aren't lvalues, so no can do.

-- 
Simen

Saaa wrote:
> glshaderSource needs a GLchar** and all I get from cast(char[]) read(filename) is a single *
> 
> How do I get this extra pointer ? :D
> 
> The C code is:
> 
> char *file;
> shader = glCreateShader(GL_FRAGMENT_SHADER);
> file = textFileRead("program.frag");
> const char * filep = file;
> glShaderSource(f, 1, &filep,NULL);
> free(filep);
> 
> my D attempt:
> 
> char[] file;
> GLuint shader;
> shader=glCreateShader(GL_FRAGMENT_SHADER);
> file=cast(char[])read(`program.frag`);
> glShaderSource(f, 1, cast(char **) toStringz(file),null);
> //let gc collect file
> 
> Error: Access Violation :)
> 
> 

Assuming the C code works, here's what you do in D.

GLuint shader;
shader=glCreateShader(GL_FRAGMENT_SHADER);
char[] file=cast(char[])read(`program.frag`);
char* filep = toStringz(file);
glShaderSource(f, 1, &filep,null);

>
> Assuming the C code works, here's what you do in D.
>
> GLuint shader;
> shader=glCreateShader(GL_FRAGMENT_SHADER);
> char[] file=cast(char[])read(`program.frag`);
> char* filep = toStringz(file);
> glShaderSource(f, 1, &filep,null);
>

erm.. ok, thanks :)
Thought I tried this already.
But, how is filep now an char** ?

Saaa wrote:
>>
>> Assuming the C code works, here's what you do in D.
>>
>> GLuint shader;
>> shader=glCreateShader(GL_FRAGMENT_SHADER);
>> char[] file=cast(char[])read(`program.frag`);
>> char* filep = toStringz(file);
>> glShaderSource(f, 1, &filep,null);
>>
> 
> erm.. ok, thanks :)
> Thought I tried this already.
> But, how is filep now an char** ? 

It's not filep that's a char**, it's &filep. You're taking the address of a pointer, so you end up with a pointer to a pointer.

If this code doesn't work, then something else is the matter.

On Thu, 30 Oct 2008 21:02:41 +0100, Simen Kjaeraas <simen.kjaras@gmail.com> wrote:

> On Thu, 30 Oct 2008 20:57:56 +0100, Simen Kjaeraas <simen.kjaras@gmail.com> wrote:
>
>> A more D-like way of doing it would possibly be:
>>
>> 	char[] file;
>> 	file = read("program.frag");
>> 	glShaderSource(f, 1, &file.ptr, &file.length);
>>
>
> Scratch this last part. I'd hoped it worked, but ptr and length aren't lvalues, so no can do.
>

BTW, shouldn't these be reference return values now (dmd v2.020)?

-- 
Simen

No no, it works.
I always read &x as the location of x in memory, which as a whole is
ofcourse a pointer :/
My bad.. too long since using them.

>
> It's not filep that's a char**, it's &filep. You're taking the address of a pointer, so you end up with a pointer to a pointer.
>
> If this code doesn't work, then something else is the matter.

Still D1 here.. :)

>>
>
> BTW, shouldn't these be reference return values now (dmd v2.020)?
>
> -- 
> Simen

On Fri, Oct 31, 2008 at 5:20 AM, Saaa <empty@needmail.com> wrote:
>>
>> Assuming the C code works, here's what you do in D.
>>
>> GLuint shader;
>> shader=glCreateShader(GL_FRAGMENT_SHADER);
>> char[] file=cast(char[])read(`program.frag`);
>> char* filep = toStringz(file);
>> glShaderSource(f, 1, &filep,null);
>>
>
> erm.. ok, thanks :)
> Thought I tried this already.
> But, how is filep now an char** ?

It isn't filep is still char*.  But &filep is a pointer to filep,
which is a (char*)*.
You realize that if you have TypeX x, then  typeof(&x) is TypeX*, right?

--bb