Mailing-List: contact cygwin-help AT sourceware DOT cygnus DOT com; run by ezmlm
Sender: cygwin-owner AT sources DOT redhat DOT com
Message-Id: <4.3.2.7.0.20000717130520.00aedde8@courriel.polymtl.ca>
Date: Mon, 17 Jul 2000 13:05:26 -0400
To: cygwin AT sources DOT redhat DOT com
From: Andre Bleau <andre DOT bleau AT courriel DOT polymtl DOT ca>
Subject: glGetString and Open GL link errors: Answer
Cc: dj AT delorie DOT com, jason AT whizzird DOT net
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"; format=flowed
Content-Transfer-Encoding: 8bit

Hi there.

I am the "maintainer" for the opengl package.

1-	There is a faulty line in the /usr/local/include/GL/gl.h file. Replace 
the line:

extern const GLubyte * glGetString (GLenum name);
	to read
extern const APIENTRY GLubyte * glGetString (GLenum name);


2-	If you still have link errors, e.g.:

main.o(.text+0x31):main.c: undefined reference to `glColor3f AT 12'

then you are probably using the wrong include files. If you installed .h 
files that you found somewhere else in /usr/include/GL, these would mask 
the ones that the package installs. Rename /usr/include/GL to 
/usr/include/oldGL so that the compiler sees the files in 
/usr/local/include/GL. This should do the trick.

I don't have my own ftp server, so I uploaded a fixed tar ball to DJ 
Delorie. I hope he will make it available as a contrib or in the main 
distribution.

Now, I want to stress that my own contribution is _very_ small. Here is 
some background:

1-	M$ provides glu32.dll and opengl32.dll with NT 4.0 and Windows 2000. I 
don't know about Windows 95/98.

2-	Cygwin 1.1.2 provides libglut32.a, libglu32.a and libopengl32.a in 
/usr/lib, but no .h files and no glut32.dll. I guess that the .a files were 
built using dlltool from the dll files, not from sources.

3-	If you get .h files from OpenGL and GLUT sites, you are not able to link 
with cygwin's .a files. The linker will complain, for example, that it 
cannot find glColor3f AT 12 while your code is calling glColor3f . This is 
because the .a files contain functions that are meant to be linked with 
MSVC or Borland C, not with gcc. gcc uses a different API by default; you 
have to tell it explicitly when you called M$ API functions.

4-	After trying for days to solve that problem and profering a lot of 
english four letter words and french profanities, I figured it out with the 
help of Jérôme Benoit, and I prepared modified .h files that declare Open 
GL, GLU and GLUT functions with the right API. I was able to build GLUT and 
Open GL programs; life was wonderfull again.

5-	I thought there might be other people out there, bothered by the same 
problem, so I packaged my modified .h files with a glut32.dll from the GLUT 
site (http://reality.sgi.com/mjk_asd/glut3/glut3.html). I added another 
static library for the GLUI package, which I had built from sources and 
found very usefull; see http://www.cs.unc.edu/~rademach/glui/ . Upon DJ's 
suggestion, this package, opengl-1.2.1-1, was uploaded to his site and he 
placed it in the contrib directory, and later in the main distribution.

6-	I discovered a flawed line in gl.h and received a few emails about it. 
See above.

7-	I realized that M$ was not providing Open GL 1.2.1, but Open GL 1.1.0.

8-	I made a new package, opengl-1.1.0-1, with a corrected README and gl.h 
file and uploaded to DJ's site. Hope you will be able to use it soon.

Please realize that this package only enables you to link with M$ Open GL 
and GLU dll. If these are not provided by your OS, there is nothing I can 
do about it.

Regards,

André Bleau, ing., analyste
bleau AT courriel DOT polymtl DOT ca

Département de génie électrique et         Electric Engineering and
de génie informatique                      Computer Engineering department
École Polytechnique de Montréal            Montreal Polytechnic School


--
Want to unsubscribe from this list?
Send a message to cygwin-unsubscribe AT sourceware DOT cygnus DOT com