Which dylib in OpenGL framework gets linked? (simple glut ex)

johnMG

Unregistered

Post: #1

Oct 21, 2003 — 07:50 AM

This is my first post here, and I'm also just getting started with OSX and Obj-C. :)

I made a small glut example program by:
-- using PB to create a Cocoa app,
-- added the GLUT and OpenGL frameworks to the project,
-- renamed main.m to main.c, wiped out what was in there:

Code:

#import <Cocoa/Cocoa.h>

int main(int argc, const char *argv[])

{

    return NSApplicationMain(argc, argv);

}

and put in this:

Code:

#include <OpenGL/gl.h>

#include <OpenGL/glu.h>

#include <GLUT/glut.h>

void initGL();

void drawGLScene();

void resizeGLScene( int width, int height );

int main(int argc, char *argv[])

{

    glutInit( &argc, argv );

    glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );

    glutInitWindowSize( 400, 600 );

    glutInitWindowPosition( 100, 200 );

    glutCreateWindow( argv[0] );

    initGL();

    glutDisplayFunc( drawGLScene );

    glutReshapeFunc( resizeGLScene );

    glutMainLoop();

    return 0;

}

void initGL()

{

    glShadeModel( GL_SMOOTH );

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    glClearDepth(1.0f);

    glEnable( GL_DEPTH_TEST );

    glDepthFunc( GL_EQUAL );

    glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );

}

void drawGLScene()

{

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();

}

void resizeGLScene( int width, int height )

{

    if ( height == 0 ) height = 1;

    if ( width == 0 )  width = 1;

    glViewport( 0, 0, width, height );

    glMatrixMode( GL_PROJECTION );

    glLoadIdentity();

    gluPerspective(

        45.0,

        (float)width / (float)height,

        1.0,

        10.0 );

    glMatrixMode( GL_MODELVIEW );

    glLoadIdentity();

}

and after a 'clean', it built and ran fine.

(Hmm.. Is that the correct way to set up a program using glut?)

My question is, exactly which library am I linking to?

Looking in /System/Library/Frameworks/OpenGL.framework, there's a Mach-O dylib named OpenGL, but also in a Libraries subdirectory, there's libGL.dylib and libGLU.dylib.

How can I tell which library (libGL.dylib or OpenGL) I'm linking to? (No ldd command here. :) )

Why is the file OpenGL named without the .dylib extension?

Steven

Member

Posts: 370
Joined: 2002.04

Post: #2

Oct 21, 2003 — 08:40 AM

Read up on the manpage for otool - it'll tell you what libraries you're using.

Did you ever wonder why we had to run for shelter when the promise of a brave new world unfurled beneath the clear blue sky?

johnMG

Unregistered

Post: #3

Oct 21, 2003 — 11:01 AM

Thanks Steven. Looks like the most common use of otool for app devs is otool -L executable which is very similar to ldd.

OneSadCookie

Luminary

Posts: 5,131
Joined: 2002.04

Post: #4

Oct 21, 2003 — 12:38 PM

You're linking to the framework, not the individual dylibs. I suspect (though I don't know) that the framework links to the dylibs, but the OpenGL framework is unusual in even having any dylibs.

johnMG

Unregistered

Post: #5

Oct 21, 2003 — 05:16 PM

> but the OpenGL framework is unusual in even having any dylibs.

Ahh,.. I hadn't noticed that. I see that there's only four that contain dylibs:
ApplicationServices.framework
CoreServices.framework
JavaVM.framework
OpenGL.framework

johnMG

Unregistered

Post: #6

Oct 21, 2003 — 08:24 PM

Ah. Ok. The OpenGL Mach-O has a bunch of CGL stuff in it. (Hmm. Interesting and possibly relevant article: http://developer.apple.com/qa/qa2001/qa1269.html )

Code:

[john /System/Library/Frameworks/OpenGL.framework/Versions/A]$ otool -vT OpenGL

OpenGL:

Table of contents (29 entries)

module name      symbol name

cgl_format.o     _CGLChoosePixelFormat

cgl_drawable.o   _CGLClearDrawable

cgl_context.o    _CGLCopyContext

cgl_context.o    _CGLCreateContext

cgl_format.o     _CGLDescribePixelFormat

cgl_renderer.o   _CGLDescribeRenderer

cgl_context.o    _CGLDestroyContext

cgl_format.o     _CGLDestroyPixelFormat

cgl_renderer.o   _CGLDestroyRendererInfo

cgl_state.o      _CGLDisable

cgl_state.o      _CGLEnable

cgl_error.o      _CGLErrorString

cgl_swap.o       _CGLFlushDrawable

cgl_context.o    _CGLGetNextContext

cgl_drawable.o   _CGLGetOffScreen

cgl_option.o     _CGLGetOption

cgl_state.o      _CGLGetParameter

cgl_drawable.o   _CGLGetSurface

cgl_version.o    _CGLGetVersion

cgl_context.o    _CGLGetVirtualScreen

cgl_state.o      _CGLIsEnabled

cgl_renderer.o   _CGLQueryRendererInfo

cgl_drawable.o   _CGLSetFullScreen

cgl_drawable.o   _CGLSetOffScreen

cgl_option.o     _CGLSetOption

cgl_state.o      _CGLSetParameter

cgl_drawable.o   _CGLSetSurface

cgl_context.o    _CGLSetVirtualScreen

cgl_drawable.o   _CGLUpdateContext

whereas, ''otool -vT Libraries/libGL.dylib" shows me all the OpenGL functions that I expect to see (a long list including glVertex3*(), etc.).

Also, the OpenGL Mach-O relies on libGL.dylib:

Code:

[john /System/Library/Frameworks/OpenGL.framework/Versions/A]$ otool -L OpenGL

OpenGL:

        /System/Library/Frameworks/OpenGL.framework/Versions/A/OpenGL

 (compatibility version 1.0.0, current version 1.0.0)

        /System/Library/Frameworks/ApplicationServices.framework/Versions/A/ApplicationServices

 (compatibility version 1.0.0, current version 18.0.0)

        /System/Library/Frameworks/IOKit.framework/Versions/A/IOKit

 (compatibility version 1.0.0, current version 120.4.0)

        /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation

 (compatibility version 150.0.0, current version 263.5.0)

        /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGLU.dylib

 (compatibility version 1.0.0, current version 1.0.0)

        /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib

 (compatibility version 1.0.0, current version 1.0.0)

        /usr/lib/libSystem.B.dylib

 (compatibility version 1.0.0, current version 63.0.0)

[john /System/Library/Frameworks/OpenGL.framework/Versions/A]$ otool -L Libraries/libGL.dylib 

Libraries/libGL.dylib:

        /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib

 (compatibility version 1.0.0, current version 1.0.0)

        /usr/lib/libSystem.B.dylib

 (compatibility version 1.0.0, current version 63.0.0)

anarchie

Unregistered

Post: #7

Oct 22, 2003 — 06:06 AM

FWIW, OpenGL.framework/OpenGL has no extension because it is the convention for frameworks, much the way Foo.app/Contents/MacOS/Foo has no extension either.

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