OpenGL and Cygwin

[Andre Bleau]

suresh at research dot att dot com wrote:

>As per Andre's suggestion, i compiled and ran the attached program. Below
>are the outputs under different system settings:
>
>All programs run from tcsh inside cygwin. My LD_LIBRARY_PATH also had my
>current dir, because I had the nvidia glut32.dll and glut32.lib files in
>it (which work when compiled with visual C++ on a different machine - I
>tried one of their demos)

Forget about LD_LIBRARY_PATH; it is not used by cygwin.


>This was the first run, just from scratch with no extra parameters.
>
>----------------------------------------------------------------------
>[Root@euclid ~/src]$ g++ -o helloglut opengltest.c -lglut32 -lglu32 -
>lopengl32
>/tmp/ccwy9vdk.o(.text+0xe):opengltest.c: undefined reference to `_glClear'
>/tmp/ccwy9vdk.o(.text+0x4c):opengltest.c: undefined reference to
>`_glutInit'
>/tmp/ccwy9vdk.o(.text+0x58):opengltest.c: undefined reference to
>`_glutCreateWin
>dow'
>/tmp/ccwy9vdk.o(.text+0x64):opengltest.c: undefined reference to
>`_glutDisplayFu
>nc'
>/tmp/ccwy9vdk.o(.text+0x69):opengltest.c: undefined reference to
>`_glutMainLoop'
>
>collect2: ld returned 1 exit status
>---------------------------------------------------------------------

The error messages above make it clear: you are using the wrong headers. 
Cygwin's OpenGL headers would have generated messages like:

$ g++ helloGlut.c -o helloGlut
/cygdrive/c/DOCUME~1/bleau/LOCALS~1/Temp/cc99dyy4.o(.text+0xe):helloGlut.c: 
unde
fined reference to `_glClear@4'
/cygdrive/c/DOCUME~1/bleau/LOCALS~1/Temp/cc99dyy4.o(.text+0x50):helloGlut.c: 
und
efined reference to `_glutInit@8'
/cygdrive/c/DOCUME~1/bleau/LOCALS~1/Temp/cc99dyy4.o(.text+0x5f):helloGlut.c: 
und
efined reference to `_glutCreateWindow@4'
/cygdrive/c/DOCUME~1/bleau/LOCALS~1/Temp/cc99dyy4.o(.text+0x6e):helloGlut.c: 
und
efined reference to `_glutDisplayFunc@4'
/cygdrive/c/DOCUME~1/bleau/LOCALS~1/Temp/cc99dyy4.o(.text+0x76):helloGlut.c: 
und
efined reference to `_glutMainLoop@0'
collect2: ld returned 1 exit status

Notice the @4, @8, and @0 after the names.

You said in a previous message that you downloaded headers from NVDIA's 
site. If you are using these, that's the source of the problem. They are 
incompatible with gcc and g++ because they do not specify the right calling 
convention.

My advice: ditch those headers and use the ones from Cygwin's OpenGL 
package, or the ones from Cygwin's w32api package.

Alternative: modify NVDIA's headers to specify the right calling convention 
by adding

__attribute__ ((__stdcall__))

to the declaration of the functions. However, if you choose that path, do 
not expect anymore help from me; I am not going to support people who 
replace headers from Cygwin packages with headers from third parties. You 
would have to go to NVDIA's site for support.



André Bleau, Cygwin's OpenGL package maintainer.

Please address all questions and problem reports about Cygwin's OpenGL 
package to cygwin@cygwin.com . 


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