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Xarragon
04-05-2006, 03:59 PM
Hello, fellow Linux OpenGL coders.
All of a sudden my texture loading code stopped working on my primary workstation, an amd64 system running debian testing ('etch') in i386 mode. I'm using Nvidias lastest driver, built as a custom driver package. GLU package seems to be libglu1-xorg (at least that is what is installed).

The code itself has worked without a hitch for a long time (I didn't even touch it when it broke). It runs fine on my laptop (Thinkpad X41 running Ubuntu Breezy). Other OpenGL applications seems to be running fine, including Blender 3D and Enemy Territory.

Here is the error output:


TextureManager: Request for "../data/ui/background.tga".
TextureManager: Loading new texture from disk.
An TGA image was loaded successfully.
compression: 0, width: 512 height: 512
bpp: 24
size: 786432 bytes, bytesPerPixel: 3
numChannels: 3
New texture ID is: 3214180648.
Building mipmaps.

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1222743808 (LWP 13277)]
0xb7bfff16 in strtof_l () from /lib/tls/libc.so.6
(gdb) bt
#0 0xb7bfff16 in strtof_l () from /lib/tls/libc.so.6
#1 0xb7bfd1e8 in __strtod_internal () from /lib/tls/libc.so.6
#2 0xb7ebd6ad in __gluTessErrorString () from /usr/X11R6/lib/libGLU.so.1
#3 0x00000000 in ?? ()
(gdb)And here is the code itself:


bool GLTexture::load (const Image &img, const TextureParameters &prm)
{
GLuint newid;

glGenTextures(1, &newid);
if (newid == 0) return false;

printf("New texture ID is: %u.\n", newid);

glBindTexture(GL_TEXTURE_2D, newid);
GLuint err = glGetError();
if (glGetError() != GL_NO_ERROR)
System::warning("GLTexture: An OpenGL error has been detected.(1)");

glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, prm.getGLMinFilter());
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, prm.getGLMagFilter());
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, prm.getGLWrapS());
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, prm.getGLWrapT());

err = glGetError();
if (err != GL_NO_ERROR)
System::warning("GLTexture: An OpenGL error has been detected.(2): %d", err);

GLenum format = 0;
if (img.getFormat() == Image::RGB) {
format = GL_RGB;
} else {
format = GL_RGBA;
}

glTexImage2D(GL_TEXTURE_2D, 0, format, img.getWidth(), img.getHeight(), 0, format, GL_UNSIGNED_BYTE, img.getData());

err = glGetError();
if (err != GL_NO_ERROR)
System::warning("GLTexture: An OpenGL error has been detected.(3): %d", err);

if (prm.isMipMapped()) {
printf("Building mipmaps.\n");
if (gluBuild2DMipmaps(GL_TEXTURE_2D, format, img.getWidth(), img.getHeight(), format, GL_UNSIGNED_BYTE, img.getData()) != 0) {
System::warning("GLTexture: Mipmap creation failed.");
}
}

if (glGetError() != GL_NO_ERROR)
System::warning("GLTexture: An OpenGL error has been detected.(4)");

// We only load the id when everything has worked out ok.
// This way we can give a 'Strong Guarantee'.
id = newid;

return true;
}Some oddities I've noticed include the large OpenGL texture ID, which is also completely random on each iteration. The ID's usually started on 1 and went on upwards. This MIGHT be a new implementation that assigns the ID's in a non-linear manner, I suspect.

I also found some people having similar difficulties (also debian):
Armagetron forums discussion (http://forums.armagetronad.net/viewtopic.php?t=2119&sid=7dfc485bf401b0227b50c0d7b907db51)

Any help resolving this issue would be greatly appreciated, I'm starting to miss my good, old Slackware again...

Addendum: The problem persists despite an upgrade to the unstable version of debian (still exactly the same package for libglu1-xorg). Full recompile/rebuild performed to no avail.

Second addendum: It would seem the problem is with glGenTextures(). I modified the code to always initialize the variable newid to zero (good practice). And voila, glGenTextures() does not modify it at all...

Xarragon
04-06-2006, 06:16 AM
This issue has been resolved. The cause was incorrect linkage, since I did not have the package called nvidia-glx-dev installed on my system.

memfr0b in the ##opengl IRC channel on freenode was patient enough to listen to my ramblings, and soon had it solved. Many thanks to you!

He suggested that what happened was that I linked against the Mesa gl implementation on build time, but later, at run-time, the Nvidia gl library was loaded instead.

So, if you have this problem and uses Nvidia drivers on debian, make sure you have the -dev package as well as the regular glx package. Most distors don't really split it up like this, but uses a single package for both headers and library files, in which case the issue would probably not arise in the first place.

gemelli_d
04-06-2006, 08:23 AM
it is not related but just to save some time, you can skip the glTexImage2D when successfuly using gluBuild2DMipmaps.

Xarragon
04-06-2006, 09:24 AM
Thanks for the pointer. memfr0b acctually pointed out the very same thing when he helped me with my problems. The whole texture class is a chunky old beast that has just "always worked", but a cleanup of it IS scheduled. Someday. :-)