OpenGL/lwjgl 纹理创建 sigsegv

Question

Im trying to create a simple OpenGL program using lwjgl and I'm currently stuck at creating a texture to render.

The error I'm getting is a segmentation fault:

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007fff6c894ab6, pid=18463, tid=775
#
# JRE version: OpenJDK Runtime Environment (14.0.1+7) (build 14.0.1+7)
# Java VM: OpenJDK 64-Bit Server VM (14.0.1+7, mixed mode, sharing, tiered, compressed oops, g1 gc, bsd-amd64)
# Problematic frame:
# C  [libGLImage.dylib+0x11ab6]  _Z15glgConvertTo_32I23GLGConverter_RGB8_ARGB8L9GLGMemory1EEvPK15GLGOperationRecPK15GLDPixelModeRec+0x59
#
# No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# If you would like to submit a bug report, please visit:
#   https://bugreport.java.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#

Machine info:

Host: iMac16,2 x86_64 2800 MHz, 4 cores, 8G, Darwin 20.2.0
Time: Wed Jun  2 23:49:46 2021 CEST elapsed time: 178 seconds (0d 0h 2m 58s)

Problematic JVM thread stack:

Stack: [0x00007ffee5272000,0x00007ffee5a72000],  sp=0x00007ffee5a6de10,  free space=8175k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
C  [libGLImage.dylib+0x11ab6]  _Z15glgConvertTo_32I23GLGConverter_RGB8_ARGB8L9GLGMemory1EEvPK15GLGOperationRecPK15GLDPixelModeRec+0x59
C  [libGLImage.dylib+0x6227]  glgProcessPixelsWithProcessor+0xdf4
C  [AppleIntelBDWGraphicsGLDriver+0x13500]  glrWriteTextureData+0x1438
C  [GLEngine+0x189f7]  glTexImage2D_Exec+0x52b
C  [libGL.dylib+0x3195]  glTexImage2D+0x37
C  [liblwjgl_opengl.dylib+0xb22e]
j  org.lwjgl.opengl.GL11C.nglTexImage2D(IIIIIIIIJ)V+0
j  org.lwjgl.opengl.GL11C.glTexImage2D(IIIIIIIILjava/nio/ByteBuffer;)V+17
j  org.lwjgl.opengl.GL11.glTexImage2D(IIIIIIIILjava/nio/ByteBuffer;)V+14
j  rendering.Window.render()V+420
j  rendering.Window.loop()V+8
j  rendering.Window.main([Ljava/lang/String;)V+25
v  ~StubRoutines::call_stub
V  [libjvm.dylib+0x34bbbe]  _ZN9JavaCalls11call_helperEP9JavaValueRK12methodHandleP17JavaCallArgumentsP6Thread+0x256
V  [libjvm.dylib+0x39032d]  _ZL17jni_invoke_staticP7JNIEnv_P9JavaValueP8_jobject11JNICallTypeP10_jmethodIDP18JNI_ArgumentPusherP6Thread+0x11c
V  [libjvm.dylib+0x393c10]  jni_CallStaticVoidMethod+0x1b3
C  [libjli.dylib+0x4a42]  JavaMain+0xab4
C  [libjli.dylib+0x6fb3]  __JVMInit_block_invoke+0x4b
C  [Foundation+0x4201c]  __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__+0x7
C  [Foundation+0x41f14]  -[NSBlockOperation main]+0x62
C  [Foundation+0x41ea5]  __NSOPERATION_IS_INVOKING_MAIN__+0x11
C  [Foundation+0x41156]  -[NSOperation start]+0x311
C  [Foundation+0x804d9]  __NSThreadPerformPerform+0xcc
C  [CoreFoundation+0x81a0c]  __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__+0x11
C  [CoreFoundation+0x81974]  __CFRunLoopDoSource0+0xb4
C  [CoreFoundation+0x816ef]  __CFRunLoopDoSources0+0xf8
C  [CoreFoundation+0x80121]  __CFRunLoopRun+0x37a
C  [CoreFoundation+0x7f6ce]  CFRunLoopRunSpecific+0x233
C  [libjli.dylib+0x65c1]  CreateExecutionEnvironment+0x18f
C  [libjli.dylib+0x2752]  JLI_Launch+0x54a
C  [java+0xca1]  main+0x177
C  [libdyld.dylib+0x15621]  start+0x1

And finally my piece of code that handles the texture creation:

    // texture stuff

    int texture = glGenTextures();
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texture);

    // load and generate the texture
    glTexImage2D(
            GL_TEXTURE_2D, // target
            0, // highest level of detail
            GL_RGB, // source image bytes per pixel rgb = 3
            image.getWidth(), // width
            image.getHeight(), // height
            0, // ??? must be zero
            GL_RGB, // shader texel layout
            GL_UNSIGNED_BYTE, // size of each color channel
            image.getBuffer() // the data itself, a ByteBuffer wrapping byte[12]
    );
    glGenerateMipmap(GL_TEXTURE_2D);

    // set the texture wrapping/filtering options (on the currently bound texture object)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    // toggle on to use lines
    // glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

    // use our nice shader
    glUseProgram(shaderProgram.id);

    // set uniforms after activation
    shaderProgram.setInt("tex", 0); // why zero? idk

The image class I've created works perfectly fine, the example image I used is 2 by 2 pixels and has an internal buffer of 12 bytes length, so the segvault shouldn't be caused by a too short buffer.

Answer 1

Your image size is 2x2 and the image format is RGB. Therefore the length of a line is 6 bytes. By default OpenGL assumes that the start of each row of an image is aligned to 4 bytes.

This is because the GL_UNPACK_ALIGNMENT parameter by default is 4. Since the image has 3 color channels ( GL_RGB ), and is tightly packed the size of a row of the image may not be aligned to 4 bytes.
When a RGB image with 3 color channels is loaded to a texture object and 3*width is not divisible by 4, GL_UNPACK_ALIGNMENT has to be set to 1, before specifying the texture image with glTexImage2D :

glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image.getWidth(), image.getHeight(), 
    0, GL_RGB, GL_UNSIGNED_BYTE, image.getBuffer());

Answer 2

Thanks to Rabbid76's answer and Kai Burjack's comment I got the programm working!

I had to explicitly tell OpenGL to use a one-byte alignment AND had to avoid ByteBuffer.wrap and ByteBuffer.allocate (and use ByteBuffer.allocateDirect )

Without your help I would probeably still be suffering from debugging-depression;) So thanks again for helping.