绘制太多元素时，glDrawArrays会出现段错误

编程问答 2022-04-26

问题描述

|| 我有一些简单的C ++ OpenGL ES代码，可以在运行Android的手机，运行webOS的手机以及使用SDL / OpenGL的Mac上运行。所讨论的代码只是绘制一个存储在
GLfloat
s数组中的
GL_LINE_STRIP
。这是我尝试执行的操作（版本1）： 
GLfloat array* = new GLfloat[2048];
//later... (array gets filled)
int howMany = 1024;
glVertexPointer(2,GL_FLOAT,array); checkError();
glDrawArrays(GL_LINE_STRIP,howMany); checkError();
似乎应该很简单。但是，以上代码在Android和Mac上的OpenGL驱动程序中均存在段错误（无论出于何种原因，似乎都可以在webOS上正常运行。）为避免这种情况（这是我必须做的）（版本2）： 
GLfloat array* = new GLfloat[2048];
//later... (array gets filled)
int howMany = 1024;
for (unsigned i = 0; i < howMany; i += 789) {
    glVertexPointer(2,array+i*2); checkError();
    //this is not a bug: we draw one more than we increment by,or there is a hole in the graph
    glDrawArrays(GL_LINE_STRIP,std::min(790U,howMany-i)); checkError();
}
限制一次绘制的线条数始终可以避免分段错误。 790是通过实验确定的；在791时，它在OSX上崩溃（Android可能会更高，尽管以前以前在很多版本中限制为113个……所以该数字似乎对于每个应用程序版本都是一致的，但在不同版本或平台之间并不相同。） 我的应用程序中还有很多其他GL内容，但这是一个大型应用程序，发布所有这些代码不切实际。那么，这可能导致什么呢？我应该考虑什么可能性？ 这是我尝试使用版本1时在OSX上运行并崩溃的程序的valgrind输出： 
==85414== Conditional jump or move depends on uninitialised value(s)
==85414==    at 0x1D022993: glVertexPointer_Exec (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414==    by 0x6AA59A9: glVertexPointer (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib)
==85414==    by 0x2B001: draw_elements (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x2B44C: glDrawArrays (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0xB639: GLImage::glDraw(int,int) (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0xC292: GLLabel::glDraw(int,int) (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x1AC67: RTAPlot::drawAxes(int) (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x1B30A: RTAPlot::updateGL() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x225F5: RTAPlotView::updateForeground() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x19FC4: RTAComponent::update() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x805D: AudiaApplication_private::updateGL() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x267DF: AudiaApplication::run() (in ./rta.app/Contents/MacOS/rta)
==85414==  Uninitialised value was created by a stack allocation
==85414==    at 0x1D02268F: glVertexPointer_Exec (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414== 
==85414== Conditional jump or move depends on uninitialised value(s)
==85414==    at 0x1D022E0C: glTexCoordPointer_Exec (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414==    by 0x6AA5216: glTexCoordPointer (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib)
==85414==    by 0x2B279: draw_elements (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x2B44C: glDrawArrays (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0xB639: GLImage::glDraw(int,int) (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x1AC67: RTAPlot::drawAxes(int) (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x1B30A: RTAPlot::updateGL() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x225F5: RTAPlotView::updateForeground() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x19FC4: RTAComponent::update() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x805D: AudiaApplication_private::updateGL() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x267DF: AudiaApplication::run() (in ./rta.app/Contents/MacOS/rta)
==85414==  Uninitialised value was created by a stack allocation
==85414==    at 0x1D022A6B: glTexCoordPointer_Exec (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414== 
==85414== Invalid read of size 8
==85414==    at 0x1D0B9166: gleRunVertexSubmitImmediate (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414==    by 0x1D0B84FB: gleLLVMArrayFunc (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414==    by 0x1D0A14F2: gleDrawArraysOrElements_ExecCore (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414==    by 0x1D0A2A04: glDrawElements_IMM_Exec (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Resources/GLEngine.bundle/GLEngine)
==85414==    by 0x6AA304F: glDrawElements (in /System/Library/Frameworks/OpenGL.framework/Versions/A/Libraries/libGL.dylib)
==85414==    by 0x2B2DB: draw_elements (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x2B44C: glDrawArrays (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x1FEF6: RTAPlotCanvas::drawLineStrip(float*,unsigned int) (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x1E91A: RTAPlotCanvas::updateGL() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x1B318: RTAPlot::updateGL() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x225F5: RTAPlotView::updateForeground() (in ./rta.app/Contents/MacOS/rta)
==85414==    by 0x19FC4: RTAComponent::update() (in ./rta.app/Contents/MacOS/rta)
==85414==  Address 0xc0000000 is not stack\'d,malloc\'d or (recently) free\'d
==85414== 
==85414== 
==85414== Process terminating with default action of signal 11 (SIGSEGV)
==85414==  General Protection Fault
==85414==    at 0x10AED0: misaligned_stack_error_ (in /usr/lib/libSystem.B.dylib)
==85414==    by 0x1E45E87: -[NSCustomReleaseData dealloc] (in /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit)
==85414==    by 0x1E45E37: -[NSBitmapImageRep _freeData] (in /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit)
==85414==    by 0x1E45DCA: -[NSBitmapImageRep _freeImage] (in /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit)
==85414==    by 0x1E45D74: -[NSBitmapImageRep dealloc] (in /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit)
==85414==    by 0x171DF37: CFRelease (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==85414==    by 0x1748691: __CFArrayReleaseValues (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==85414==    by 0x171E100: _CFRelease (in /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation)
==85414==    by 0x1D89F7A: -[NSImage dealloc] (in /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit)
==85414==    by 0x20857D4: -[NSCursor dealloc] (in /System/Library/Frameworks/AppKit.framework/Versions/C/AppKit)
==85414==    by 0xDFE33: QZ_FreeWMCursor (in /opt/PalmPDK/host/lib/libSDL-1.2.0.11.2.dylib)
==85414==    by 0xCA11F: SDL_FreeCursor (in /opt/PalmPDK/host/lib/libSDL-1.2.0.11.2.dylib)
--85414:0:schedule VG_(sema_down): read returned -4
请注意，前两个条件跳转错误每次都会发生，并且可能与我的应用程序无关。仅当我尝试在OSX上使用版本1时，才会发生无效的读取错误。     

解决方法

        它可能根本与您的顶点数组无关。例如，可能仍然有指向其他顶点属性集的指针，当然，如果这些缓冲区的缓冲区小于新顶点数组的缓冲区，则会出现段错误。 如果仔细查看valgrind输出，您会发现仍然存在纹理坐标指针集。 因此，我建议您禁用所有不需要的顶点属性数组： 
glDisableClientState(GL_NORMAL_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
/* ... */
在你的情况下 
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    
gldrawarrays元素元素出现出现太多段错误绘制绘制错误错误错误

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