glDrawArrays（）在繪製太多元素時出現段錯誤

Question

我在運行Android的手機，運行webOS的手機以及使用SDL/OpenGL的Mac上運行的C++中有一些簡單的OpenGL ES代碼。有問題的代碼只是繪製一個GL_LINE_STRIP，存儲在GLfloat的數組中。以下是我正在努力做到這一點（版本1）：

GLfloat array* = new GLfloat[2048]; 
//later... (array gets filled) 
int howMany = 1024; 
glVertexPointer(2, GL_FLOAT, 0, array); checkError(); 
glDrawArrays(GL_LINE_STRIP, 0, howMany); checkError(); 

好像它應該是相當簡單的。然而，Android和我的Mac都OpenGL驅動程序裏面，上面的代碼段錯誤（似乎運行webOS的罰款，無論出於何種原因。）這是我必須做的避免這種情況（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, GL_FLOAT, 0, 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, 0, std::min(790U, howMany-i)); checkError(); 
} 

限制一次繪製的線條數量始終避免段錯誤。數字790是通過實驗確定的;在791它在OSX上崩潰（Android可以走得更高，雖然它以前被限制在113多個版本之前......所以這個數字似乎對於每個應用版本都是一致的，但不是在不同版本或平臺之間）。

在我的應用中還有很多其他的GL內容，但它是一個大型應用程序，並且發佈所有代碼都不實用。那麼，什麼可能導致這種情況？我應該研究哪些可能性？

這裏是我的程序運行的Valgrind的輸出和OSX崩潰當我嘗試使用版本1：

==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 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 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 

注意的是，前兩個條件跳轉錯誤發生的每一次，可能不會是一個問題我的應用程序當我嘗試在OSX上使用版本1時，纔會出現無效讀取錯誤。

Answer 1

它可能根本與你的頂點數組無關。例如，可能還有指向其他頂點屬性集的指針，當然，如果這些指針的緩衝區小於新的頂點數組，則會出現段錯誤。

如果你仔細看看你的valgrind輸出，你會看到，還有一個紋理座標指針集。

所以我的建議是你禁用你並不需要所有的頂點屬性數組：

glDisableClientState(GL_NORMAL_ARRAY); 
glDisableClientState(GL_COLOR_ARRAY); 
/* ... */ 

你的情況

glDisableClientState(GL_TEXTURE_COORD_ARRAY);