Bug 101464

Summary:	PrimitiveRestartNV inside a render list causes a crash
Product:	Mesa	Reporter:	Olivier Lauffenburger <o.lauffenburger>
Component:	Mesa core	Assignee:	mesa-dev
Status:	RESOLVED FIXED	QA Contact:	mesa-dev
Severity:	major
Priority:	medium
Version:	17.0
Hardware:	x86-64 (AMD64)
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description Olivier Lauffenburger 2017-06-16 08:50:54 UTC

When using glDrawElements with glPrimitiveRestartIndexNV during the compilation of a render list, there is a crash when Mesa reaches the second restart index of the array.

The reason is that when PrimitiveRestartNV is called internally the first time, save_PrimitiveRestartNV() (in \src\mesa\vbo\vbo_save_api.c) is called. It executes _save_End() and _save_Begin(curPrim), but _save_Begin() is a noop function that merely raises an OpenGL error "Recursive glBegin".

Comment 1 Olivier Lauffenburger 2017-06-21 08:45:09 UTC

I have replaced the content of save_PrimitiveRestartNV() by the following code to make it work:

static void GLAPIENTRY
_save_PrimitiveRestartNV(void)
{
   GLenum curPrim;
   GET_CURRENT_CONTEXT(ctx);

   /* get current primitive mode */
   struct vbo_save_context *save = &vbo_context(ctx)->save;
   if (save->prim_count == 0) return;

   const GLuint i = save->prim_count - 1;

   curPrim = save->prim[i].mode;

   /* restart primitive */
   CALL_End(GET_DISPATCH(), ());
   vbo_save_NotifyBegin(ctx, (curPrim | VBO_SAVE_PRIM_WEAK
	   | VBO_SAVE_PRIM_NO_CURRENT_UPDATE));
}

Contrarily to what is stated, ctx->Driver.CurrentSavePrimitive is not correctly set before _save_PrimitiveRestartNV() is called, whence this intricate code to get the current primitive mode...

Comment 2 Brian Paul 2017-07-07 19:01:36 UTC

I've committed a patch based on your suggestion (commit f5c8bb1e00f358e05ed21f8ed69c9fc3803bf95f) plus an patch for another failure case (commit 9ac55e8219e1f6abeab3c779c8fe710c2bc25f2b).
Closing this bug.

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