From 78de47ca24044039cf3b760ef22e7fa184df45df Mon Sep 17 00:00:00 2001
From: Sergey Sharybin <sergey.vfx@gmail.com>
Date: Wed, 1 Jul 2015 11:56:48 +0200
Subject: [PATCH] Cycles: Fix zero-size buffer allocation with OpenCL devices

This is not really supported by OpenCL but might happen in certain
configurations. There might be some remained cases when this happens
but so far can not find any,
---
 intern/cycles/device/device_opencl.cpp | 50 ++++++++++++++++++++------
 1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/intern/cycles/device/device_opencl.cpp b/intern/cycles/device/device_opencl.cpp
index 7ab2b412f0d..4dd92c3337a 100644
--- a/intern/cycles/device/device_opencl.cpp
+++ b/intern/cycles/device/device_opencl.cpp
@@ -941,9 +941,22 @@ public:
 		else
 			mem_flag = CL_MEM_READ_WRITE;
 
-		mem.device_pointer = (device_ptr)clCreateBuffer(cxContext, mem_flag, size, mem_ptr, &ciErr);
-
-		opencl_assert_err(ciErr, "clCreateBuffer");
+		/* Zero-size allocation might be invoked by render, but not really
+		 * supported by OpenCL. Using NULL as device pointer also doesn't really
+		 * work for some reason, so for the time being we'll use special case
+		 * will null_mem buffer.
+		 */
+		if(size != 0) {
+			mem.device_pointer = (device_ptr)clCreateBuffer(cxContext,
+			                                                mem_flag,
+			                                                size,
+			                                                mem_ptr,
+			                                                &ciErr);
+			opencl_assert_err(ciErr, "clCreateBuffer");
+		}
+		else {
+			mem.device_pointer = null_mem;
+		}
 
 		stats.mem_alloc(size);
 		mem.device_size = size;
@@ -953,15 +966,31 @@ public:
 	{
 		/* this is blocking */
 		size_t size = mem.memory_size();
-		opencl_assert(clEnqueueWriteBuffer(cqCommandQueue, CL_MEM_PTR(mem.device_pointer), CL_TRUE, 0, size, (void*)mem.data_pointer, 0, NULL, NULL));
+		if(size != 0){
+			opencl_assert(clEnqueueWriteBuffer(cqCommandQueue,
+			                                   CL_MEM_PTR(mem.device_pointer),
+			                                   CL_TRUE,
+			                                   0,
+			                                   size,
+			                                   (void*)mem.data_pointer,
+			                                   0,
+			                                   NULL, NULL));
+		}
 	}
 
 	void mem_copy_from(device_memory& mem, int y, int w, int h, int elem)
 	{
 		size_t offset = elem*y*w;
 		size_t size = elem*w*h;
-
-		opencl_assert(clEnqueueReadBuffer(cqCommandQueue, CL_MEM_PTR(mem.device_pointer), CL_TRUE, offset, size, (uchar*)mem.data_pointer + offset, 0, NULL, NULL));
+		assert(size != 0);
+		opencl_assert(clEnqueueReadBuffer(cqCommandQueue,
+		                                  CL_MEM_PTR(mem.device_pointer),
+		                                  CL_TRUE,
+		                                  offset,
+		                                  size,
+		                                  (uchar*)mem.data_pointer + offset,
+		                                  0,
+		                                  NULL, NULL));
 	}
 
 	void mem_zero(device_memory& mem)
@@ -975,7 +1004,9 @@ public:
 	void mem_free(device_memory& mem)
 	{
 		if(mem.device_pointer) {
-			opencl_assert(clReleaseMemObject(CL_MEM_PTR(mem.device_pointer)));
+			if(mem.device_pointer != null_mem) {
+				opencl_assert(clReleaseMemObject(CL_MEM_PTR(mem.device_pointer)));
+			}
 			mem.device_pointer = 0;
 
 			stats.mem_free(mem.device_size);
@@ -3325,10 +3356,9 @@ protected:
 	cl_mem mem_alloc(size_t bufsize, cl_mem_flags mem_flag = CL_MEM_READ_WRITE)
 	{
 		cl_mem ptr;
+		assert(bufsize != 0);
 		ptr = clCreateBuffer(cxContext, mem_flag, bufsize, NULL, &ciErr);
-		if(opencl_error(ciErr)) {
-			assert(0);
-		}
+		opencl_assert_err(ciErr, "clCreateBuffer");
 		return ptr;
 	}
 };