Fixed a crash using TransformFeedback with DrawArraysInstanced

src/OpenGL/libGLESv2/Program.cpp

@@ -1261,10 +1261,14 @@ namespace es2
 			// In INTERLEAVED_ATTRIBS mode, the values of one or more output variables
 			// written by a vertex shader are written, interleaved, into the buffer object
 			// bound to the first transform feedback binding point (index = 0).
-			sw::Resource* resource = transformFeedbackBuffers[0].get()->getResource();
+			sw::Resource* resource = transformFeedbackBuffers[0].get() ?
+			                         transformFeedbackBuffers[0].get()->getResource() :
+			                         nullptr;
 			int componentStride = static_cast<int>(totalLinkedVaryingsComponents);
 			int baseOffset = transformFeedbackBuffers[0].getOffset() + (transformFeedback->vertexOffset() * componentStride * sizeof(float));
 			maxVaryings = sw::min(maxVaryings, (unsigned int)sw::MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS);
+			ASSERT(resource || (maxVaryings == 0));
+
 			int totalComponents = 0;
 			for(unsigned int index = 0; index < maxVaryings; ++index)
 			{

tests/GLESUnitTests/unittests.cpp

@@ -950,6 +950,50 @@ TEST_F(SwiftShaderTest, AtanCornerCases)
 	Uninitialize();
 }
 
+TEST_F(SwiftShaderTest, TransformFeedback_DrawArraysInstanced)
+{
+	Initialize(3, false);
+
+	const char * data0[] =
+	{
+		"#version 300 es\n"
+		"in mediump vec2 vary;"
+		"out mediump vec4 color;"
+		"void main()"
+		"{\t"
+			"color = vec4(vary, 0.0, 1.0);"
+		"}"
+	};
+	const char * data1[] =
+	{
+		"#version 300 es\n"
+		"layout(location=0) in mediump vec2 pos;"
+		"out mediump vec2 vary;"
+		"void main()"
+		"{\t"
+			"vary = pos;\t"
+			"gl_Position = vec4(pos, 0.0, 1.0);"
+		"}"
+	};
+
+	GLuint vert = glCreateShader(GL_VERTEX_SHADER);
+	GLuint frag = glCreateShader(GL_FRAGMENT_SHADER);
+	GLuint program = glCreateProgram();
+
+	glShaderSource(frag, 1, data0, (const GLint *)0);
+	glAttachShader(program, vert);
+	glCompileShader(frag);
+	glAttachShader(program, frag);
+	glShaderSource(vert, 1, data1, (const GLint *)0);
+	glCompileShader(vert);
+	glLinkProgram(program);
+	glUseProgram(program);
+	glBeginTransformFeedback(GL_POINTS);
+	glDrawArraysInstanced(GL_POINTS, 0, 1, 1);
+
+	Uninitialize();
+}
+
 // Test conditions that should result in a GL_OUT_OF_MEMORY and not crash
 TEST_F(SwiftShaderTest, OutOfMemory)
 {