mesa: handle zero-size buffers in MapBuffer and ranges in MapBufferRange (v3)

Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/bufferobj.c

@@ -1004,6 +1004,12 @@ _mesa_MapBufferARB(GLenum target, GLenum access)
       return NULL;
    }
 
+   if (!bufObj->Size) {
+      _mesa_error(ctx, GL_OUT_OF_MEMORY,
+                  "glMapBuffer(buffer size = 0)");
+      return NULL;
+   }
+
    ASSERT(ctx->Driver.MapBufferRange);
    map = ctx->Driver.MapBufferRange(ctx, 0, bufObj->Size, accessFlags, bufObj);
    if (!map) {
@@ -1411,6 +1417,22 @@ _mesa_MapBufferRange(GLenum target, GLintptr offset, GLsizeiptr length,
       return NULL;
    }
 
+   if (!bufObj->Size) {
+      _mesa_error(ctx, GL_OUT_OF_MEMORY,
+                  "glMapBufferRange(buffer size = 0)");
+      return NULL;
+   }
+
+   /* Mapping zero bytes should return a non-null pointer. */
+   if (!length) {
+      static long dummy = 0;
+      bufObj->Pointer = &dummy;
+      bufObj->Length = length;
+      bufObj->Offset = offset;
+      bufObj->AccessFlags = access;
+      return bufObj->Pointer;
+   }
+
    ASSERT(ctx->Driver.MapBufferRange);
    map = ctx->Driver.MapBufferRange(ctx, offset, length, access, bufObj);
    if (!map) {

src/mesa/state_tracker/st_cb_bufferobjects.c

@@ -228,13 +228,6 @@ st_bufferobj_data(struct gl_context *ctx,
 }
 
 
-/**
- * Dummy data whose's pointer is used for zero size buffers or ranges.
- */
-static long st_bufferobj_zero_length = 0;
-
-
-
 /**
  * Called via glMapBufferRange().
  */
@@ -280,14 +273,6 @@ st_bufferobj_map_range(struct gl_context *ctx,
    assert(offset < obj->Size);
    assert(offset + length <= obj->Size);
 
-   /*
-    * We go out of way here to hide the degenerate yet valid case of zero
-    * length range from the pipe driver.
-    */
-   if (!length) {
-      obj->Pointer = &st_bufferobj_zero_length;
-   }
-   else {
    obj->Pointer = pipe_buffer_map_range(pipe,
                                         st_obj->buffer,
                                         offset, length,
@@ -296,7 +281,6 @@ st_bufferobj_map_range(struct gl_context *ctx,
    if (obj->Pointer) {
       obj->Pointer = (ubyte *) obj->Pointer + offset;
    }
-   }
 
    if (obj->Pointer) {
       obj->Offset = offset;