[Mesa-dev] [PATCH] mesa: handle zero-size buffers in MapBuffer and ranges in MapBufferRange (v3)

[Marek Olšák]

---
 src/mesa/main/bufferobj.c                    |   24 ++++++++++++++++++-
 src/mesa/state_tracker/st_cb_bufferobjects.c |   32 ++++++-------------------
 2 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/src/mesa/main/bufferobj.c b/src/mesa/main/bufferobj.c
index c453f9c..a303401 100644
--- a/src/mesa/main/bufferobj.c
+++ b/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) {
@@ -1410,7 +1416,23 @@ _mesa_MapBufferRange(GLenum target, GLintptr offset, GLsizeiptr length,
                   "glMapBufferRange(buffer already mapped)");
       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) {
diff --git a/src/mesa/state_tracker/st_cb_bufferobjects.c b/src/mesa/state_tracker/st_cb_bufferobjects.c
index a451b44..aab7444 100644
--- a/src/mesa/state_tracker/st_cb_bufferobjects.c
+++ b/src/mesa/state_tracker/st_cb_bufferobjects.c
@@ -229,13 +229,6 @@ 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().
  */
 static void *
@@ -280,24 +273,15 @@ 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,
-                                           flags,
-                                           &st_obj->transfer);
-      if (obj->Pointer) {
-         obj->Pointer = (ubyte *) obj->Pointer + offset;
-      }
+   obj->Pointer = pipe_buffer_map_range(pipe,
+                                        st_obj->buffer,
+                                        offset, length,
+                                        flags,
+                                        &st_obj->transfer);
+   if (obj->Pointer) {
+      obj->Pointer = (ubyte *) obj->Pointer + offset;
    }
-   
+
    if (obj->Pointer) {
       obj->Offset = offset;
       obj->Length = length;
-- 
1.7.4.1