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On 08/30/2011 10:15 AM, Marek Olšák wrote:
> Moved from st/mesa.
> This also fixes an assertion failure in piglit/fdo31934 on gallium drivers.
So... I guess I don't understand why the mapping can't just fail and set
GL_OUT_OF_MEMORY. Returning a pointer to some random bit of storage
seems like a recipe for bugs that are excruciating for app developers to
debug.
I'd be more inclined to return an invalid pointer, like (void
*)0xdeadbeef, so the reads or writes through it will cause the segfault
that the app deserves.
> ---
> src/mesa/main/bufferobj.c | 18 +++++++++++++-
> src/mesa/state_tracker/st_cb_bufferobjects.c | 32 ++++++-------------------
> 2 files changed, 25 insertions(+), 25 deletions(-)
>
> diff --git a/src/mesa/main/bufferobj.c b/src/mesa/main/bufferobj.c
> index c453f9c..515abc5 100644
> --- a/src/mesa/main/bufferobj.c
> +++ b/src/mesa/main/bufferobj.c
> @@ -1004,6 +1004,13 @@ _mesa_MapBufferARB(GLenum target, GLenum access)
> return NULL;
> }
>
> + /* Handle zero-size buffers here rather than in drivers. */
> + if (!bufObj->Size) {
> + /* Dummy data whose pointer is used for zero-size buffers. */
> + static long bufferobj_zero_length = 0;
> + return &bufferobj_zero_length;
> + }
> +
> ASSERT(ctx->Driver.MapBufferRange);
> map = ctx->Driver.MapBufferRange(ctx, 0, bufObj->Size, accessFlags,
> bufObj);
> if (!map) {
> @@ -1410,7 +1417,16 @@ _mesa_MapBufferRange(GLenum target, GLintptr offset,
> GLsizeiptr length,
> "glMapBufferRange(buffer already mapped)");
> return NULL;
> }
> -
> +
> + /* We go out of way here to hide the degenerate yet valid case of zero
> + * length range.
> + */
> + if (!length) {
> + /* Dummy data whose pointer is used for zero-size buffers. */
> + static long bufferobj_zero_length = 0;
> + return &bufferobj_zero_length;
> + }
> +
> 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;
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