Mesa (master): mesa: Don't error on glFeedbackBuffer(size = 0, buffer = NULL)

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 07e5295b6fe77253ea38dbc0d649b20e7275373a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=07e5295b6fe77253ea38dbc0d649b20e7275373a

Author: Eric Anholt <eric at anholt.net>
Date:   Tue Jun 28 16:39:15 2011 -0700

mesa: Don't error on glFeedbackBuffer(size = 0, buffer = NULL)

The existing error result doesn't appear in the GL 2.1 or 3.2
compatibility specs, and triggers an unexpected GL error in Intel's
oglconform when it tries to reset the feedback state after usage so
that the "diff the state at error time vs. context init time" code
doesn't generate spurious diffs.  The unexpected GL error then
translates into testcase failure.  Brian wants the safety check on
buffer = NULL, though, so that people can't as easily set up a broken
buffer.

---

 src/mesa/main/feedback.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/mesa/main/feedback.c b/src/mesa/main/feedback.c
index fcb089f..597ec1e 100644
--- a/src/mesa/main/feedback.c
+++ b/src/mesa/main/feedback.c
@@ -64,7 +64,7 @@ _mesa_FeedbackBuffer( GLsizei size, GLenum type, GLfloat *buffer )
       _mesa_error( ctx, GL_INVALID_VALUE, "glFeedbackBuffer(size<0)" );
       return;
    }
-   if (!buffer) {
+   if (!buffer && size > 0) {
       _mesa_error( ctx, GL_INVALID_VALUE, "glFeedbackBuffer(buffer==NULL)" );
       ctx->Feedback.BufferSize = 0;
       return;