gallium: fix reference counting functions to be strict-aliasing compliant

Historically, parts of mesa code are not strict-aliasing safe, hence
-fno-strict-aliasing is needed to compile (this got forgotten for scons
builds for gallium, which indeed not only caused compiler warnings but also
unexplicable crashes in non-debug builds). However, we should try to eliminate
code not complying with strict-aliasing code at least for gallium.
Hence change pipe_reference functions to make them strict-aliasing compliant.
This adds a bit more complexity (especially for derived classes) but is the
right thing to do, and it does in fact fix a segfault.

3 files changed, 16 insertions, 14 deletions

diff --git a/src/gallium/include/pipe/p_refcnt.h b/src/gallium/include/pipe/p_refcnt.h
index 1f9088b3e9c..f1875b6b822 100644
--- a/src/gallium/include/pipe/p_refcnt.h
+++ b/src/gallium/include/pipe/p_refcnt.h
@@ -59,30 +59,28 @@ pipe_is_referenced(struct pipe_reference *reference)
 
 
 /**
- * Set 'ptr' to point to 'reference' and update reference counting.
- * The old thing pointed to, if any, will be unreferenced first.
- * 'reference' may be NULL.
+ * Update reference counting.
+ * The old thing pointed to, if any, will be unreferenced.
+ * Both 'ptr' and 'reference' may be NULL.
  */
 static INLINE bool
-pipe_reference(struct pipe_reference **ptr, struct pipe_reference *reference)
+pipe_reference(struct pipe_reference *ptr, struct pipe_reference *reference)
 {
    bool destroy = FALSE;
 
-   if(*ptr != reference) {
+   if(ptr != reference) {
       /* bump the reference.count first */
       if (reference) {
          assert(pipe_is_referenced(reference));
          p_atomic_inc(&reference->count);
       }
    
-      if (*ptr) {
-         assert(pipe_is_referenced(*ptr));
-         if (p_atomic_dec_zero(&(*ptr)->count)) {
+      if (ptr) {
+         assert(pipe_is_referenced(ptr));
+         if (p_atomic_dec_zero(&ptr->count)) {
             destroy = TRUE;
          }
       }
-   
-      *ptr = reference;
    }
 
    return destroy;
diff --git a/src/gallium/include/pipe/p_state.h b/src/gallium/include/pipe/p_state.h
index 6de7af6a81c..b9dfa1c7d3c 100644
--- a/src/gallium/include/pipe/p_state.h
+++ b/src/gallium/include/pipe/p_state.h
@@ -400,8 +400,9 @@ pipe_buffer_reference(struct pipe_buffer **ptr, struct pipe_buffer *buf)
 {
    struct pipe_buffer *old_buf = *ptr;
 
-   if (pipe_reference((struct pipe_reference **)ptr, &buf->reference))
+   if (pipe_reference(&(*ptr)->reference, &buf->reference))
       old_buf->screen->buffer_destroy(old_buf);
+   *ptr = buf;
 }
 
 static INLINE void
@@ -409,8 +410,9 @@ pipe_surface_reference(struct pipe_surface **ptr, struct pipe_surface *surf)
 {
    struct pipe_surface *old_surf = *ptr;
 
-   if (pipe_reference((struct pipe_reference **)ptr, &surf->reference))
+   if (pipe_reference(&(*ptr)->reference, &surf->reference))
       old_surf->texture->screen->tex_surface_destroy(old_surf);
+   *ptr = surf;
 }
 
 static INLINE void
@@ -418,8 +420,9 @@ pipe_texture_reference(struct pipe_texture **ptr, struct pipe_texture *tex)
 {
    struct pipe_texture *old_tex = *ptr;
 
-   if (pipe_reference((struct pipe_reference **)ptr, &tex->reference))
+   if (pipe_reference(&(*ptr)->reference, &tex->reference))
       old_tex->screen->texture_destroy(old_tex);
+   *ptr = tex;
 }
 
 
diff --git a/src/gallium/include/pipe/p_video_state.h b/src/gallium/include/pipe/p_video_state.h
index 4da26d608cf..b85f01c2b02 100644
--- a/src/gallium/include/pipe/p_video_state.h
+++ b/src/gallium/include/pipe/p_video_state.h
@@ -56,8 +56,9 @@ pipe_video_surface_reference(struct pipe_video_surface **ptr, struct pipe_video_
 {
    struct pipe_video_surface *old_surf = *ptr;
 
-   if (pipe_reference((struct pipe_reference **)ptr, &surf->reference))
+   if (pipe_reference(&(*ptr)->reference, &surf->reference))
       old_surf->screen->video_surface_destroy(old_surf);
+   *ptr = surf;
 }
 
 struct pipe_video_rect