mesa: fix glGetInteger*(GL_SAMPLER_BINDING).

If the sampler object has been deleted on another context, an
alternative context may reference the old sampler. So ensure the sampler
object still exists.

Note: this is a candidate for the stable branch.

Signed-off-by: Alan Hourihane <[email protected]>
Reviewed-by: Brian Paul <[email protected]>
(cherry picked from commit 5984a911f9dda3f7421bdec604d30d0dfe2cea5e)

3 files changed, 14 insertions, 2 deletions

diff --git a/src/mesa/main/get.c b/src/mesa/main/get.c
index 5f4e2fa512f..6fb2f5d5924 100644
--- a/src/mesa/main/get.c
+++ b/src/mesa/main/get.c
@@ -34,6 +34,7 @@
 #include "state.h"
 #include "texcompress.h"
 #include "framebuffer.h"
+#include "samplerobj.h"
 
 /* This is a table driven implemetation of the glGet*v() functions.
  * The basic idea is that most getters just look up an int somewhere
@@ -823,7 +824,16 @@ find_custom_value(struct gl_context *ctx, const struct value_desc *d, union valu
       {
          struct gl_sampler_object *samp =
             ctx->Texture.Unit[ctx->Texture.CurrentUnit].Sampler;
-         v->value_int = samp ? samp->Name : 0;
+
+         /*
+          * The sampler object may have been deleted on another context,
+          * so we try to lookup the sampler object before returning its Name.
+          */
+         if (samp && _mesa_lookup_samplerobj(ctx, samp->Name)) {
+            v->value_int = samp->Name;
+         } else {
+            v->value_int = 0;
+         }
       }
       break;
    /* GL_ARB_uniform_buffer_object */
diff --git a/src/mesa/main/samplerobj.c b/src/mesa/main/samplerobj.c
index 4664cc34053..5cff329367b 100644
--- a/src/mesa/main/samplerobj.c
+++ b/src/mesa/main/samplerobj.c
@@ -40,7 +40,7 @@
 #include "main/samplerobj.h"
 
 
-static struct gl_sampler_object *
+struct gl_sampler_object *
 _mesa_lookup_samplerobj(struct gl_context *ctx, GLuint name)
 {
    if (name == 0)
diff --git a/src/mesa/main/samplerobj.h b/src/mesa/main/samplerobj.h
index 311425701d0..69e389949d8 100644
--- a/src/mesa/main/samplerobj.h
+++ b/src/mesa/main/samplerobj.h
@@ -62,6 +62,8 @@ _mesa_reference_sampler_object(struct gl_context *ctx,
       _mesa_reference_sampler_object_(ctx, ptr, samp);
 }
 
+extern struct gl_sampler_object *
+_mesa_lookup_samplerobj(struct gl_context *ctx, GLuint name);
 
 extern struct gl_sampler_object *
 _mesa_new_sampler_object(struct gl_context *ctx, GLuint name);