[Mesa-dev] [PATCH] glx: Be slightly more tolerant in glXImportContext

[Adam Jackson]

Ugh the GLX code. __GLX_MAX_CONTEXT_PROPS is 3 because glxproto.h is
just a pile of ancient runes, so when the server begins sending more
than 3 context properties this code refuses to work _at all_.

This extension is pretty obscure, so this probably isn't a big deal (if
it was we'd need to hack the server side to send fewer properties unless
the client seemed to be "new enough"). And we're probably not going to
ever have tremendous numbers of context properties. So bump the number
we'll accept in a reply out to 32 (since we still want to avoid overflow
etc.) and copy in just the ones we know about, as since these will be
indirect contexts the client library probably needs to be explicitly
aware of any new context state.

Signed-off-by: Adam Jackson <ajax at redhat.com>
---
 src/glx/glxcmds.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/glx/glxcmds.c b/src/glx/glxcmds.c
index 29b94b8810..fd917671eb 100644
--- a/src/glx/glxcmds.c
+++ b/src/glx/glxcmds.c
@@ -1395,6 +1395,16 @@ GLX_ALIAS(Display *, glXGetCurrentDisplayEXT, (void), (),
           glXGetCurrentDisplay)
 
 #ifndef GLX_USE_APPLEGL
+
+/*
+ * This is just a random large number, so that the server can start sending
+ * more properties and we won't arbitrarily reject it, but we still won't save
+ * any attributes we don't know about, since the correct usage of an imported
+ * (and thus indirect) context almost certainly requires explicit awareness in
+ * libGL of any extensions in use. Right now we know about 5, 32 should be
+ * plenty of headroom.
+ */
+#define MAX_CONTEXT_PROPS 32
 _GLX_PUBLIC GLXContext
 glXImportContextEXT(Display *dpy, GLXContextID contextID)
 {
@@ -1403,11 +1413,7 @@ glXImportContextEXT(Display *dpy, GLXContextID contextID)
    xGLXQueryContextReply reply;
    CARD8 opcode;
    struct glx_context *ctx;
-
-   /* This GLX implementation knows about 5 different properties, so
-    * allow the server to send us one of each.
-    */
-   int propList[5 * 2], *pProp, nPropListBytes;
+   int propList[MAX_CONTEXT_PROPS * 2], *pProp, nPropListBytes;
    int numProps;
    int i, renderType;
    XID share;
@@ -1471,7 +1477,7 @@ glXImportContextEXT(Display *dpy, GLXContextID contextID)
 
    _XReply(dpy, (xReply *) & reply, 0, False);
 
-   if (reply.n <= __GLX_MAX_CONTEXT_PROPS)
+   if (reply.n <= MAX_CONTEXT_PROPS)
       nPropListBytes = reply.n * 2 * sizeof propList[0];
    else
       nPropListBytes = 0;
-- 
2.14.1