[PATCH v3 0/1] MR9375: opengl32: Avoid null pointer dereferences when filtering extensions.

[Tim Clem (＠tclem)]

Fixes: 2127e9ae7d90466f3b8883708799047214409832

---

Fixes a crash on macOS. Perhaps the extensions string regularly has a trailing space on other platforms?
The previous filter_extensions_list method set `end` differently and avoided this case.

--
  v3: opengl32: Avoid null pointer dereferences when filtering extensions.
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/9375

[PATCH v3 1/1] opengl32: Avoid null pointer dereferences when filtering extensions.

[Tim Clem]

From: Tim Clem <tclem(a)codeweavers.com>

Fixes: 2127e9ae7d90466f3b8883708799047214409832
---
 dlls/opengl32/unix_wgl.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/dlls/opengl32/unix_wgl.c b/dlls/opengl32/unix_wgl.c
index b7892c2851d..5a86e40b1f5 100644
--- a/dlls/opengl32/unix_wgl.c
+++ b/dlls/opengl32/unix_wgl.c
@@ -742,13 +742,15 @@ static GLubyte *filter_extensions( struct context *ctx, const char *extensions )
     {
         while (*extensions == ' ') extensions++;
         if (!*extensions) break;
-        len = (end = strchr( extensions, ' ' )) ? end - extensions : strlen( extensions );
-        memcpy( p, extensions, len );
-        p[len] = 0;
+
+        if (!(end = strchr( extensions, ' ' ))) end = extensions + strlen( extensions );
+        memcpy( p, extensions, end - extensions );
+        p[end - extensions] = 0;
+
         if (is_extension_supported( ctx, p ))
         {
             TRACE( "++ %s\n", p );
-            p += len;
+            p += end - extensions;
             *p++ = ' ';
         }
         else
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/9375

[Tim Clem (＠tclem)]

On Wed Nov  5 18:47:58 2025 +0000, Rémi Bernon wrote:
> ```suggestion:-19+0
>     for (;;)
>     {
>         while (*extensions == ' ') extensions++;
>         if (!*extensions) break;
>         if (!(end = strchr( extensions, ' ' ))) end = extensions +
> strlen( extensions );
>         memcpy( p, extensions, end - extensions );
>         p[end - extensions] = 0;
>         if (is_extension_supported( ctx, p ))
>         {
>             TRACE( "++ %s
> ", p );
>             p += end - extensions;
>             *p++ = ' ';
>         }
>         else
>         {
>             TRACE( "-- %s (disabled in context)\n", p );
>         }
>         extensions = end;
>     }
> ```
> Lets take the original code which didn't suffer from the issue. The
> combined assignation and ternary operator is ugly and we can get rid of
> the len variable.

Switched back to that in v3

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/9375#note_120908