[C2y] Add C2y documents to the tracking page

These documents were adopted in the past two meetings; the current
working draft doesn't yet incorporate them however.

Author: AaronBallman

clang/www/c_status.html

@@ -69,6 +69,11 @@ <h1>C Support in Clang</h1>
  <td><tt>-std=c23</tt></td>
  <td class="partial" align="center">Partial</td>
 </tr>
+<tr>
+ <td><a href="#c2y">C2y</a></td>
+ <td><tt>(Flag currently unavailable)</tt></td>
+ <td class="partial" align="center">Partial</td>
+</tr>
 </table>
 
 <p>The implementation status for C11 and C23 are currently under investigation.
@@ -81,7 +86,7 @@ <h1>C Support in Clang</h1>
 they become available.</p>
 
 <p>The <a href="https://github.com/llvm/llvm-project/issues/">LLVM bug tracker</a> uses
-the "c", "c99", "c11", "c17", and "c23" labels to track known bugs with Clang's language
+the "c", "c99", "c11", "c17", "c23", and "c2y" labels to track known bugs with Clang's language
 conformance.</p>
 
 <h2 id="c89">C89 implementation status</h2>
@@ -1220,6 +1225,79 @@ <h2 id="c2x">C23 implementation status</h2>
 </table>
 </details>
 
+<h2 id="c2y">C2y implementation status</h2>
+
+<p>Clang has support for some of the features of the C standard following C23, informally referred to as C2y.</p>
+
+<p>Clang currently does not expose a language standard mode flag for C2y.
+<!--You can use Clang in C2y mode with the <code>-std=c2y</code> option (available in Clang 19 and later).--></p>
+
+<details open>
+<summary>List of features and minimum Clang version with support</summary>
+
+<table width="689" border="1" cellspacing="0">
+ <tr>
+    <th>Language Feature</th>
+    <th>C2y Proposal</th>
+    <th>Available in Clang?</th>
+ </tr>
+    <!-- Strasbourg 2024 Papers -->
+    <tr>
+      <td>Sequential hexdigits</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3192.pdf">N3192</a></td>
+      <td class="full" align="center">Yes</td>
+    </tr>
+    <!-- Jun 2024 Papers -->
+    <tr>
+      <td>Generic selection expression with a type operand</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3260.pdf">N3260</a></td>
+      <td class="full" align="center">Clang 17</td>
+    </tr>
+    <tr>
+      <td>Round-trip rounding</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3232.pdf">N3232</a></td>
+      <td class="unknown" align="center">Unknown</td>
+    </tr>
+    <tr>
+      <td>Accessing byte arrays</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3254.pdf">N3254</a></td>
+      <td class="unknown" align="center">Unknown</td>
+    </tr>
+    <tr>
+      <td>Slay some earthly demons I</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3244.pdf">N3244</a></td>
+      <td class="unknown" align="center">Unknown</td>
+      <!-- Voted in:
+             Annex J Item 21 (including additional change)
+             Annex J Item 56
+             Annex J Item 57 Option 1
+             Annex J Item 67
+             Annex J Item 69 (alternative wording for semantics)
+      -->
+    </tr>
+    <tr>
+      <td>Support ++ and -- on complex values</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3259.pdf">N3259</a></td>
+      <td class="full" align="center">Yes</td>
+    </tr>
+    <tr>
+      <td>Usability of a byte-wise copy of va_list</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3262.pdf">N3262</a></td>
+      <td class="unknown" align="center">Unknown</td>
+    </tr>
+    <tr>
+      <td>alignof of an incomplete array type</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3273.pdf">N3273</a></td>
+      <td class="full" align="center">Clang 3.5</td>
+    </tr>
+    <tr>
+      <td>Remove imaginary types</td>
+      <td><a href="https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3274.pdf">N3274</a></td>
+      <td class="unknown" align="center">Unknown</td>
+    </tr>
+</table>
+</details>
+
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