--- a/doc/building.html	Thu May 23 02:36:15 2019 +0200
+++ b/doc/building.html	Wed May 22 21:50:16 2019 -0400
@@ -297,6 +297,10 @@
 </tr>
 </tbody>
 </table>
+<p>All compilers are expected to be able to compile to the C99 language standard,
+as some C99 features are used in the source code. Microsoft Visual Studio
+doesn't fully support C99 so in practice shared code is limited to using C99
+features that it does support.</p>
 <h3 id="gcc">gcc</h3>
 <p>The minimum accepted version of gcc is 4.8. Older versions will generate a warning by <code>configure</code> and are unlikely to work.</p>
 <p>The JDK is currently known to be able to compile with at least version 7.4 of gcc.</p>