From 4c86ed4980d0f277dc4b9194fa9178d7881a669c Mon Sep 17 00:00:00 2001
From: William S Fulton <wsf@fultondesigns.co.uk>
Date: Tue, 1 Oct 2019 08:05:35 +0100
Subject: [PATCH] Macros wrapped as constants documentation improvements.

Closes #1618
---
 Doc/Manual/SWIG.html | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Doc/Manual/SWIG.html b/Doc/Manual/SWIG.html
index aec48ef03..c54d117e0 100644
--- a/Doc/Manual/SWIG.html
+++ b/Doc/Manual/SWIG.html
@@ -826,6 +826,32 @@ However, for the same conservative reasons even a constant with a simple cast wi
 </pre>
 </div>
 
+<p>
+This logic can lead to false attempts at converting <tt>#define</tt> into <tt>%constant</tt> though.
+For example the following case does not have any undefined symbols within the macro:
+</p>
+
+<div class="code">
+<pre>
+// For indicating pure virtual functions such as: virtual void f() PURE;
+#define PURE = 0
+</pre>
+</div>
+
+<p>
+A warning is issued:
+</p>
+
+<div class="shell">
+<pre>
+pure.h:1: Warning 305: Bad constant value (ignored).
+</pre>
+</div>
+
+<p>
+In such cases simply ignore the warning or suppress it using the normal warning suppression techniques.
+</p>
+
 <p>
 The use of constant expressions is allowed, but SWIG does not evaluate
 them. Rather, it passes them through to the output file and lets the C