From 944caf84ede14c9915c657dcfb61f1fbc1ff0cdb Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Sun, 10 Jan 2016 13:51:04 +0000
Subject: [PATCH] src/: Write `NULL' for a null pointer, rather than plain `0'.

This isn't my usual style, but others may like it more.  The output is
controlled by a new variable `*null-pointer*'.  Maybe it will be
configurable later.
---
 doc/SYMBOLS            | 1 +
 doc/clang.tex          | 3 ++-
 src/codegen-proto.lisp | 3 +++
 src/method-impl.lisp   | 2 +-
 src/method-proto.lisp  | 2 +-
 5 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/doc/SYMBOLS b/doc/SYMBOLS
index 5ee51b3..bb6b944 100644
--- a/doc/SYMBOLS
+++ b/doc/SYMBOLS
@@ -326,6 +326,7 @@ codegen-impl.lisp
   temporary-variable                            class
 
 codegen-proto.lisp
+  *null-pointer*                                variable
   *sod-ap*                                      variable
   *sod-master-ap*                               variable
   block-inst                                    class
diff --git a/doc/clang.tex b/doc/clang.tex
index f5b16a8..9da2f36 100644
--- a/doc/clang.tex
+++ b/doc/clang.tex
@@ -859,7 +859,8 @@ Temporary names are represented by objects which implement a simple protocol.
   \begin{tabular}[C]{*2{>{\codeface}l}}                            \hlx*{hv}
     \thd{\textbf{Variable}} & \thd{\textbf{Name format}}        \\ \hlx{vhv}
     {}*sod-ap*                  & sod__ap                       \\
-    {}*sod-master-ap*           & sod__master_ap                \\ \hlx*{vh}
+    {}*sod-master-ap*           & sod__master_ap                \\
+    {}*null-pointer*            & NULL                          \\ \hlx*{vh}
   \end{tabular}
   \caption{Well-known temporary names}
   \label{tab:codegen.codegen.well-known-temps}
diff --git a/src/codegen-proto.lisp b/src/codegen-proto.lisp
index 4bfaeca..c115671 100644
--- a/src/codegen-proto.lisp
+++ b/src/codegen-proto.lisp
@@ -67,6 +67,9 @@
 (defparameter *sod-tmp-val*
   (make-instance 'temporary-name :tag "sod__t"))
 
+(export '*null-pointer*)
+(defparameter *null-pointer* "NULL")
+
 ;;;--------------------------------------------------------------------------
 ;;; Instructions.
 
diff --git a/src/method-impl.lisp b/src/method-impl.lisp
index 8501a02..e4aaae3 100644
--- a/src/method-impl.lisp
+++ b/src/method-impl.lisp
@@ -337,7 +337,7 @@
 		(sod-class-nickname message-class)
 		(sod-message-name message)
 		(sod-class-nickname chain-head))
-	0)))
+	*null-pointer*)))
 
 (defmethod method-entry-slot-name ((entry method-entry))
   (let* ((method (method-entry-effective-method entry))
diff --git a/src/method-proto.lisp b/src/method-proto.lisp
index 069f7e4..36237d6 100644
--- a/src/method-proto.lisp
+++ b/src/method-proto.lisp
@@ -407,7 +407,7 @@
 		   (make-trampoline codegen (sod-method-class method)
 				    (lambda (target)
 				      (invoke chain target)))
-		   0))
+		   *null-pointer*))
 	     (invoke (chain target)
 	       (if (null chain)
 		   (funcall kernel target)
-- 
2.11.0