From 9c4a4110967f8bc36cb8806a4aac63562082d8fe Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Thu, 17 Sep 2015 18:24:26 +0100
Subject: [PATCH] lib/sod-structs.3: Some clarifications and typesetting fixes.

---
 lib/sod-structs.3 | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/lib/sod-structs.3 b/lib/sod-structs.3
index 6aefc9d..bc181ee 100644
--- a/lib/sod-structs.3
+++ b/lib/sod-structs.3
@@ -192,11 +192,13 @@ has no direct superclasses,
 and
 .B SodClass
 is its own metaclass.
-It is not possible to define root classes because of circularities:
+It is not possible to define root classes in module files
+because of circularities:
 .B SodObject
 has
 .B SodClass
-as its metaclass, and
+as its metaclass,
+and
 .B SodClass
 is a subclass of
 .BR SodObject .
@@ -546,7 +548,8 @@ and this is followed by corresponding members
 .IB a ;
 .PP
 for each of
-.IR C 's superclasses
+.IR C 's
+superclasses
 .IR A
 in the same chain in some (unimportant) order.
 A `pointer to
@@ -617,13 +620,17 @@ each
 .B ichain
 must have as a prefix the
 .B ichain
-for each superclass in the same chain, and
-each slot must be stored in exactly one place.
+for each superclass in the same chain,
+and each slot must be stored in exactly one place.
 The layout of vtables doesn't have this second requirement:
 it doesn't matter that there are
 multiple method entry pointers
 for the same effective method
 as long as they all work correctly.
+Indeed, it's essential that they do,
+because each chain's method entry function
+will need to apply a different offset to the receiver pointer
+before invoking the effective method.
 .PP
 A vtable for a class
 .I C
@@ -655,10 +662,8 @@ extern const union \fIC\fB__vtu_\fIh\fB \fIC\fB__vtable_\fIh\fB;
 .fi
 .PP
 The outer layer is a
-.IP
 .B union
 .IB C __vtu_ h
-.PP
 containing a member
 .IP
 .B struct
@@ -718,7 +723,7 @@ of
 The metaclass
 .I R
 of
-.IR O .
+.I O
 is then the
 .I root metaclass
 of
@@ -781,7 +786,7 @@ be the most specific superclass of
 in the same chain as
 .IR J .
 Then, if there is currently no class pointer of type
-.I Q
+.IR Q ,
 then add a member
 .RS
 .IP
@@ -825,7 +830,7 @@ If class
 .I A
 defines any messages,
 and there is currently no member
-.I a
+.IR a ,
 then add a member
 .RS
 .IP
-- 
2.11.0