From 8d314811821d48f9c3b795afe21c6b9e83f3f442 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Sun, 29 Oct 2017 20:21:36 -0500
Subject: [PATCH] Report errors for illegal pointer arithmetic operations.

These include arithmetic on pointers to incomplete types or functions, as well as subtraction of pointers to incompatible types.
---
 Expression.pas | 9 +++++++++
 Scanner.pas    | 1 +
 2 files changed, 10 insertions(+)

diff --git a/Expression.pas b/Expression.pas
index 1a11bcf..58e8de2 100644
--- a/Expression.pas
+++ b/Expression.pas
@@ -2170,6 +2170,8 @@ procedure ChangePointer (op: pcodes; size: longint; tp: baseTypeEnum);
 {    tp - type of the integer operand                           }
 
 begin {ChangePointer}
+if size = 0 then
+   Error(122);
 case tp of
    cgByte,cgUByte,cgWord,cgUWord: begin
       if (size = long(size).lsw) and (op = pc_adl)
@@ -2494,6 +2496,8 @@ var
             end {if}
          else {if iType^.kind = pointerType then} begin
             lSize := iType^.pType^.size;
+            if lSize = 0 then
+               Error(122);
             if long(lSize).msw <> 0 then begin
 
                {handle inc/dec of >64K}
@@ -3359,6 +3363,11 @@ case tree^.token.kind of
          if expressionType^.kind in [arrayType,pointerType] then begin
 
             {subtraction of two pointers}
+            if size = 0 then
+               Error(122)
+                            {NOTE: assumes aType & pType overlap in typeRecord}
+            else if not CompTypes(lType^.aType, expressionType^.aType) then
+               Error(47);
             Gen0(pc_sbl);
             if size <> 1 then begin
                GenLdcLong(size);
diff --git a/Scanner.pas b/Scanner.pas
index 7843788..86d51bb 100644
--- a/Scanner.pas
+++ b/Scanner.pas
@@ -604,6 +604,7 @@ if list or (numErr <> 0) then begin
         119: msg := @'inline specifier is only allowed on functions';
         120: msg := @'non-static inline functions are not supported';
         121: msg := @'invalid digit for binary constant';
+        122: msg := @'arithmetic is not allowed on a pointer to an incomplete or function type';
          otherwise: Error(57);
          end; {case}
        writeln(msg^);