From 6d8e019443e1ce1a7d33522937bb1446b3ada709 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Sun, 28 Nov 2021 14:28:42 -0600
Subject: [PATCH] Work around SANE bug in FX2C.

This could give incorrect results for extended-to-comp conversions of certain negative integers like -2147483648 and -53021371269120. To get a fix for the same problem with regard to long long, ORCA/C should be linked with the latest version of ORCALib (which also works around some instances of the problem at run time). There are still other cases involving code in SysFloat that has not yet been patched.
---
 CGC.asm  | 35 ++++++++++++++++++++++++++++++++++-
 cc.notes |  2 ++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/CGC.asm b/CGC.asm
index 6720205..a70587e 100644
--- a/CGC.asm
+++ b/CGC.asm
@@ -40,6 +40,9 @@ rec_ext  equ   10                       disp to extended (SANE) value
 *  Inputs:
 *        rec - pointer to a record
 *
+*  Note: This avoids calling FX2C on negative numbers,
+*  because it is buggy for certain values.
+*
 ****************************************************************
 *
 CnvSC    start cg
@@ -51,6 +54,11 @@ rec_cmp  equ   20                       disp to comp (SANE) value
          tsc                            set up DP
          phd
          tcd
+         ldy   #rec_real+8
+         lda   [rec],y
+         pha                            save sign of real number
+         and   #$7fff
+         sta   [rec],y                  set sign of real number to positive
          ph4   rec                      push addr of real number
          clc                            push addr of SANE comp number
          lda   rec
@@ -61,7 +69,32 @@ rec_cmp  equ   20                       disp to comp (SANE) value
          pha
          phx
          fx2c                           convert TOS to SANE comp number
-         move4 0,4                      return
+         pla
+         bpl   ret                      if real number was negative
+         ldy   #rec_real+8                restore original sign of real number
+         sta   [rec],y
+         sec                              negate the comp value
+         ldy   #rec_cmp
+         ldx   #0
+         txa
+         sbc   [rec],y
+         sta   [rec],y
+         iny
+         iny
+         txa
+         sbc   [rec],y
+         sta   [rec],y
+         iny
+         iny
+         txa
+         sbc   [rec],y
+         sta   [rec],y
+         iny
+         iny
+         txa
+         sbc   [rec],y
+         sta   [rec],y
+ret      move4 0,4                      return
          pld
          pla
          pla
diff --git a/cc.notes b/cc.notes
index 3d74c31..645b876 100644
--- a/cc.notes
+++ b/cc.notes
@@ -1575,6 +1575,8 @@ int foo(int[42]);
 
 171. Function parameters declared with array types are adjusted to actually have pointer types, but this adjustment was not applied in some situations.  Now such parameters are consistently treated as actually having pointer types.  This affects their size as given by sizeof and their type as shown in debuggers.
 
+172. When certain negative integers that are multiples of 65536 were converted from floating-point types to long, long long, or comp, an incorrect value might be produced due to a bug in SANE.  ORCA/C now includes workarounds to avoid this bug in several situations, although it might still occur in certain other ones.
+
 -- Bugs from C 2.1.0 that have been fixed -----------------------------------
 
 1.  In some situations, fread() reread the first 1K or so of the file.