From 3417a98d1022b3abc4e6d85721282c3d4db8a246 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Tue, 14 Feb 2023 18:53:27 -0600
Subject: [PATCH] Use proper data bank when calling comparison function in
 qsort.

When using the large memory model, the wrong data bank (that of the library code rather than the program's static data) would be in place when the comparison function was called, potentially leading to data corruption or other incorrect behavior.
---
 stdlib.asm | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/stdlib.asm b/stdlib.asm
index bcbe300..329c67b 100644
--- a/stdlib.asm
+++ b/stdlib.asm
@@ -700,13 +700,14 @@ ret      stx   n
 qsort    start
 
          csubroutine (4:base,4:count,4:size,4:compar),0
-         phb
-         phk
-         plb
 
          lda   count                    nothing to do if count is 0
          ora   count+2
          beq   done
+
+         phb
+         phk
+         plb
          dec4  count                    set count to the addr of the last entry
          mul4  count,size
          add4  count,base
@@ -717,12 +718,13 @@ qsort    start
          lda   compar+1
          sta   jsl1+2
          sta   jsl2+2
+         plb
+
          ph4   <count                   do the sort
          ph4   <base
          jsl   rsort
 
-done     plb
-         creturn
+done     creturn
          end
 
 ****************************************************************
@@ -781,10 +783,14 @@ sr1a     move4 last,right               right = last
          move4 first,left               left = first
          bra   sr3
 sr2      add4  left,lsize               inc left until *left >= *last
-sr3      ph4   <last
+sr3      plb
+         ph4   <last
          ph4   <left
 jsl1     entry
          jsl   jsl1
+         phb
+         phk
+         plb
          tax
          bmi   sr2
 sr4      lda   right                    quit if right = first
@@ -794,10 +800,14 @@ sr4      lda   right                    quit if right = first
          cmp   first+2
          beq   sr4b
 sr4a     sub4  right,lsize              dec right until *right <= *last
+         plb
          ph4   <last
          ph4   <right
 jsl2     entry
          jsl   jsl2
+         phb
+         phk
+         plb
          dec   A
          bpl   sr4
 sr4b     ph4   <left                    swap left/right entries
@@ -816,9 +826,13 @@ sr5      blt   sr2
          ph4   <last
          jsr   swap
          sub4  left,lsize,right         sort left part of array
+         plb
          ph4   <right
          ph4   <first
          jsl   rsort
+         phb
+         phk
+         plb
          add4  left,lsize,first         sort right part of array
          brl   sr0
 ;