From 5daa420aed60c445a444a8f7c37ab325ede1dd0c Mon Sep 17 00:00:00 2001
From: David Anderson <dvander@alliedmods.net>
Date: Sun, 20 Jul 2014 11:18:38 -0700
Subject: [PATCH] Fix inc/dec operations on accessors.

---
 sourcepawn/compiler/sc.h  |  1 +
 sourcepawn/compiler/sc3.c | 27 ++++++++++++++++++++-------
 sourcepawn/compiler/sc4.c |  6 ++++++
 3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/sourcepawn/compiler/sc.h b/sourcepawn/compiler/sc.h
index 3b81465c..7e4d5bd1 100644
--- a/sourcepawn/compiler/sc.h
+++ b/sourcepawn/compiler/sc.h
@@ -718,6 +718,7 @@ SC_FUNC void pushval(cell val);
 SC_FUNC void popreg(regid reg);
 SC_FUNC void genarray(int dims, int _autozero);
 SC_FUNC void swap1(void);
+SC_FUNC void xchg(void);
 SC_FUNC void ffswitch(int label);
 SC_FUNC void ffcase(cell value,char *labelname,int newtable);
 SC_FUNC void ffcall(symbol *sym,const char *label,int numargs);
diff --git a/sourcepawn/compiler/sc3.c b/sourcepawn/compiler/sc3.c
index 4e6e31f9..0816fa2a 100644
--- a/sourcepawn/compiler/sc3.c
+++ b/sourcepawn/compiler/sc3.c
@@ -218,7 +218,8 @@ static void (*unopers[])(void) = { lneg, neg, user_inc, user_dec };
     assert(lval!=NULL);
     if (lval->ident==iARRAYCELL || lval->ident==iARRAYCHAR)
       pushreg(sPRI);            /* save current address in PRI */
-    rvalue(lval);               /* get the symbol's value in PRI */
+    if (lval->ident!=iACCESSOR)
+      rvalue(lval);               /* get the symbol's value in PRI */
   } /* if */
 
   assert(!savepri || !savealt); /* either one MAY be set, but not both */
@@ -277,8 +278,10 @@ static void (*unopers[])(void) = { lneg, neg, user_inc, user_dec };
     assert(lval!=NULL);
     if (lval->ident==iARRAYCELL || lval->ident==iARRAYCHAR)
       popreg(sALT);             /* restore address (in ALT) */
-    store(lval);                /* store PRI in the symbol */
-    moveto1();                  /* make sure PRI is restored on exit */
+    if (lval->ident!=iACCESSOR) {
+      store(lval);                /* store PRI in the symbol */
+      moveto1();                  /* make sure PRI is restored on exit */
+    }
   } /* if */
   return TRUE;
 }
@@ -1901,10 +1904,15 @@ static int hier2(value *lval)
         } else {
           pushreg(sPRI);    // save obj
           invoke_getter(lval->accessor);
-          swap1();          // pri = obj, stack = [oldval]
-          pushreg(sPRI);    // pri = obj, stack = [oldval, obj]
+          move_alt();     // alt = oldval
+          swap1();        // pri = saved obj, stack = [oldval]
+          pushreg(sPRI);  // pri = obj, alt = oldval, stack = [obj, oldval]
+          moveto1();      // pri = oldval, stack = [obj, oldval]
+
+          // check_userop on an iACCESSOR acts as though the value is an rvalue.
           if (!check_userop(user_inc, lval->tag, 0, 1, lval, &lval->tag))
             inc_pri();
+
           popreg(sALT);
           invoke_setter(lval->accessor, FALSE);
           popreg(sPRI);
@@ -1932,10 +1940,15 @@ static int hier2(value *lval)
         } else {
           pushreg(sPRI);    // save obj
           invoke_getter(lval->accessor);
-          swap1();          // pri = obj, stack = [oldval]
-          pushreg(sPRI);    // pri = obj, stack = [oldval, obj]
+          move_alt();     // alt = oldval
+          swap1();        // pri = saved obj, stack = [oldval]
+          pushreg(sPRI);  // pri = obj, alt = oldval, stack = [obj, oldval]
+          moveto1();      // pri = oldval, stack = [obj, oldval]
+
+          // check_userop on an iACCESSOR acts as though the value is an rvalue.
           if (!check_userop(user_dec, lval->tag, 0, 1, lval, &lval->tag))
             dec_pri();
+
           popreg(sALT);
           invoke_setter(lval->accessor, FALSE);
           popreg(sPRI);
diff --git a/sourcepawn/compiler/sc4.c b/sourcepawn/compiler/sc4.c
index 70c6f06f..e7f00d23 100644
--- a/sourcepawn/compiler/sc4.c
+++ b/sourcepawn/compiler/sc4.c
@@ -1394,6 +1394,12 @@ SC_FUNC void jmp_eq0(int number)
   code_idx+=opcodes(1)+opargs(1);
 }
 
+SC_FUNC void xchg(void)
+{
+  stgwrite("\txchg\n");
+  code_idx+=opcodes(1);
+}
+
 /* write a value in hexadecimal; optionally adds a newline */
 SC_FUNC void outval(cell val,int newline)
 {