From 4b68d19993c41da4f77342e8bc4dea74a9d4f80c Mon Sep 17 00:00:00 2001
From: Kugel Fuhr <98353208+kugelfuhr@users.noreply.github.com>
Date: Sun, 1 Sep 2024 10:42:18 +0200
Subject: [PATCH] Fix issue #1663.

---
 src/ca65/condasm.c | 72 +++++++++++++++++++++++++---------------------
 1 file changed, 40 insertions(+), 32 deletions(-)

diff --git a/src/ca65/condasm.c b/src/ca65/condasm.c
index 6198f4017..f872ec9ed 100644
--- a/src/ca65/condasm.c
+++ b/src/ca65/condasm.c
@@ -133,24 +133,26 @@ static void SetIfCond (IfDesc* ID, int C)
 
 
 
-static void ElseClause (IfDesc* ID, const char* Directive)
-/* Enter an .ELSE clause */
+static int ElseClause (IfDesc* ID, const char* Directive)
+/* Enter an .ELSE clause. Return true if this was ok, zero on errors. */
 {
     /* Check if we have an open .IF - otherwise .ELSE is not allowed */
     if (ID == 0) {
         Error ("Unexpected %s", Directive);
-        return;
+        return 0;
     }
 
     /* Check for a duplicate else, then remember that we had one */
     if (ID->Flags & ifElse) {
         /* We already had a .ELSE ! */
         Error ("Duplicate .ELSE");
+        return 0;
     }
     ID->Flags |= ifElse;
 
     /* Condition is inverted now */
     ID->Flags ^= ifCond;
+    return 1;
 }
 
 
@@ -226,46 +228,52 @@ void DoConditionals (void)
                 D = GetCurrentIf ();
 
                 /* Allow an .ELSE */
-                ElseClause (D, ".ELSE");
+                if (ElseClause (D, ".ELSE")) {
+                    /* Remember the data for the .ELSE */
+                    if (D) {
+                        ReleaseFullLineInfo (&D->LineInfos);
+                        GetFullLineInfo (&D->LineInfos);
+                        D->Name = ".ELSE";
+                    }
 
-                /* Remember the data for the .ELSE */
-                if (D) {
-                    ReleaseFullLineInfo (&D->LineInfos);
-                    GetFullLineInfo (&D->LineInfos);
-                    D->Name = ".ELSE";
+                    /* Calculate the new overall condition */
+                    CalcOverallIfCond ();
+
+                    /* Skip .ELSE */
+                    NextTok ();
+                    ExpectSep ();
+                } else {
+                    /* Problem with .ELSE, ignore remainder of line */
+                    SkipUntilSep ();
                 }
-
-                /* Calculate the new overall condition */
-                CalcOverallIfCond ();
-
-                /* Skip .ELSE */
-                NextTok ();
-                ExpectSep ();
                 break;
 
             case TOK_ELSEIF:
                 D = GetCurrentIf ();
                 /* Handle as if there was an .ELSE first */
-                ElseClause (D, ".ELSEIF");
+                if (ElseClause (D, ".ELSEIF")) {
+                    /* Calculate the new overall if condition */
+                    CalcOverallIfCond ();
 
-                /* Calculate the new overall if condition */
-                CalcOverallIfCond ();
+                    /* Allocate and prepare a new descriptor */
+                    D = AllocIf (".ELSEIF", 0);
+                    NextTok ();
 
-                /* Allocate and prepare a new descriptor */
-                D = AllocIf (".ELSEIF", 0);
-                NextTok ();
+                    /* Ignore the new condition if we are inside a false .ELSE
+                    ** branch. This way we won't get any errors about undefined
+                    ** symbols or similar...
+                    */
+                    if (IfCond) {
+                        SetIfCond (D, ConstExpression ());
+                        ExpectSep ();
+                    }
 
-                /* Ignore the new condition if we are inside a false .ELSE
-                ** branch. This way we won't get any errors about undefined
-                ** symbols or similar...
-                */
-                if (IfCond) {
-                    SetIfCond (D, ConstExpression ());
-                    ExpectSep ();
+                    /* Get the new overall condition */
+                    CalcOverallIfCond ();
+                } else {
+                    /* Problem with .ELSEIF, ignore remainder of line */
+                    SkipUntilSep ();
                 }
-
-                /* Get the new overall condition */
-                CalcOverallIfCond ();
                 break;
 
             case TOK_ENDIF: