From 4fc19a3d4c27d193297e928171f85ab361ac2ae7 Mon Sep 17 00:00:00 2001
From: bbbradsmith <bbbradsmith@users.noreply.github.com>
Date: Sun, 19 Feb 2023 08:37:07 -0500
Subject: [PATCH] ld65 overwrite segment should pad with fill value if the
 desired seek position is beyond the end of the file so far

---
 src/ld65/bin.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/ld65/bin.c b/src/ld65/bin.c
index bd822cc23..15b534f66 100644
--- a/src/ld65/bin.c
+++ b/src/ld65/bin.c
@@ -193,8 +193,16 @@ static void BinWriteMem (BinDesc* D, MemoryArea* M)
                     NewAddr += M->Start;
                 }
                 if (DoWrite || (M->Flags & MF_FILL) != 0) {
-                    /* Seek in "overwrite" segments */
                     if (S->Flags & SF_OVERWRITE) {
+                        /* Seek in "overwrite" segments. Fill if the seek position has not been reached yet. */
+                        unsigned long FileLength;
+                        unsigned long SeekTarget = NewAddr - M->Start + M->FileOffs;
+                        fseek (D->F, 0, SEEK_END);
+                        FileLength = ftell (D->F);
+                        if (SeekTarget > FileLength) {
+                            WriteMult (D->F, M->FillVal, SeekTarget - FileLength);
+                            PrintNumVal ("SF_OVERWRITE", SeekTarget - FileLength);
+                        }
                         fseek (D->F, NewAddr - M->Start + M->FileOffs, SEEK_SET);
                     } else {
                         WriteMult (D->F, M->FillVal, NewAddr-Addr);