From 3649041195bac6494bdcd269872a06a11184df79 Mon Sep 17 00:00:00 2001
From: John Reiser <jreiser@BitWagon.com>
Date: Mon, 19 Dec 2022 13:37:24 -0800
Subject: [PATCH] Return value of FileBase::seek(, SEEK_CUR) was not
 FileBase::tell()

	modified:   file.cpp
---
 src/file.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/file.cpp b/src/file.cpp
index 5cae7755..6e6c0d7f 100644
--- a/src/file.cpp
+++ b/src/file.cpp
@@ -117,6 +117,7 @@ void FileBase::closex() {
         throwIOException("close failed", errno);
 }
 
+// Return value of ::seek is the resulting file offset (same as ::tell())
 upx_off_t FileBase::seek(upx_off_t off, int whence) {
     if (!isOpen())
         throwIOException("bad seek 1");
@@ -132,9 +133,11 @@ upx_off_t FileBase::seek(upx_off_t off, int whence) {
         off += _offset + _length;
         whence = SEEK_SET;
     }
-    if (::lseek(_fd, off, whence) < 0)
+    // SEEK_CUR falls through to here
+    upx_off_t rv = ::lseek(_fd, off, whence);
+    if (0 == (1+ rv))  // lazy coding to check for "-1" failure of ::lseek
         throwIOException("seek error", errno);
-    return off - _offset;
+    return rv - _offset;
 }
 
 upx_off_t FileBase::tell() const {