From 284667c18fb8765d0c74d40c4d75b57feaed1a1f Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Fri, 18 Dec 2020 09:44:22 +0000
Subject: [PATCH] Fix BTG error reporting

Use gzerror, not strerror, for these codes.
---
 simgear/io/sg_binobj.cxx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/simgear/io/sg_binobj.cxx b/simgear/io/sg_binobj.cxx
index 5e4e5b1a..4d6180c1 100644
--- a/simgear/io/sg_binobj.cxx
+++ b/simgear/io/sg_binobj.cxx
@@ -566,8 +566,10 @@ bool SGBinObject::read_bin( const SGPath& file ) {
     sgReadUInt( fp, &header );
 
     if (sgReadError()) {
+        int code = 0;
+        const char* gzErrorString = gzerror(fp, &code);
         gzclose(fp);
-        throw sg_io_exception("Unable to read BTG header: " + simgear::strutils::error_string(errno), sg_location(file));
+        throw sg_io_exception("Unable to read BTG header: " + string{gzErrorString} + ", code =" + std::to_string(code), sg_location(file));
     }
 
     if ( ((header & 0xFF000000) >> 24) == 'S' &&