From ac93f2dd10537cc3c344a1d44d2914e4343b4085 Mon Sep 17 00:00:00 2001
From: "John J. Camilleri" <john@digitalgrammars.com>
Date: Mon, 18 Oct 2021 13:54:13 +0200
Subject: [PATCH] Don't call msync in PgfDB::sync on macOS

---
 src/runtime/c/pgf/db.cxx | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/runtime/c/pgf/db.cxx b/src/runtime/c/pgf/db.cxx
index 6e0e80d5f..4450c29fc 100644
--- a/src/runtime/c/pgf/db.cxx
+++ b/src/runtime/c/pgf/db.cxx
@@ -1077,7 +1077,13 @@ void PgfDB::sync()
     size_t size =
         ms->top + chunksize(ptr(ms,ms->top)) + sizeof(size_t);
 
-    int res = msync((void *) ms, size, MS_SYNC | MS_INVALIDATE);
+    int res;
+#ifndef MREMAP_MAYMOVE
+    if (current_db->fd < 0) {
+      res = 0;
+    } else
+#endif
+    res = msync((void *) ms, size, MS_SYNC | MS_INVALIDATE);
     if (res != 0)
         throw pgf_systemerror(errno);
 }