From b0d6fc70b4e1f0f0e7552d6851b3efc0b91e62bd Mon Sep 17 00:00:00 2001
From: uweschulzweida <35592488+uweschulzweida@users.noreply.github.com>
Date: Wed, 5 Apr 2023 18:05:53 +0200
Subject: [PATCH] Fix issue #2674

---
 libhdf5/hdf5open.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/libhdf5/hdf5open.c b/libhdf5/hdf5open.c
index cb2491ff9f..e00f426ef6 100644
--- a/libhdf5/hdf5open.c
+++ b/libhdf5/hdf5open.c
@@ -1205,12 +1205,14 @@ static int get_quantize_info(NC_VAR_INFO_T *var)
 {
     hid_t attid;
     hid_t datasetid;
+    htri_t attr_exists;
 
     /* Try to open an attribute of the correct name for quantize
      * info. */
     datasetid = ((NC_HDF5_VAR_INFO_T *)var->format_var_info)->hdf_datasetid;
-    attid = H5Aopen_by_name(datasetid, ".", NC_QUANTIZE_BITGROOM_ATT_NAME,
-			    H5P_DEFAULT, H5P_DEFAULT);
+    attr_exists = H5Aexists(datasetid, NC_QUANTIZE_BITGROOM_ATT_NAME);
+    attid = attr_exists ? H5Aopen_by_name(datasetid, ".", NC_QUANTIZE_BITGROOM_ATT_NAME,
+			    H5P_DEFAULT, H5P_DEFAULT) : 0;
 
     if (attid > 0)
       {
@@ -1218,16 +1220,18 @@ static int get_quantize_info(NC_VAR_INFO_T *var)
       }
     else
       {
-	attid = H5Aopen_by_name(datasetid, ".", NC_QUANTIZE_GRANULARBR_ATT_NAME,
-			    H5P_DEFAULT, H5P_DEFAULT);
+        attr_exists = H5Aexists(datasetid, NC_QUANTIZE_GRANULARBR_ATT_NAME);
+	attid = attr_exists ? H5Aopen_by_name(datasetid, ".", NC_QUANTIZE_GRANULARBR_ATT_NAME,
+			    H5P_DEFAULT, H5P_DEFAULT) : 0;
 	if (attid > 0)
 	  {
 	    var->quantize_mode = NC_QUANTIZE_GRANULARBR;
 	  }
 	else
 	  {
-	    attid = H5Aopen_by_name(datasetid, ".", NC_QUANTIZE_BITROUND_ATT_NAME,
-				    H5P_DEFAULT, H5P_DEFAULT);
+            attr_exists = H5Aexists(datasetid, NC_QUANTIZE_BITROUND_ATT_NAME);
+	    attid = attr_exists ? H5Aopen_by_name(datasetid, ".", NC_QUANTIZE_BITROUND_ATT_NAME,
+				    H5P_DEFAULT, H5P_DEFAULT) : 0;
 	    if (attid > 0)
 	      var->quantize_mode = NC_QUANTIZE_BITROUND;
 	  }