Fix issue where H5Tset_fields does not account for datatype offsets (#4061)

H5Tset_fields did not account for any offset in a floating-point datatype,
causing it to fail when a datatype's precision is correctly set such that
it doesn't include the offset bits.

release_docs/RELEASE.txt

@@ -489,6 +489,16 @@ Bug Fixes since HDF5-1.14.0 release
 ===================================
     Library
     -------
+    - Fixed a bug where H5Tset_fields does not account for any offset
+      set for a floating-point datatype when determining if values set
+      for spos, epos, esize, mpos and msize make sense for the datatype
+
+      Previously, H5Tset_fields did not take datatype offsets into account
+      when determining if the values set make sense for the datatype.
+      This would cause the function to fail when the precision for a
+      datatype is correctly set such that the offset bits are not included.
+      This has now been fixed.
+
     - Fixed H5Fget_access_plist so that it returns the file locking
       settings for a file
 

src/H5Tfloat.c

@@ -106,11 +106,11 @@ H5Tset_fields(hid_t type_id, size_t spos, size_t epos, size_t esize, size_t mpos
         dt = dt->shared->parent; /*defer to parent*/
     if (H5T_FLOAT != dt->shared->type)
         HGOTO_ERROR(H5E_DATATYPE, H5E_BADTYPE, FAIL, "operation not defined for datatype class");
-    if (epos + esize > dt->shared->u.atomic.prec)
+    if (epos + esize - dt->shared->u.atomic.offset > dt->shared->u.atomic.prec)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "exponent bit field size/location is invalid");
-    if (mpos + msize > dt->shared->u.atomic.prec)
+    if (mpos + msize - dt->shared->u.atomic.offset > dt->shared->u.atomic.prec)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "mantissa bit field size/location is invalid");
-    if (spos >= dt->shared->u.atomic.prec)
+    if (spos - dt->shared->u.atomic.offset >= dt->shared->u.atomic.prec)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "sign location is not valid");
 
     /* Check for overlap */

test/dtypes.c

@@ -4156,6 +4156,89 @@ error:
     return 1;
 }
 
+/*-------------------------------------------------------------------------
+ * Function:    test_set_fields_offset
+ *
+ * Purpose:     Tests for a bug in H5Tset_fields in which the function
+ *              didn't account for an offset set for a floating-point
+ *              datatype when checking whether the values set for the
+ *              floating-point fields make sense for the datatype.
+ *
+ * Return:      Success:    0
+ *              Failure:    number of errors
+ *
+ *-------------------------------------------------------------------------
+ */
+static int
+test_set_fields_offset(void)
+{
+    hid_t tid = H5I_INVALID_HID;
+
+    if ((tid = H5Tcopy(H5T_NATIVE_FLOAT)) < 0) {
+        H5_FAILED();
+        printf("Can't copy datatype\n");
+        goto error;
+    }
+
+    /* Create a custom 128-bit floating-point datatype */
+    if (H5Tset_size(tid, 16) < 0) {
+        H5_FAILED();
+        printf("Can't set datatype size\n");
+        goto error;
+    }
+
+    /* We will have 7 bytes of MSB padding + 5 bytes of offset padding */
+    if (H5Tset_precision(tid, 116) < 0) {
+        H5_FAILED();
+        printf("Can't set datatype size\n");
+        goto error;
+    }
+
+    if (H5Tset_offset(tid, 5) < 0) {
+        H5_FAILED();
+        printf("Can't set datatype offset\n");
+        goto error;
+    }
+
+    if (H5Tset_ebias(tid, 16383) < 0) {
+        H5_FAILED();
+        printf("Can't set datatype exponent bias\n");
+        goto error;
+    }
+
+    /*
+     * Floating-point type with the following:
+     *
+     *   - 5 bits of LSB padding (bits 0 - 4)
+     *   - 100-bit mantissa starting at bit 5
+     *   - 15-bit exponent starting at bit 105
+     *   - 1 sign bit at bit 120
+     *   - 7 bits of MSB padding
+     */
+    if (H5Tset_fields(tid, 120, 105, 15, 5, 100) < 0) {
+        H5_FAILED();
+        printf("Can't set datatype's floating-point fields\n");
+        goto error;
+    }
+
+    if (H5Tclose(tid) < 0) {
+        H5_FAILED();
+        printf("Can't close datatype\n");
+        goto error;
+    }
+
+    return 0;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Tclose(tid);
+    }
+    H5E_END_TRY;
+
+    return 1;
+}
+
 /*-------------------------------------------------------------------------
  * Function:    test_transient
  *
@@ -9032,6 +9115,7 @@ main(void)
     nerrors += test_detect();
     nerrors += test_compound_1();
     nerrors += test_query();
+    nerrors += test_set_fields_offset();
     nerrors += test_transient(fapl);
     nerrors += test_named(fapl);
     nerrors += test_encode();