[svn-r18657] I added some comments. No test is needed.

1 files changed, 18 insertions, 2 deletions

diff --git a/src/H5Tnative.c b/src/H5Tnative.c
index ce2c141..5b685b1 100644
--- a/src/H5Tnative.c
+++ b/src/H5Tnative.c
@@ -317,8 +317,24 @@ H5T_get_native_type(H5T_t *dtype, H5T_direction_t direction, size_t *struct_alig
                         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "cannot insert member to compound datatype")
                 }
 
-                /* Update size, offset and compound alignment for parent in the case of 
-                 * nested compound type. */
+                /* Update size, offset and compound alignment for parent in the case of
+                 * nested compound type.  The alignment for a compound type as one field in
+                 * a compound type is the biggest compound alignment among all its members.
+                 * i.g. in the structure
+                 *    typedef struct s1 {
+                 *        char            c;
+                 *        int             i;
+                 *        s2              st;
+                 *        unsigned long long       l;
+                 *    } s1;
+                 *    typedef struct s2 {
+                 *        short           c2;
+                 *        long            l2;
+                 *        long long       ll2;
+                 *    } s2;
+                 * The alignment for ST in S1 is the biggest structure alignment of all the
+                 * members of S2, which is probably the LL2 of 'long long'. -SLU 2010/4/28
+                 */
                 if(H5T_cmp_offset(comp_size, offset, children_size, (size_t)1, children_st_align,
                                   struct_align) < 0)
                     HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "cannot compute compound offset")