OSF DCE Application Development Guide--Core Components

The DCE Backing Store
5.5.2 Conformant Arrays Not Allowed
You cannot use conformant arrays in objects stored to a backing store. This is because
the IDL-generated code that encodes (pickles) the structure has no way to predict or
detect the size of the array. When the object is fetched, there will likely be insufficient
space provided for the structure, and the array’s data will destroy whatever is in memory
after the structure.
To illustrate the problem more clearly, here is an example. An IDL file has a conformant
array, na , as an object in a struct:
typedef struct {
unsigned32 length;
[size_is(length)]
unsigned32 numbers[];
} num_array_t
typedef struct {
char *name;
num_array_t na;
} my_type_t;
The idl compiler turns the IDL specification into the following .h file contents:
typedef struct {
unsigned32 length;
unsigned32 numbers[1];
} num_array_t
typedef struct {
idl_char *name;
num_array_t na;
} my_type_t;
When the object is fetched, and the array length is greater than the 1 (one) assumed in
the .h file, the decoding operation destroys whatever follows my_struct in memory:
my_type_t my_struct;
dce_db_fetch(dbh, key, &my_struct, &st);
The correct method is to use a pointer to the array, not the array itself, in the IDL file.
For example:
typedef struct {
char *name;
num_array_t *na;
} my_type_t;
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