The CORBA policy for parameter memory management

When a class contains the SOM IDL modifier memory_management = corba, this signifies that all methods introduced by the class follow the CORBA specification for parameter memory management, except where a particular method has an explicit modifier (object_owns_result or object_owns_parameters) that indicates otherwise. The remainder of this section describes the CORBA specification for parameter memory management.

Caller frees parameters and return results

The CORBA memory-management policy specifies that the caller of a method is responsible for freeing all parameters and the return result after the method call is complete. This applies regardless of whether the parameter was allocated by the caller or the object (or, in the case of a remote method call, by DSOM). In other words, the CORBA policy asserts that parameters are uniformly "caller-owned".

Allocation responsibilities

Whether the parameter or return result should be allocated by the caller or by the object depends on the type of the parameter and its mode ("in", "inout", "out", or "return"). In general, the caller is responsible for allocating storage for most parameters and return results. More specifically, CORBA requires that storage for all "in" arguments, for all "inout" or "out" arguments, and for all "return" results must be provided by the client program, with certain exceptions as itemized below.

The object is responsible for allocating storage as follows:

• for strings when used as "out" arguments or as "return" results

• for the "_buffer" field of sequences when used as "out" arguments or as "return" results,

• for the "_value" field of anys when used as "inout" or "out" arguments or as "return" results,

• for pointer types when used as "inout" or "out" arguments or as "return" results,

• for arrays when used as "return" results, and

• for objects when used as "inout" or "out" arguments or as "return" results.

Note: For "inout" strings and sequences, the "out" result is constrained to be no larger than the size of the "in" argument allocated by the client.

Ownership of memory allocated in the above cases becomes the responsibility of the client program. For remote method calls, when a remote object allocates memory for a parameter or "return" value, DSOM subsequently allocates memory in the client's address space for the parameter or result. For a parameter/result that is an object (rather than a block of memory) DSOM automatically creates an object reference (a proxy object) in the client's address space. In each case, the memory or the proxy object becomes the responsibility of the client program and should later be freed by the client, using ORBfree for blocks of memory or release for proxy objects.