Developer forum
cancel
Showing results for 
Search instead for 
Did you mean: 

ACAPI_LibPart_SetDetails_ParamDef function signature

Anonymous
Not applicable
Hello,

the function signature of ACAPI_LibPart_SetDetails_ParamDef looks like this:

ACAPI_LibPart_GetSect_ParamDef (const API_LibPart *libPart, API_AddParType **addPars, double*a, double*b, GSHandle sect2DDrawHdl, GSHandle *sectionHdl, GS::UniString *password = nullptr);
Why is the type of the 2nd argument API_AddParType**? It looks like the function is actually expecting a GSHandle. If we try to use anything other than a GSHandle, for example a local array, our code breaks. Unfortunately the documentation only says
[in] Additive parameters of the Library Part

which is not very helpful.

Do we really need a GSHandle here? If so, are there other API functions that use such double pointers and expect a GSHandle?
1 ACCEPTED SOLUTION

Solution
Ralph Wessel
Mentor
A double pointer, or pointer to a pointer, is sometimes referred to as a "handle". GSHandle is is just an alias for the same thing, i.e. they are all actually synonymous. And yes, there are many more cases like this. You can use functions like BMGetHandleSize to get size allocated to the handle.
Ralph Wessel BArch

View solution in original post

3 REPLIES 3

Solution
Ralph Wessel
Mentor
A double pointer, or pointer to a pointer, is sometimes referred to as a "handle". GSHandle is is just an alias for the same thing, i.e. they are all actually synonymous. And yes, there are many more cases like this. You can use functions like BMGetHandleSize to get size allocated to the handle.
Ralph Wessel BArch

Anonymous
Not applicable
Thanks for the clarification. We're aware that GSHandle is just a char** as well. We just didn't know whether we had to allocate an actual handle (-> BMAllocateHandle) or not. A pointer to pointer could also be a pointer to an array or an array of pointers. This gets especially confusing if the same function signature uses both variants API_AddParType** and later GSHandle at the same time. The type alias at least makes it clear that we need a proper handle.

Ralph Wessel
Mentor
That's true - it's not so easy to distinguish – particularly if the documentation isn't explicit. Generally speaking, a pointer to a pointer will be allocated as a handle, but there are exceptions. Best approach is to look at the example code with the dev-kit and see what they do. Otherwise, you can only run tests by calling functions that expect a handle and see if they fail.
Ralph Wessel BArch

Still looking?

Browse more topics

Back to forum

See latest solutions

Accepted solutions

Start a new discussion!