[Glass] FFI and C subsystems

[bruno buzzi brassesco]

James,

It seems that is possible to create a new header file and includes 2 
subsystems in the same GS Library.

For example sftp_server_all.h:
#include "libssh.h"
#include "server.h"
#include "sftp.h"

Then:
| header wrapperClass wrapper |
header := CHeader path: 'sftp_server_all.h'.
wrapperClass := header wrapperForLibraryAt:
'/usr/lib64/libssh.so.4.4.0'.
wrapperClass initializeFunctions.
UserGlobals at: wrapperClass name put: wrapperClass.

Do you see any problem with this approach ?

The new library generated all functions now i going to check if they work.
It should work i think ... (but again not a C expert -dealing with C 
again after 15 years-)



regards,
Bruno

On 9/10/2020 14:53, James Foster via Glass wrote:
> Bruno,
>
> My understanding is that the header parser follows all the #include 
> directives, so will find everything that could be called from C code, 
> including abs() in libc. But the process of calling a dynamic library 
> at runtime involves doing a name lookup of entry points *for that 
> library,* not for anything visible *to* the library, so libssh does 
> not have an abs() entry point. For that you would need a reference to 
> libc.
>
> The wrapper generator does not know what is actually in the given 
> library, just what functions are defined by all included header files. 
> So you have to do some selection on your own. One wrapper API has a 
> filter as an argument, and so for a library like GemStone C Interface 
> where all the functions begin with ‘gci’ we can filter to only 
> generate wrappers for those functions (it is unlikely that libc has 
> gci*() functions!).
>
> So, yes, you need to have a different library object for each library 
> so the system can do name lookups properly.
>
> James
>
>> On Oct 9, 2020, at 5:40 AM, Bruno Buzzi Brassesco via Glass 
>> <glass at lists.gemtalksystems.com 
>> <mailto:glass at lists.gemtalksystems.com>> wrote:
>>
>> Hi,
>> Maybe i'm wrong in some concepts here (not a C expert) but ...
>>
>> If a C library (libssh) has a subsystem (sftp) in order to create a 
>> GS wrapper i can do:
>>
>>     | header wrapperClass wrapper |
>>     header := CHeader path: '/usr/include/libssh/sftp.h'.
>>     wrapperClass := header wrapperForLibraryAt:
>>     '/usr/lib64/libssh.so.4.4.0'.
>>     wrapperClass initializeFunctions.
>>     UserGlobals at: wrapperClass name put: wrapperClass.
>>
>>
>> In this case I got all the functions of Libssh and also SFTP, so far 
>> so good.
>>
>> But what happens when there is more than one C subsystem?
>>
>> How can I generate only one GS wrapper for the original C library 
>> (libssh) and all its subsystems ?
>> Or I will have to create one wrapper per subsystem ?
>>
>> regards,
>> bruno
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>
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