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UFFI Problem: A call to an external function failed (FFIOpaqueObject)

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Georg Hagn

UFFI Problem: A call to an external function failed (FFIOpaqueObject)

For an exercise with uFFi i am try an C-Connector for MariaDB like
Garage or UBDC
As in "Unified FFI Februar 12 2020" I made Helper-classes:

FFILibrary subclass: #MariaDBLibC

FFIOpaqueObject subclass: #MariaDBHandle
MariaDBHandle >> unixModuleName [
^ '/usr/lib/x86_64-linux-gnu/libmariadb.so'
]

and a class

Object subclass: #MariaDBDriver
instanceVariableNames: 'connectionHandle'

"Accessors"
MariaDBDriver >> connectionHandle [ ^ connectionHandle ]
MariaDBDriver >> connectionHandle: aHandle [ connectionHandle := aHandle ]
MariaDBDriver class >> ffiLibrary [ ^ MariaDBLibC ]

"API Methods"
MariaDBDriver >> clientInfo [ ^ self class clientInfo ]

MariaDBDriver class >> clientInfo [
^ self ffiCall: #(String mysql_get_client_info(void))
]

For a first simple Test I choosed the c-api-funtion:
„const char * mysql_get_client_info(void )“

In Playground I executed:
driver := MariaDBDriver fromConnectionString:
'mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest'.

driver clientInfo inspect.
And I get the expected result: String „10.2.9“

But the second test with c-api-funtcion fails
„MYSQL * mysql_init(NULL)“

MariaDBDriver >> init [
| aNullHandle |
aNullHandle := ExternalAddress null.
self connectionHandle: (self class init: aNullHandle).
]

MariaDBDriver class >> init: aNullHandle [
^ self ffiCall: #(MariaDBHandle * mysql_init(ExternalAddress aNullHandle)).
]

In Playground I again executed:
driver := MariaDBDriver fromConnectionString:
'mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest'.

driver init inspect.
" A call to an external function failed"

Any ideas what is wrong??

Thanks
Georg

Stéphane Ducasse

Re: UFFI Problem: A call to an external function failed (FFIOpaqueObject)

Hello Georg

This is a great news. since we need more binding.

I do not really know the answer but I’m sure the guys will help you.

Now just a question: what is the definition of MYSQL

that you mentioned in

„MYSQL * mysql_init(NULL)“

On 21 Jun 2020, at 11:27, Georg Hagn <[hidden email]> wrote:

For an exercise with uFFi i am try an C-Connector for MariaDB like
Garage or UBDC
As in "Unified FFI Februar 12 2020" I made Helper-classes:

FFILibrary subclass: #MariaDBLibC

FFIOpaqueObject subclass: #MariaDBHandle
MariaDBHandle >> unixModuleName [
  ^ '/usr/lib/x86_64-linux-gnu/libmariadb.so'
]

and a class

Object subclass: #MariaDBDriver
  instanceVariableNames: 'connectionHandle'

"Accessors"
MariaDBDriver >> connectionHandle [ ^ connectionHandle ]
MariaDBDriver >> connectionHandle: aHandle [ connectionHandle := aHandle ]
MariaDBDriver class >> ffiLibrary [   ^ MariaDBLibC ]

"API Methods"
MariaDBDriver >> clientInfo [ ^ self class clientInfo ]

MariaDBDriver class >> clientInfo [
  ^ self ffiCall: #(String mysql_get_client_info(void))
]

For a first simple Test I choosed the c-api-funtion:
„const char * mysql_get_client_info(void )“

In Playground I executed:
driver := MariaDBDriver fromConnectionString:
'<a href="mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest" class="">mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest'.

driver clientInfo inspect.
And I get the expected result: String „10.2.9“

But the second test with c-api-funtcion fails
„MYSQL * mysql_init(NULL)“

MariaDBDriver >> init [
  | aNullHandle |
  aNullHandle := ExternalAddress null.
  self connectionHandle: (self class init: aNullHandle).
]

MariaDBDriver class >> init: aNullHandle [
  ^ self ffiCall: #(MariaDBHandle * mysql_init(ExternalAddress aNullHandle)).
]

In Playground I again executed:
driver := MariaDBDriver fromConnectionString:
'<a href="mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest" class="">mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest'.

driver init inspect.
" A call to an external function failed"

Any ideas what is wrong??

Thanks
Georg

--------------------------------------------

Stéphane Ducasse

http://stephane.ducasse.free.fr / http://www.pharo.org

03 59 35 87 52

Assistant: Aurore Dalle

FAX 03 59 57 78 50

TEL 03 59 35 86 16

S. Ducasse - Inria

40, avenue Halley,

Parc Scientifique de la Haute Borne, Bât.A, Park Plaza

Villeneuve d'Ascq 59650

France

Georg Hagn

Re: UFFI Problem: A call to an external function failed (FFIOpaqueObject)

Hello Stephane,

Definition from: https://mariadb.com/kb/en/mariadb-connectorc-data-structures :
"The MYSQL structure represents one database connection and is used by
most of MariaDB Connector/C's API functions. The MYSQL structure needs
to be allocated and initialized by the mysql_init() API function. It
will be released by the mysql_close() function. The MYSQL structure
should be considered as opaque."

I try with MariaDB, because there is a valid mysql binding. I can test
my UFFi Connector agains MySQL. BTW, I use Pharo 8.0

Georg Hagn

Am So., 21. Juni 2020 um 16:12 Uhr schrieb Stéphane Ducasse
<[hidden email]>:

>
> Hello Georg
>
> This is a great news. since we need more binding.
> I do not really know the answer but I’m sure the guys will help you.
> Now just a question: what is the definition of MYSQL
> that you mentioned in
> „MYSQL * mysql_init(NULL)“
>
>
> S.
>
> On 21 Jun 2020, at 11:27, Georg Hagn <[hidden email]> wrote:
>
> For an exercise with uFFi i am try an C-Connector for MariaDB like
> Garage or UBDC
> As in "Unified FFI Februar 12 2020" I made Helper-classes:
>
> FFILibrary subclass: #MariaDBLibC
>
> FFIOpaqueObject subclass: #MariaDBHandle
> MariaDBHandle >> unixModuleName [
> ^ '/usr/lib/x86_64-linux-gnu/libmariadb.so'
> ]
>
> and a class
>
> Object subclass: #MariaDBDriver
> instanceVariableNames: 'connectionHandle'
>
> "Accessors"
> MariaDBDriver >> connectionHandle [ ^ connectionHandle ]
> MariaDBDriver >> connectionHandle: aHandle [ connectionHandle := aHandle ]
> MariaDBDriver class >> ffiLibrary [ ^ MariaDBLibC ]
>
> "API Methods"
> MariaDBDriver >> clientInfo [ ^ self class clientInfo ]
>
> MariaDBDriver class >> clientInfo [
> ^ self ffiCall: #(String mysql_get_client_info(void))
> ]
>
> For a first simple Test I choosed the c-api-funtion:
> „const char * mysql_get_client_info(void )“
>
> In Playground I executed:
> driver := MariaDBDriver fromConnectionString:
> 'mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest'.
>
> driver clientInfo inspect.
> And I get the expected result: String „10.2.9“
>
> But the second test with c-api-funtcion fails
> „MYSQL * mysql_init(NULL)“
>
> MariaDBDriver >> init [
> | aNullHandle |
> aNullHandle := ExternalAddress null.
> self connectionHandle: (self class init: aNullHandle).
> ]
>
> MariaDBDriver class >> init: aNullHandle [
> ^ self ffiCall: #(MariaDBHandle * mysql_init(ExternalAddress aNullHandle)).
> ]
>
> In Playground I again executed:
> driver := MariaDBDriver fromConnectionString:
> 'mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest'.
>
> driver init inspect.
> " A call to an external function failed"
>
> Any ideas what is wrong??
>
> Thanks
> Georg
>
>
> --------------------------------------------
> Stéphane Ducasse
> http://stephane.ducasse.free.fr / http://www.pharo.org
> 03 59 35 87 52
> Assistant: Aurore Dalle
> FAX 03 59 57 78 50
> TEL 03 59 35 86 16
> S. Ducasse - Inria
> 40, avenue Halley,
> Parc Scientifique de la Haute Borne, Bât.A, Park Plaza
> Villeneuve d'Ascq 59650
> France
>

Pierce Ng-3

Re: UFFI Problem: A call to an external function failed (FFIOpaqueObject)

In reply to this post by Georg Hagn

On Sun, Jun 21, 2020 at 11:27:22AM +0200, Georg Hagn wrote:
> 'mariaDB://localhost:5432/sodbxtest?&user=sodbxtest&password=sodbxtest'.

Hi,

Firstly, 5432 is PostgreSQL. MySQL/MariaDB default port is 3306.

Just a note, as mysql_init() only allocates the C level structure and
doesn't connect.

> FFILibrary subclass: #MariaDBLibC
>
> FFIOpaqueObject subclass: #MariaDBHandle
> MariaDBHandle >> unixModuleName [
> ^ '/usr/lib/x86_64-linux-gnu/libmariadb.so'
> ]

With your code, implementing #unixModuleName in MariaDBLibC works for
me. I've never done that in FFIOpaqueObject subclasses.

In terms of organizing code, suggest you implement the FFI calls in
MariaDBLibC itself and do away with MariaDBDriver. Having the FFI calls
in MariaDBDriver while using MariaDBLibC only for locating the C
libraries is using two classes where one will do.

Finally, there is a non FFI pure Smalltalk implementation of the MySQL
wire protocol that has been around a while. If you are doing this FFI
thing for practice, I recommend that you wrap another C library, so that
when you are done, Pharo gets another C library binding.

https://github.com/pharo-rdbms/Pharo-MySQL

Pierce

Sven Van Caekenberghe-2

Re: UFFI Problem: A call to an external function failed (FFIOpaqueObject)

> On 22 Jun 2020, at 03:47, Pierce Ng <[hidden email]> wrote:
>
> Finally, there is a non FFI pure Smalltalk implementation of the MySQL
> wire protocol that has been around a while.

> https://github.com/pharo-rdbms/Pharo-MySQL

Hmm, that is interesting, I somehow missed that.

A little bit more documentation, like a description in the README file would be great though.

Sven

Pierce Ng-3

Re: UFFI Problem: A call to an external function failed (FFIOpaqueObject)

On Mon, Jun 22, 2020 at 08:41:22AM +0200, Sven Van Caekenberghe wrote:
> > On 22 Jun 2020, at 03:47, Pierce Ng <[hidden email]> wrote:
> > Finally, there is a non FFI pure Smalltalk implementation of the MySQL
> > wire protocol that has been around a while.
>
> > https://github.com/pharo-rdbms/Pharo-MySQL
>
> Hmm, that is interesting, I somehow missed that.
> A little bit more documentation, like a description in the README file would be great though.

Agree. Your docu for P3 is the standard to aim for.

Quick bit of history: This driver is the one from Squeaksource that was
then incorporated into DBXTalk and Garage, and finally moved to the GH
repo mentioned above.

http://www.squeaksource.com/StdbMysqlProtocol.html

Pierce

Sven Van Caekenberghe-2

Re: UFFI Problem: A call to an external function failed (FFIOpaqueObject)

Hi Pierce,

> On 23 Jun 2020, at 11:51, Pierce Ng <[hidden email]> wrote:
>
> On Mon, Jun 22, 2020 at 08:41:22AM +0200, Sven Van Caekenberghe wrote:
>>> On 22 Jun 2020, at 03:47, Pierce Ng <[hidden email]> wrote:
>>> Finally, there is a non FFI pure Smalltalk implementation of the MySQL
>>> wire protocol that has been around a while.
>>
>>> https://github.com/pharo-rdbms/Pharo-MySQL
>>
>> Hmm, that is interesting, I somehow missed that.
>> A little bit more documentation, like a description in the README file would be great though.
>
> Agree. Your docu for P3 is the standard to aim for.

Thanks, but I still do not consider P3 completely documented, though as far as a README in GitHub goes it is quite good.

> Quick bit of history: This driver is the one from Squeaksource that was
> then incorporated into DBXTalk and Garage, and finally moved to the GH
> repo mentioned above.
>
> http://www.squeaksource.com/StdbMysqlProtocol.html

Ah, OK.

Then the origins and original authors should definitively be acknowledged.

> Pierce

Regards,

Sven