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Thread: Extending PostgreSQL Using C

Extending PostgreSQL Using C

From
Boulat Khakimov
Date:
Hi,

Im writing a C function for PG to do one way encryption using crypt.
Here is the source code

#include <ctype.h>
#include <unistd.h>
#include "postgres.h"
#include "utils/builtins.h"

text *encrypt(text *string){
        text       *ret;
        int                     m;

        if ((string == (text *) NULL) || ((m = VARSIZE(string) -
VARHDRSZ) <= 0))
                return string;

        ret = (text *) palloc(20);


        ret = (text *) crypt(string,"AB");

        return ret;

}


then I compile it like so:


gcc -I/usr/src/postgresql-7.0.3/src/include \
    -I/usr/src/postgresql-7.0.3/src/backend   -O2 -Wall
-Wmissing-prototypes  \
    -Wmissing-declarations \
    -I/usr/src/postgresql-7.0.3/src/interfaces/libpq \
    -I/usr/src/postgresql-7.0.3/src/include -fpic   -c -o encrypt.o
encrypt.c

gcc -shared -o encrypt.so  encrypt.o

rm encrypt.o

then in PG, I do the following

test=> CREATE FUNCTION encrypt(text)
test->RETURNS text
test->AS '/[full path here]/encrypt.so'
test->LANGUAGE 'C';
CREATE

Now when I try
test=> SELECT encrypt('Blah');
it gives me this error

ERROR:  Can't find function encrypt in file /[full path here]/encrypt.so


Why do I get this error????
Any ideas?


Regards,
Boulat Khakimov



--
Nothing Like the Sun

Re: [DOCS] Extending PostgreSQL Using C

From
Tom Lane
Date:
Boulat Khakimov <boulat@inet-interactif.com> writes:
> ERROR:  Can't find function encrypt in file /[full path here]/encrypt.so
> Why do I get this error????

Offhand I see nothing wrong with your procedure.  Try running 'nm' on
the .so file to see what symbols it says the .so defines.

What platform is this on, anyway?

            regards, tom lane

Re: [DOCS] Extending PostgreSQL Using C

From
Boulat Khakimov
Date:
Tom Lane wrote:
>
> Boulat Khakimov <boulat@inet-interactif.com> writes:
> > ERROR:  Can't find function encrypt in file /[full path here]/encrypt.so
> > Why do I get this error????
>
> Offhand I see nothing wrong with your procedure.  Try running 'nm' on
> the .so file to see what symbols it says the .so defines.
>
> What platform is this on, anyway?


Linux 2.2.18 #23 Tue Feb 6 13:21:15 EST 2001 i686 unknown


Regards,
Boulat


--
Nothing Like the Sun

Re: [DOCS] Extending PostgreSQL Using C

From
Tom Lane
Date:
Hannu Krosing <hannu@tm.ee> writes:
> Boulat Khakimov wrote:
>> ERROR:  Can't find function encrypt in file /[full path here]/encrypt.so

> Can _postgres_ user read /[full path here]/encrypt.so ?

Presumably so.  If he were unable to load the .so file, he'd be getting
a different error message.  This message indicates that he got past the
load step, but dl_sym is unable to resolve the symbol "encrypt".

I asked about the symbol names shown by nm(1), but got no answer ...

            regards, tom lane

Re: [DOCS] Extending PostgreSQL Using C

From
Nishad Prakash
Date:
On Wed, 7 Mar 2001, Tom Lane wrote:

> Hannu Krosing <hannu@tm.ee> writes:
> > Boulat Khakimov wrote:
> >> ERROR:  Can't find function encrypt in file /[full path here]/encrypt.so
>
> > Can _postgres_ user read /[full path here]/encrypt.so ?
>
> Presumably so.  If he were unable to load the .so file, he'd be getting
> a different error message.  This message indicates that he got past the
> load step, but dl_sym is unable to resolve the symbol "encrypt".
>
> I asked about the symbol names shown by nm(1), but got no answer ...

It should be noted that encrypt() is a function already declared in
unistd.h, which the OP is including.  Could that be causing some problem
since the OP is using the same name?

Nishad
--
"Underneath the concrete, the dream is still alive" -- Talking Heads

Re: [DOCS] Extending PostgreSQL Using C

From
Hannu Krosing
Date:
Boulat Khakimov wrote:

> Hi,
>
> Im writing a C function for PG to do one way encryption using crypt.
> Here is the source code
>
> it gives me this error
>
> ERROR:  Can't find function encrypt in file /[full path here]/encrypt.so
>
>
> Why do I get this error????
> Any ideas?

Can _postgres_ user read /[full path here]/encrypt.so ?

---------------
Hannu