dynloader and PLs [was: plperl intial pass]

Jan Wieck wrote:
>
> Mark Hollomon wrote:
>
> > Jan Wieck wrote:
> > >
> > > A dynamically loadable Tcl module contains one special
> > > function named <libname>_Init() where first character of
> > > libname is capitalized. On dynamic load, this function is
> > > called with the invoking interpreter as argument. This
> > > function then calls Tcl_CreateCommand() etc. to tell Tcl
> > ^^^^^^^^^^^^^^^^^
> >
> > And here-in lies the problem. Tcl_CreateCommand is sitting, not
> > in the executable, but in the shared-lib with the function call
> > handler. dlopen(), by default will not link across shared-libs.
> >
> > postgres
> > /-----/ \-----\
> > | |
> > plperl.so ---> Opcode.so
> > ^^
> > This link doesn't happen.
>
> But it does for PL/Tcl - at least under Linux-ELF. (C = Call
> to, L = Location of functions code segment):
>
> +-------------------------+
> | postgres |
> +-------------------------+
> |
> | dynamic load
> |
> v
> +---------------------------+ +---------------------------+
> | pltcl.so |--------->| libtcl8.0.so |
> | | auto- | |
> | C Tcl_CreateInterp() | dynamic | L Tcl_CreateInterp() |
> | C Tcl_CreateCommand() | load | L Tcl_CreateCommand() |
> | L static pltcl_SPI_exec() | | C pltcl_SPI_exec() |
> +---------------------------+ +---------------------------+
>
> After loading of pltcl.so, it calls Tcl_CreateInterp() to
> build a Tcl interpreter, and then calls Tcl_CreateCommand()
> to tell that interpreter the address of one of it's hidden
> (static) functions plus a name for it from the script side.
> The interpreter just remembers this in it's command hash
> table, and if that keyword occurs when it expects a
> command/procedure name, just calls it via the function
> pointer.

AHHH, now I understand the difference. By default, the perl installation
does not create a shared library. It creates a static archive only.
And the three linux distros that I have experience with don't force
the creation of the shared lib. So, my situation is:

postgres
|
|
+----------------------+ +-----------------+
| plperl.so | | Opcode.so |
| +--------------+ | | |
| | libperl.a | <-+------------| |
| +--------------+ | | |
+----------------------+ +-----------------+

And it is THAT link that I cannot get to happen without the RTLD_GLOBAL
flag I mentioned.

Sorry for the confusion.

Hopefully you can help find a way out of this.

I had a patch to change the way dynloader worked on linuxelf,
but over night my disk crashed. brand new UDMA/66 drive. Grrrr.

--

Mark Hollomon
mhh(at)nortelnetworks(dot)com
ESN 451-9008 (302)454-9008