Re: [Plplot-devel] New way of getting device info from dyndrivers

[<jc...@fe...>]

On Wednesday 05 February 2003 13:55, Rafael Laboissiere wrote:
| * Rafael Laboissiere <lab...@ps...> [2003-02-04 22:37]:
| >    c) At build time (not configuration time), a small C program
| > dlopen the <driver>.c files, get the symbols described above and
| > write the associated device entries in <driver>.rc (or whichever
| > name).
|
| Just to make things a bit more concrete, here is the design that I
| have in mind.  I will take the ps.c driver as an example.  The
| following global variables will be defined in the driver source:
|
|     char* DEVICES_ps      =3D "ps:psc";
|
|     char* DESCRIPTION_ps  =3D "PostScript File (monochrome)";
|     int   TYPE_ps         =3D plDevType_FileOriented;
|     int   SEQNUM_ps       =3D 29;
|     char* SYMTAG_ps       =3D "psm";
|
|     char* DESCRIPTION_psc =3D "PostScript File (color)";
|     int   TYPE_psc        =3D plDevType_FileOriented;
|     int   SEQNUM_psc      =3D 30;
|     char* SYMTAG_psc      =3D "psc";
|
| Of course, these variables should be used in the plD_dispatch_init_*
| functions.  In the case of ps.c:
|
|     ps_dispatch_init_helper( pdt,
|                              DESCRIPTION_ps, "ps",
|                              TYPE_ps, SEQNUM_ps,
|                              (plD_init_fp) plD_init_psm );
|
|     ps_dispatch_init_helper( pdt,
|                              DESCRIPTION_psc, "psc",
|                              TYPE_psc, SEQNUM_psc,
|                              (plD_init_fp) plD_init_psc );
|
| This will insure that things are not defined twice in different
| places (like with the current DEVICE_INFO_* variable).
|
| The small C program that will generate the <driver>.rc file from the
| <driver>.la file, would do: (1) dlopen the module; (2) get the
| DEVICES_* symbol and parse its device components (in the ps.c
| exemple, that would be "ps" and "psc"); (3) for each one of the
| devices found, get the symbols DESCRIPTION_<dev>, TYPE_<dev>,
| SEQNUM_<dev>, and SYMTAG_<dev>; (4) create the temp file that is
| parsed by Geoff's code. (This could be improved along Joao's
| suggestion of creating a structure instead of writing the information
| in a temp file.)
|
| We have to decide first whether it is not worth abandoning the
| current approach and adopting this "cached info" approach above.=20

I decided to give it a try but got a seg fault:

[jcard@feup] gdb x01c
(gdb) run -dev xwin
Starting program: /usr/local/test/lib/plplot5.2.0/examples/c/x01c -dev=20
xwin

Program received signal SIGSEGV, Segmentation fault.
0x0806a46e in lt_dlsym (handle=3D0x807b0e0,=20
    symbol=3D0xbfffef50 "DEVICE_INFO_pstex") at ltdl.c:3330
3330      lensym =3D LT_STRLEN (symbol) + LT_STRLEN=20
(handle->loader->sym_prefix)
(gdb) where
#0  0x0806a46e in lt_dlsym (handle=3D0x807b0e0,=20
    symbol=3D0xbfffef50 "DEVICE_INFO_pstex") at ltdl.c:3330
#1  0x08053d38 in plInitDispatchTable () at plcore.c:1638
#2  0x08049b9d in plMergeOpts (options=3D0x8073500,=20
    name=3D0x11 <Address 0x11 out of bounds>, notes=3D0x11) at plargs.c:6=
99
#3  0x08049362 in main ()
#4  0x400674a2 in __libc_start_main () from /lib/libc.so.6


| There is also Joao's suggestion for dynamically building the
| drivers.db, but I am too lazy to implement that (and I am not sure it
| is a superior approach).
|
| What do you think?  I accept suggestions for better variable names.