[Plplot-devel] Quick help needed with changing a struct and a typedef in PLplot

[Alan W. I. <ir...@be...>]

I start with the background information that is required on the dlopen to
libltdl API change, then get to my two "simple" numbered questions at the
end which any C expert should be able to answer for me.

For the AT branch I am in the middle of changing from the dlopen API
to the libltdl API to increase cross-platform compatibility.

The old API:

void * dlopen (const char *filename, int flag)
void * dlsym (void *handle, char *name)
int dlclose (void *handle)
const char * dlerror (void)

The new API:

lt_dlhandle lt_dlopen (const char *filename)
lt_dlhandle lt_dlopenext (const char *filename)
lt_ptr_t lt_dlsym (lt_dlhandle handle, const char *name)
int lt_dlclose (lt_dlhandle handle)
const char * lt_dlerror (void)

Note: lt_dlopenext is the same as lt_dlopen except that it tries with
alternate suffixes if there is not an exact match to the name.

In the new plcore.c there is the following line:

driver->dlhand = lt_dlopenext( drvspec);

which replaces the old

driver->dlhand = dlopen( drvspec, flag);

Subsequently driver->dlhand is used as an argument to lt_dlsym


So in plplot.h I have changed from

typedef struct {
    char *drvnam;
    void *dlhand;

} PLLoadableDriver;

to

typedef struct {
    char *drvnam;
    lt_dlhandle dlhand;

} PLLoadableDriver;

With appropriate #include of the libltdl header and protection by
#ifdef ENABLE_DYNDRIVERS.

(1) Is that change to the struct the correct thing to do for the changed API?

(2) The new plcore.c code also has the following fragment:

PLDispatchInit dispatch_init = lt_dlsym( driver->dlhand, sym );

where the old disptab.h has

typedef void (*PLDispatchInit)( PLDispatchTable *pdt );

What should I change that typedef to?

My guess is something like

typedef lt_ptr_t (PLDispatchInit)( PLDispatchTable *pdt );

but I am not completely sure so any quick help would be much appreciated.
Of course I am going to try some variations on this theme this afternoon
and hopefully get something to work, but the definitive answer would be
most useful. C typedefs and pointers just plain drive me crazy!

Alan

email: ir...@be...
phone: 250-727-2902	FAX: 250-721-7715
snail-mail:
Dr. Alan W. Irwin
Department of Physics and Astronomy,
University of Victoria, P.O. Box 3055,
Victoria, British Columbia, Canada, V8W 3P6
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