dl_dlopen.xs revision 7c478bd95313f5f23a4c958a745db2134aa03244
/* dl_dlopen.xs
*
* Author: Paul Marquess (Paul.Marquess@btinternet.com)
* Created: 10th July 1994
*
* Modified:
* 15th July 1994 - Added code to explicitly save any error messages.
* 3rd August 1994 - Upgraded to v3 spec.
* 9th August 1994 - Changed to use IV
* 10th August 1994 - Tim Bunce: Added RTLD_LAZY, switchable debugging,
* basic FreeBSD support, removed ClearError
* 29th Feburary 2000 - Alan Burlison: Added functionality to close dlopen'd
* files when the interpreter exits
*
*/
/* Porting notes:
Definition of Sunos dynamic Linking functions
=============================================
In order to make this implementation easier to understand here is a
quick definition of the SunOS Dynamic Linking functions which are
used here.
dlopen
------
void *
dlopen(path, mode)
char * path;
int mode;
This function takes the name of a dynamic object file and returns
a descriptor which can be used by dlsym later. It returns NULL on
error.
The mode parameter must be set to 1 for Solaris 1 and to
RTLD_LAZY (==2) on Solaris 2.
dlclose
-------
int
dlclose(handle)
void * handle;
This function takes the handle returned by a previous invocation of
dlopen and closes the associated dynamic object file. It returns zero
on success, and non-zero on failure.
dlsym
------
void *
dlsym(handle, symbol)
void * handle;
char * symbol;
Takes the handle returned from dlopen and the name of a symbol to
get the address of. If the symbol was found a pointer is
returned. It returns NULL on error. If DL_PREPEND_UNDERSCORE is
defined an underscore will be added to the start of symbol. This
is required on some platforms (freebsd).
dlerror
------
char * dlerror()
Returns a null-terminated string which describes the last error
that occurred with either dlopen or dlsym. After each call to
dlerror the error message will be reset to a null pointer. The
SaveError function is used to save the error as soon as it happens.
Return Types
============
In this implementation the two functions, dl_load_file &
dl_find_symbol, return void *. This is because the underlying SunOS
dynamic linker calls also return void *. This is not necessarily
the case for all architectures. For example, some implementation
will want to return a char * for dl_load_file.
If void * is not appropriate for your architecture, you will have to
change the void * to whatever you require. If you are not certain of
how Perl handles C data types, I suggest you start by consulting
Dean Roerich's Perl 5 API document. Also, have a look in the typemap
file (in the ext directory) for a fairly comprehensive list of types
that are already supported. If you are completely stuck, I suggest you
post a message to perl5-porters, comp.lang.perl.misc or if you are really
desperate to me.
Remember when you are making any changes that the return value from
dl_load_file is used as a parameter in the dl_find_symbol
function. Also the return value from find_symbol is used as a parameter
to install_xsub.
Dealing with Error Messages
============================
In order to make the handling of dynamic linking errors as generic as
possible you should store any error messages associated with your
implementation with the StoreError function.
In the case of SunOS the function dlerror returns the error message
associated with the last dynamic link error. As the SunOS dynamic
linker functions dlopen & dlsym both return NULL on error every call
to a SunOS dynamic link routine is coded like this
RETVAL = dlopen(filename, 1) ;
if (RETVAL == NULL)
SaveError("%s",dlerror()) ;
Note that SaveError() takes a printf format string. Use a "%s" as
the first parameter if the error may contain any % characters.
*/
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#ifdef I_DLFCN
#else
#include <nlist.h>
#include <link.h>
#endif
#ifndef RTLD_LAZY
#endif
#ifndef HAS_DLERROR
# ifdef __NetBSD__
# else
# define dlerror() "Unknown error - dlerror() not implemented"
# endif
#endif
#include "dlutils.c" /* SaveError() etc */
static void
{
(void)dl_generic_private_init(aTHX);
}
BOOT:
(void)dl_private_init(aTHX);
void
char * filename
int flags
void *handle;
CODE:
{
#if defined(DLOPEN_WONT_DO_RELATIVE_PATHS)
}
}
#endif
#ifdef RTLD_NOW
{
if (dl_nonlazy)
}
#endif
if (flags & 0x01)
#ifdef RTLD_GLOBAL
mode |= RTLD_GLOBAL;
#else
#endif
ST(0) = sv_newmortal() ;
else
}
int
void * libref
CODE:
if (!RETVAL)
void
void * libhandle
char * symbolname
void *sym;
CODE:
#ifdef DLSYM_NEEDS_UNDERSCORE
#endif
"dl_find_symbol(handle=%lx, symbol=%s)\n",
(unsigned long) libhandle, symbolname));
" symbolref = %lx\n", (unsigned long) sym));
ST(0) = sv_newmortal() ;
else
void
CODE:
void
char * perl_name
void * symref
char * filename
CODE:
filename)));
char *
dl_error()
CODE:
RETVAL = dl_last_error ;
# end.