/*-------------------------------------------------------------------------
 *
 * linux.c
 *	  Dynamic Loader for Postgres for Linux, generated from those for
 *	  Ultrix.
 *
 *	  You need to install the dld library on your Linux system!
 *
 * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/port/dynloader/linux.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#ifdef HAVE_DLD_H
#include <dld.h>
#endif

#include "dynloader.h"
#include "miscadmin.h"


#ifndef HAVE_DLOPEN

void *
pg_dlopen(const char *filename)
{
#ifndef HAVE_DLD_H
	elog(ERROR, "dynamic load not supported");
	return NULL;
#else
	static int	dl_initialized = 0;

	/*
	 * initializes the dynamic loader with the executable's pathname. (only
	 * needs to do this the first time pg_dlopen is called.)
	 */
	if (!dl_initialized)
	{
		if (dld_init(dld_find_executable(my_exec_path)))
			return NULL;

		/*
		 * if there are undefined symbols, we want dl to search from the
		 * following libraries also.
		 */
		dl_initialized = 1;
	}

	/*
	 * link the file, then check for undefined symbols!
	 */
	if (dld_link(filename))
		return NULL;

	/*
	 * If undefined symbols: try to link with the C and math libraries! This
	 * could be smarter, if the dynamic linker was able to handle shared libs!
	 */
	if (dld_undefined_sym_count > 0)
	{
		if (dld_link("/usr/lib/libc.a"))
		{
			elog(WARNING, "could not link C library");
			return NULL;
		}
		if (dld_undefined_sym_count > 0)
		{
			if (dld_link("/usr/lib/libm.a"))
			{
				elog(WARNING, "could not link math library");
				return NULL;
			}
			if (dld_undefined_sym_count > 0)
			{
				int			count = dld_undefined_sym_count;
				char	  **list = dld_list_undefined_sym();

				/* list the undefined symbols, if any */
				do
				{
					elog(WARNING, "\"%s\" is undefined", *list);
					list++;
					count--;
				} while (count > 0);

				dld_unlink_by_file(filename, 1);
				return NULL;
			}
		}
	}

	return (void *) strdup(filename);
#endif
}

PGFunction
pg_dlsym(void *handle, const char *funcname)
{
#ifndef HAVE_DLD_H
	return NULL;
#else
	return (PGFunction) dld_get_func((funcname));
#endif
}

void
pg_dlclose(void *handle)
{
#ifndef HAVE_DLD_H
#else
	dld_unlink_by_file(handle, 1);
	free(handle);
#endif
}

char *
pg_dlerror(void)
{
#ifndef HAVE_DLD_H
	return "dynaloader unsupported";
#else
	return dld_strerror(dld_errno);
#endif
}

#endif							/* !HAVE_DLOPEN */
