problem using rebar to compile c source - c

Question

I tried to use rebar to compile an iconv port extracted from ejabberd (http://www.ejabberd.im/), it successfully generated an "iconv_erl.so".
but when I use erl_ddll:load_driver("priv/", iconv_erl)
to load it, it returns {error,{open_error,-10}}.
Is there anything I am missing? thx in advance.
p.s. The c source is as follows:
/*
* ejabberd, Copyright (C) 2002-2010 ProcessOne
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
* 02111-1307 USA
*
*/
#include <stdio.h>
#include <string.h>
#include <erl_driver.h>
#include <ei.h>
#include <iconv.h>
typedef struct {
ErlDrvPort port;
iconv_t cd;
} iconv_data;
static ErlDrvData iconv_erl_start(ErlDrvPort port, char *buff)
{
iconv_data* d = (iconv_data*)driver_alloc(sizeof(iconv_data));
d->port = port;
d->cd = NULL;
set_port_control_flags(port, PORT_CONTROL_FLAG_BINARY);
return (ErlDrvData)d;
}
static void iconv_erl_stop(ErlDrvData handle)
{
driver_free((char*)handle);
}
static int iconv_erl_control(ErlDrvData drv_data,
unsigned int command,
char *buf, int len,
char **rbuf, int rlen)
{
int i;
int size;
int index = 0;
int avail;
size_t inleft, outleft;
ErlDrvBinary *b;
char *from, *to, *string, *stmp, *rstring, *rtmp;
iconv_t cd;
int invalid_utf8_as_latin1 = 0;
ei_decode_version(buf, &index, &i);
ei_decode_tuple_header(buf, &index, &i);
ei_get_type(buf, &index, &i, &size);
from = driver_alloc(size + 1);
ei_decode_string(buf, &index, from);
ei_get_type(buf, &index, &i, &size);
to = driver_alloc(size + 1);
ei_decode_string(buf, &index, to);
ei_get_type(buf, &index, &i, &size);
stmp = string = driver_alloc(size + 1);
ei_decode_string(buf, &index, string);
/* Special mode: parse as UTF-8 if possible; otherwise assume it's
Latin-1. Makes no difference when encoding. */
if (strcmp(from, "utf-8+latin-1") == 0) {
from[5] = '\0';
invalid_utf8_as_latin1 = 1;
}
if (strcmp(to, "utf-8+latin-1") == 0) {
to[5] = '\0';
}
cd = iconv_open(to, from);
if (cd == (iconv_t) -1) {
cd = iconv_open("ascii", "ascii");
if (cd == (iconv_t) -1) {
*rbuf = (char*)(b = driver_alloc_binary(size));
memcpy(b->orig_bytes, string, size);
driver_free(from);
driver_free(to);
driver_free(string);
return size;
}
}
outleft = avail = 4*size;
inleft = size;
rtmp = rstring = driver_alloc(avail);
while (inleft > 0) {
if (iconv(cd, &stmp, &inleft, &rtmp, &outleft) == (size_t) -1) {
if (invalid_utf8_as_latin1 && (*stmp & 0x80) && outleft >= 2) {
/* Encode one byte of (assumed) Latin-1 into two bytes of UTF-8 */
*rtmp++ = 0xc0 | ((*stmp & 0xc0) >> 6);
*rtmp++ = 0x80 | (*stmp & 0x3f);
outleft -= 2;
}
stmp++;
inleft--;
}
}
size = rtmp - rstring;
*rbuf = (char*)(b = driver_alloc_binary(size));
memcpy(b->orig_bytes, rstring, size);
driver_free(from);
driver_free(to);
driver_free(string);
driver_free(rstring);
iconv_close(cd);
return size;
}
ErlDrvEntry iconv_driver_entry = {
NULL, /* F_PTR init, N/A */
iconv_erl_start, /* L_PTR start, called when port is opened */
iconv_erl_stop, /* F_PTR stop, called when port is closed */
NULL, /* F_PTR output, called when erlang has sent */
NULL, /* F_PTR ready_input, called when input descriptor ready */
NULL, /* F_PTR ready_output, called when output descriptor ready */
"iconv_erl", /* char *driver_name, the argument to open_port */
NULL, /* F_PTR finish, called when unloaded */
NULL, /* handle */
iconv_erl_control, /* F_PTR control, port_command callback */
NULL, /* F_PTR timeout, reserved */
NULL /* F_PTR outputv, reserved */
};
DRIVER_INIT(iconv_erl) /* must match name in driver_entry */
{
return &iconv_driver_entry;
}

Answer 1

When you get an error from erl_ddll:load_driver/2, try passing the error to the erl_ddll:format_error/1 function to get more details. For example, I'm currently seeing the same error you are — {open_error, -10} — so I pass that to erl_ddll:format_error/1 in an Erlang shell, as shown below:
1> erl_ddll:format_error({open_error,-10}).
"undefined symbol: _ZTVN10__cxxabiv117__class_type_infoE"
The output shows that my driver won't load because it has an undefined symbol.