Onde estão as definições para as declarações de protótipo em bsd / stdlib.h?

Question

Eu tenho um programa em C no Ubuntu 16.04, no qual eu gostaria de usar arc4random_uniform .

typedef unsigned char u_char;
#include <bsd/stdlib.h>
int main () { return (int) arc4random_uniform(100); }

Espero que isso retorne ao sistema operacional com um código de saída aleatória entre 0 e 100. Compilando:

$ gcc -o rand_test ./rand_test.c -lbsd 
/tmp/ccGL6qmU.o: In function 'main':
:(.text+0xa): undefined reference to 'arc4random_uniform'
collect2: error: ld returned 1 exit status

Pacote libbsd-dev fornece /usr/include/bsd/stdlib.h . Este arquivo se parece com:

/*
 * Copyright © 2005 Aurelien Jarno
 * Copyright © 2006 Robert Millan
 * Copyright © 2008-2011 Guillem Jover <[email protected]>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifdef LIBBSD_OVERLAY
#include_next <stdlib.h>
#else
#include <stdlib.h>
#endif

/* For compatibility with NetBSD, which defines humanize_number here. */
#ifdef LIBBSD_OVERLAY
#include <libutil.h>
#else
#include <bsd/libutil.h>
#endif

#ifndef LIBBSD_STDLIB_H
#define LIBBSD_STDLIB_H

#include <sys/cdefs.h>
#include <sys/stat.h>
#include <stdint.h>

__BEGIN_DECLS
uint32_t arc4random(void);
void arc4random_stir(void);
void arc4random_addrandom(u_char *dat, int datlen);
void arc4random_buf(void *_buf, size_t n);
uint32_t arc4random_uniform(uint32_t upper_bound);

int dehumanize_number(const char *str, int64_t *size);

const char *getprogname(void);
void setprogname(const char *);

int heapsort (void *, size_t, size_t, int (*)(const void *, const void *));
int mergesort(void *base, size_t nmemb, size_t size,
              int (*cmp)(const void *, const void *));
int radixsort(const unsigned char **base, int nmemb,
              const unsigned char *table, unsigned endbyte);
int sradixsort(const unsigned char **base, int nmemb,
               const unsigned char *table, unsigned endbyte);

void *reallocf(void *ptr, size_t size);
void *reallocarray(void *ptr, size_t nmemb, size_t size);

long long strtonum(const char *nptr, long long minval, long long maxval,
                   const char **errstr);

char *getbsize(int *headerlenp, long *blocksizep);
__END_DECLS

#endif

Ele contém declarações, mas nenhuma função real. pkg-config --libs libbsd imprime -lbsd (que eu já compilei).

Os seguintes pacotes estão instalados:

libbsd-dev/xenial,now 0.8.2-1 amd64 [installed]
  utility functions from BSD systems - development files

libbsd0/xenial,now 0.8.2-1 amd64 [installed]
  utility functions from BSD systems - shared library

man 3 arc4random_uniform diz:

LIBRARY
    Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS
    #include <bsd/stdlib.h>

Isso certamente parece que #include <bsd/stdlib.h> e gcc ... -lbsd devem funcionar, mas isso não acontece.

Posso usar arc4random_uniform e amigos no Linux? Qual cabeçalho devo incluir ou pacote devo instalar para encontrar as declarações dessas funções?

Aqui está o resultado dos comandos sugeridos nos comentários:

cat @ mint-kitty : ~/projects/c/junk $ cat > rand_test.c
typedef unsigned char u_char;
#include <bsd/stdlib.h>
int main () { return (int) arc4random_uniform(100); }

cat @ mint-kitty : ~/projects/c/junk $ gcc -o rand_test ./rand_test.c -Wl,--verbose -lbsd | grep bsd
attempt to open /usr/lib/gcc/x86_64-linux-gnu/5/libbsd.so failed
attempt to open /usr/lib/gcc/x86_64-linux-gnu/5/libbsd.a failed
attempt to open /usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libbsd.so succeeded
-lbsd (/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libbsd.so)

cat @ mint-kitty : ~/projects/c/junk $ ls -l /lib/x86_64-linux-gnu/libbsd*
lrwxrwxrwx 1 root root    15 Jan 28 00:11 /lib/x86_64-linux-gnu/libbsd.so.0 -> libbsd.so.0.8.2
-rw-r--r-- 1 root root 81040 Jan 28 00:11 /lib/x86_64-linux-gnu/libbsd.so.0.8.2