当我尝试使用我目前的C语言知识在我的项目中实现LLDP功能时，我遇到了这个问题。编译给出错误说明/home/tiara/NetBeansProjects/CppApplication_2/main.c:212: undefined reference to快照”
生成此代码的代码段是
voidlldp_print(const u_char *p, u_int len)
{
u_int16_t tlv;
u_int8_t *ptr = (u_int8_t *)p, v = 0;
int n, type, vlen, alen;
printf("LLDP");
#define _ptrinc(_v) ptr += (_v); vlen -= (_v);
for (n = 0; n < len;) {
TCHECK2(*ptr, sizeof(tlv)); //HERE IS WHERE THE ERROR POINTS TO
非常感谢您提出的有关纠正此错误的建议，因为我几天来一直试图解决此问题，但没有运气。
再次感谢 ：）
费耶
以下是我包含在代码中的
libraries#include <sys/param.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/if_ether.h>
#include <netinet/ether.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "addrtoname.h"
#include "extract.h"
#include "interface.h"
#include "afnum.h"
编辑
TECHECK2在位于http://ftp.cc.uoc.gr/mirrors/OpenBSD/src/usr.sbin/tcpdump/interface.h的interface.h头文件中定义/* $OpenBSD: interface.h,v 1.62 2014/01/11 04:35:52 lteo Exp $ */
/*
* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
* @(#) $Id: interface.h,v 1.62 2014/01/11 04:35:52 lteo Exp $ (LBL)
*/
#ifndef tcpdump_interface_h
#define tcpdump_interface_h
#include "gnuc.h"
#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif
struct tok {
int v; /* value */
char *s; /* string */
};
extern int aflag; /* translate network and broadcast addresses */
extern int dflag; /* print filter code */
extern int eflag; /* print ethernet header */
extern int fflag; /* don't translate "foreign" IP address */
extern int Iflag; /* include interface in output */
extern int nflag; /* leave addresses as numbers */
extern int Nflag; /* remove domains from printed host names */
extern int oflag; /* OS fingerprint */
extern int qflag; /* quick (shorter) output */
extern int Sflag; /* print raw TCP sequence numbers */
extern int tflag; /* print packet arrival time */
extern int vflag; /* verbose */
extern int xflag; /* print packet in hex */
extern int Xflag; /* print packet in hex/ascii */
extern int packettype; /* as specified by -T */
extern char *device; /* as specified by -i */
#define PT_VAT 1 /* Visual Audio Tool */
#define PT_WB 2 /* distributed White Board */
#define PT_RPC 3 /* Remote Procedure Call */
#define PT_RTP 4 /* Real-Time Applications protocol */
#define PT_RTCP 5 /* Real-Time Applications control protocol */
#define PT_CNFP 6 /* Cisco NetFlow protocol */
#define PT_VRRP 7 /* Virtual Router Redundancy protocol */
#define PT_TCP 8 /* TCP */
#ifndef min
#define min(a,b) ((a)>(b)?(b):(a))
#endif
#ifndef max
#define max(a,b) ((b)>(a)?(b):(a))
#endif
/*
* The default snapshot length. This value allows most printers to print
* useful information while keeping the amount of unwanted data down.
* In particular, it allows ethernet, tcp/ip headers, and a small amount
* of data, or to capture IPv6 and TCP headers after pflog encapsulation.
*/
#define DEFAULT_SNAPLEN 116
#define IEEE802_11_SNAPLEN (DEFAULT_SNAPLEN + 30)
#define IEEE802_11_RADIO_SNAPLEN (IEEE802_11_SNAPLEN + 64)
#ifndef BIG_ENDIAN
#define BIG_ENDIAN 4321
#define LITTLE_ENDIAN 1234
#endif
#ifdef ETHER_HEADER_HAS_EA
#define ESRC(ep) ((ep)->ether_shost.ether_addr_octet)
#define EDST(ep) ((ep)->ether_dhost.ether_addr_octet)
#else
#define ESRC(ep) ((ep)->ether_shost)
#define EDST(ep) ((ep)->ether_dhost)
#endif
#ifdef ETHER_ARP_HAS_X
#define SHA(ap) ((ap)->arp_xsha)
#define THA(ap) ((ap)->arp_xtha)
#define SPA(ap) ((ap)->arp_xspa)
#define TPA(ap) ((ap)->arp_xtpa)
#else
#ifdef ETHER_ARP_HAS_EA
#define SHA(ap) ((ap)->arp_sha.ether_addr_octet)
#define THA(ap) ((ap)->arp_tha.ether_addr_octet)
#else
#define SHA(ap) ((ap)->arp_sha)
#define THA(ap) ((ap)->arp_tha)
#endif
#define SPA(ap) ((ap)->arp_spa)
#define TPA(ap) ((ap)->arp_tpa)
#endif
#ifndef NTOHL
#define NTOHL(x) (x) = ntohl(x)
#define NTOHS(x) (x) = ntohs(x)
#define HTONL(x) (x) = htonl(x)
#define HTONS(x) (x) = htons(x)
#endif
#endif
extern char *program_name; /* used to generate self-identifying messages */
extern int32_t thiszone; /* seconds offset from gmt to local time */
extern int snaplen;
/* global pointers to beginning and end of current packet (during printing) */
extern const u_char *packetp;
extern const u_char *snapend;
/*
* True if "l" bytes of "var" were captured.
*
* The "snapend - (l) <= snapend" checks to make sure "l" isn't so large
* that "snapend - (l)" underflows.
*
* The check is for <= rather than < because "l" might be 0.
*/
#define TTEST2(var, l) (snapend - (l) <= snapend && \
(const u_char *)&(var) <= snapend - (l))
/* True if "var" was captured */
#define TTEST(var) TTEST2(var, sizeof(var))
/* Bail if "l" bytes of "var" were not captured */
#define TCHECK2(var, l) if (!TTEST2(var, l)) goto trunc
/* Bail if "var" was not captured */
#define TCHECK(var) TCHECK2(var, sizeof(var))
struct timeval;
struct bpf_timeval;
extern void ts_print(const struct bpf_timeval *);
extern int fn_print(const u_char *, const u_char *);
extern int fn_printn(const u_char *, u_int, const u_char *);
extern void relts_print(int);
extern const char *tok2str(const struct tok *, const char *, int);
extern char *dnaddr_string(u_short);
extern void safeputs(const char *);
extern void safeputchar(int);
extern void printb(char *, unsigned short, char *);
extern void wrapup(int);
extern __dead void error(const char *, ...)
__attribute__((__format__ (printf, 1, 2)));
extern void warning(const char *, ...)
__attribute__ ((__format__ (printf, 1, 2)));
extern char *read_infile(char *);
extern char *copy_argv(char * const *);
extern char *isonsap_string(const u_char *);
extern char *llcsap_string(u_char);
extern char *protoid_string(const u_char *);
extern char *dnname_string(u_short);
extern char *dnnum_string(u_short);
/* The printer routines. */
struct pcap_pkthdr;
extern int ether_encap_print(u_short, const u_char *, u_int, u_int);
extern int llc_print(const u_char *, u_int, u_int, const u_char *,
const u_char *);
extern int pppoe_if_print(u_short, const u_char *, u_int, u_int);
extern void aarp_print(const u_char *, u_int);
extern void arp_print(const u_char *, u_int, u_int);
extern void atalk_print(const u_char *, u_int);
extern void atalk_print_llap(const u_char *, u_int);
extern void atm_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void bootp_print(const u_char *, u_int, u_short, u_short);
extern void bgp_print(const u_char *, int);
extern void decnet_print(const u_char *, u_int, u_int);
extern void default_print(const u_char *, u_int);
extern void default_print_unaligned(const u_char *, u_int);
extern void dvmrp_print(const u_char *, u_int);
extern void egp_print(const u_char *, u_int, const u_char *);
extern void enc_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void pflog_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void pflog_old_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void pfsync_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void pfsync_ip_print(const u_char *, u_int, const u_char *);
extern void ether_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void fddi_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void ppp_ether_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void gre_print(const u_char *, u_int);
extern void icmp_print(const u_char *, u_int, const u_char *);
extern void ieee802_11_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void ieee802_11_radio_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void iapp_print(const u_char *, u_int);
extern void igrp_print(const u_char *, u_int, const u_char *);
extern void ip_print(const u_char *, u_int);
extern void ipx_print(const u_char *, u_int);
extern void isoclns_print(const u_char *, u_int, u_int, const u_char *,
const u_char *);
extern void krb_print(const u_char *, u_int);
extern void netbeui_print(u_short, const u_char *, const u_char *);
extern void ipx_netbios_print(const u_char *, const u_char *);
extern void nbt_tcp_print(const u_char *, int);
extern void nbt_udp137_print(const u_char *data, int);
extern void nbt_udp138_print(const u_char *data, int);
extern char *smb_errstr(int, int);
extern void print_data(const unsigned char *, int);
extern void l2tp_print(const u_char *dat, u_int length);
extern void vrrp_print(const u_char *bp, u_int len, int ttl);
extern void carp_print(const u_char *bp, u_int len, int ttl);
extern void hsrp_print(const u_char *, u_int);
extern void vqp_print(const u_char *, u_int);
extern void nfsreply_print(const u_char *, u_int, const u_char *);
extern void nfsreq_print(const u_char *, u_int, const u_char *);
extern void ns_print(const u_char *, u_int, int);
extern void ntp_print(const u_char *, u_int);
extern void loop_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void null_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void ospf_print(const u_char *, u_int, const u_char *);
extern void mobile_print(const u_char *, u_int);
extern void pim_print(const u_char *, u_int);
extern void ppp_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void ppp_hdlc_print(const u_char *, int);
extern void raw_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void rip_print(const u_char *, u_int);
extern void sl_if_print(u_char *, const struct pcap_pkthdr *, const u_char *);
extern void sl_bsdos_if_print(u_char *, const struct pcap_pkthdr *,
const u_char *);
extern void snmp_print(const u_char *, u_int);
extern void sunrpcrequest_print(const u_char *, u_int, const u_char *);
extern void cnfp_print(const u_char *, u_int, const u_char *);
extern void tcp_print(const u_char *, u_int, const u_char *);
extern void tftp_print(const u_char *, u_int);
extern void timed_print(const u_char *, u_int);
extern void udp_print(const u_char *, u_int, const u_char *);
extern void wb_print(const void *, u_int);
extern void ike_print(const u_char *, u_int);
extern void udpencap_print(const u_char *, u_int, const u_char *);
extern void ah_print(const u_char *, u_int, const u_char *);
extern void esp_print(const u_char *, u_int, const u_char *);
extern void cdp_print(const u_char *, u_int, u_int, const u_char *,
const u_char *);
extern void stp_print(const u_char *, u_int);
extern void radius_print(const u_char *, u_int);
extern void lwres_print(const u_char *, u_int);
extern void ether_print(const u_char *, u_int);
extern void etherip_print(const u_char *, u_int, u_int, const u_char *);
extern void ipcomp_print(const u_char *, u_int, const u_char *);
extern void mpls_print(const u_char *, u_int);
extern void lldp_print(const u_char *, u_int);
extern void slow_print(const u_char *, u_int);
extern void gtp_print(const u_char *, u_int, u_short, u_short);
#ifdef INET6
extern void ip6_print(const u_char *, int);
extern void ip6_opt_print(const u_char *, int);
extern int hbhopt_print(const u_char *);
extern int dstopt_print(const u_char *);
extern int frag6_print(const u_char *, const u_char *);
extern void icmp6_print(const u_char *, u_int, const u_char *);
extern void ripng_print(const u_char *, int);
extern int rt6_print(const u_char *, const u_char *);
extern void ospf6_print(const u_char *, u_int);
extern void dhcp6_print(const u_char *, u_int, u_short, u_short);
#endif /*INET6*/
extern u_short in_cksum(const u_short *addr, register int len, int csum);
编辑2
通过评论，我可以缩小问题范围。我需要知道的是，为什么在以下情况下会生成错误
Undefined reference to snappedTCHECK2(*ptr, sizeof(tlv));明确地将两个值传递给
TCHECK2方法extern const u_char *snapend;
/*
* True if "l" bytes of "var" were captured.
*
* The "snapend - (l) <= snapend" checks to make sure "l" isn't so large
* that "snapend - (l)" underflows.
*
* The check is for <= rather than < because "l" might be 0.
*/
#define TTEST2(var, l) (snapend - (l) <= snapend && \
(const u_char *)&(var) <= snapend - (l))
/* True if "var" was captured */
#define TTEST(var) TTEST2(var, sizeof(var))
/* Bail if "l" bytes of "var" were not captured */
#define TCHECK2(var, l) if (!TTEST2(var, l)) goto trunc
/* Bail if "var" was not captured */
#define TCHECK(var) TCHECK2(var, sizeof(var))
任何建议将不胜感激:)
最佳答案
snapend在interface.h中声明。您还需要的是snapend的定义。所以要么放（从interface.h复制）
const u_char *snapend;
进入您的项目或指向包含变量snapend的lib的链接（我不知道您是从tcpdump获取头文件还是从tcpdump获取.o文件或库）。
关于c - 未定义对“snapend”的引用，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/21780339/