取消引用指向不完整类型tcphdr->成员的指针

Question

我使用套接字捕获tcp数据，但构建失败。我的环境是visual studio 2017。我得到错误输出：

 1>/root/projects/frame_capture/framecapture.c:199:60:error : dereferencing pointer to incomplete type
 1>  int header_size = sizeof(struct ethhdr) + iphdrlen + (tcph->doff) * 4;

另外，visual studio 2017命令行是：

"gcc" -W"switch" -W"no-deprecated-declarations" -W"empty-body" -W"conversion" -W"return-type" -W"parentheses" -W"no-pointer-sign" -W"no-format" -W"uninitialized" -W"unreachable-code" -W"unused-function" -W"unused-value" -W"unused-variable" -std=c++14 -x c -Wall -fno-strict-aliasing -g2 -gdwarf-2 "g++" -O0 "3600000" -fthreadsafe-statics -W"switch" -W"no-deprecated-declarations" -W"empty-body" -W"conversion" -W"return-type" -W"parentheses" -W"no-format" -W"uninitialized" -W"unreachable-code" -W"unused-function" -W"unused-value" -W"unused-variable" -frtti -fno-omit-frame-pointer -std=c11 -fexceptions -o "D:\linuxCproject\frame_capture\frame_capture\obj\x64\Debug\%(filename).o" 

我在linux上用gcc构建的，一切都成功了。linux代码：

[root@localhost netinet]# gcc -o o.out framecapture.c

我想知道如何在visual studio中解决这个问题。代码行：

unsigned short iphdrlen;

struct iphdr *iph = (struct iphdr *)(Buffer + sizeof(struct ethhdr));
iphdrlen = iph->ihl * 4;

struct tcphdr *tcph = (struct tcphdr*)(Buffer + iphdrlen + sizeof(struct ethhdr));

int header_size = sizeof(struct ethhdr) + iphdrlen + (tcph->doff) * 4;

但是，我像这样包含了.h文件：

#include<netinet/tcp.h>   //Provides declarations for tcp header

tcp.h中的定义如下：

    # else /* !__FAVOR_BSD */
struct tcphdr
  {
    u_int16_t source;
    u_int16_t dest;
    u_int32_t seq;
    u_int32_t ack_seq;
#  if __BYTE_ORDER == __LITTLE_ENDIAN
    u_int16_t res1:4;
    u_int16_t doff:4;
    u_int16_t fin:1;
    u_int16_t syn:1;
    u_int16_t rst:1;
    u_int16_t psh:1;
    u_int16_t ack:1;
    u_int16_t urg:1;
    u_int16_t res2:2;
#  elif __BYTE_ORDER == __BIG_ENDIAN
    u_int16_t doff:4;
    u_int16_t res1:4;
    u_int16_t res2:2;
    u_int16_t urg:1;
    u_int16_t ack:1;
    u_int16_t psh:1;
    u_int16_t rst:1;
    u_int16_t syn:1;
    u_int16_t fin:1;
#  else
#   error "Adjust your <bits/endian.h> defines"
#  endif
    u_int16_t window;
    u_int16_t check;
    u_int16_t urg_ptr;
};
# endif /* __FAVOR_BSD */

Answer 1

最后，我通过自己的探索解决了这个问题。

主要的问题是构建命令。

-> -> C/C++ -> Language -> C语言标准选择了C99/C89等正确的标准，我选择了缺省值，解决了编译问题。将c++语言标准设置为与C相同，我也选择了默认。

在那之后，我得到命令行：

"gcc" -W"switch" -W"no-deprecated-declarations" -W"empty-body" -W"conversion" -W"return-type" -W"parentheses" -W"no-pointer-sign" -W"no-format" -W"uninitialized" -W"unreachable-code" -W"unused-function" -W"unused-value" -W"unused-variable" -Wall -fno-strict-aliasing -g2 -gdwarf-2 "g++" -O0 "3600000" -fthreadsafe-statics -W"switch" -W"no-deprecated-declarations" -W"empty-body" -W"conversion" -W"return-type" -W"parentheses" -W"no-format" -W"uninitialized" -W"unreachable-code" -W"unused-function" -W"unused-value" -W"unused-variable" -frtti -fno-omit-frame-pointer -fexceptions -o "D:\linuxCproject\icmprequest\icmprequest\obj\x64\Debug\%(filename).o" 

提示:在处理!__FAVOR_BSD时，不同的标准是不同的。