大家好我为分配实现了一个多协议服务器，问题是当我使用一个函数（与TCP一起工作得非常好）和UDP时，它会返回一些奇怪的sizeof（rslt）值 这是打印sizeof（rslt）的结果，
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服务器
#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <netinet/tcp.h>
#include <errno.h>
#define MAXLINE 100
struct equation {
float a;
char c;
float b;
};
struct result {
long double res;
};
int MAX (int a,int b){
if (a>b) return a;
return b;
}
int readn(int fd, void *vptr, size_t n)
{
size_t nleft;
ssize_t nread;
char *ptr;
ptr = vptr;
nleft = n;
while (nleft > 0) {
if ( (nread = read(fd, ptr, nleft)) < 0) {
if (errno == EINTR)
nread = 0; /* and call read() again */
else
return (-1);
} else if (nread == 0)
break; /* EOF */
nleft -= nread;
ptr += nread;
}
return (n - nleft); /* return >= 0 */
}
int writen(int fd, const void *vptr, size_t n)
{
size_t nleft;
ssize_t nwritten;
const char *ptr;
printf ("\nI'm In %Lf\n",n);
ptr = vptr;
nleft = n;
printf ("%Lf NNNNN %Lf SIZE %Lf \n",nleft,n,sizeof(*vptr));
while (nleft > 0) {
printf ("%Lf\n",nleft);
fflush (stdout);
if ( (nwritten = write(fd, ptr, nleft)) <= 0) {
if (nwritten < 0 && errno == EINTR)
nwritten = 0; /* and call write() again */
else
return (-1); /* error */
}
nleft -= nwritten;
ptr += nwritten;
}
printf ("\n 5alawees \n");
// printf ("\n%s\n",vptr);
// ffulsh (stdout);
return (n);
}
void HandleClient(int comm_fd);
void Die (const char * msg)
{
perror(msg);
exit(1);
}
int passiveUDP (short port){
struct sockaddr_in servaddr;
int listen_fd;
if ((listen_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
Die("Falied to create socket");
};
//printf ("%d" ,listen_fd);
memset( &servaddr,0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htons(INADDR_ANY);
servaddr.sin_port = htons(port);
if (bind(listen_fd, (struct sockaddr *) &servaddr, sizeof(servaddr))<0)
{
Die("Failed to bind socket to address");
}
return listen_fd;
}
int passiveTCP (short port){
struct sockaddr_in servaddr;
int listen_fd;
if ((listen_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
Die("Falied to create socket");
};
memset( &servaddr,0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htons(INADDR_ANY);
servaddr.sin_port = htons(port);
if (bind(listen_fd, (struct sockaddr *) &servaddr, sizeof(servaddr))<0)
{
Die("Failed to bind socket to address");
}
if (listen(listen_fd, 10) < 0)
{
Die("Failed to listen on server socket");
}
return listen_fd;
}
int main(int argc, char * argv[])
{
if (argc != 2) {
fprintf(stderr, "USAGE: ./HelloITServer <port>\n");
exit(1);
}
char str[100];
int listen_fd, comm_fd;
int usock = passiveUDP (atoi (argv[1])); /* UDP socket */
int tsock = passiveTCP (atoi (argv[1])); /* TCP master socket */
int nfds;
fd_set rfds; /* readable file descriptors */
struct sockaddr_in fsin; /* the request from address */
nfds = MAX(tsock, usock) + 1;
FD_ZERO(&rfds);
while (1) {
FD_SET(tsock, &rfds);
FD_SET(usock, &rfds);
printf ("HELLO");
if(select(nfds, &rfds, NULL, NULL, NULL) < 0){
printf("select error: %d \n",errno);
exit (1);
}
if(FD_ISSET(tsock, &rfds))
{
/* TCP slave socket */
printf ("Hello TCP");
int ssock;
//int alen = sizeof(fsin);
ssock = accept(tsock, (struct sockaddr *) NULL, NULL);
if(ssock < 0)
Die("accept failed: jkjkjkjkjkj \n");
HandleClient (ssock);
close (ssock);
}
if(FD_ISSET(usock, &rfds))
{
printf ("Hello UDP");
HandleClient (usock);
}
}
}
void HandleClient(int comm_fd)
{
struct equation eq;
struct result rslt;
bzero (&eq,sizeof (eq));
bzero (&rslt, sizeof (rslt));
if ((readn (comm_fd, &eq, sizeof(eq))) == 0){
Die("Failed to receive from client");
}
printf ("\n%Lf %Lf\n",sizeof (struct result),sizeof (rslt));
printf ("reciveed %f %c %f",eq.a,eq.c,eq.b);
switch (eq.c) {
case '+':
rslt.res = eq.a+eq.b;
break;
case '-':
rslt.res = eq.a-eq.b;
break;
case '*':
rslt.res = eq.a*eq.b;
break;
case '/':
rslt.res = eq.a/eq.b;
break;
case '%':
rslt.res = (int)eq.a% (int)eq.b;
break;
default:
break;
}
printf ("\n%Lf\n",sizeof(rslt));
printf ("\n%Lf\n",sizeof(rslt));
printf ("\n%Lf\n",sizeof(rslt));
writen (comm_fd, &rslt, sizeof (rslt));
//close (comm_fd);
}
客户（以防万一你需要它）
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include<unistd.h>
#include <float.h>
#include <errno.h>
struct equation {
float a;
char c;
float b;
};
struct result {
long double res;
};
int readn(int fd, void *vptr, size_t n)
{
size_t nleft;
ssize_t nread;
char *ptr;
ptr = vptr;
nleft = n;
while (nleft > 0) {
if ( (nread = read(fd, ptr, nleft)) < 0) {
if (errno == EINTR)
nread = 0; /* and call read() again */
else
return (-1);
} else if (nread == 0)
break; /* EOF */
nleft -= nread;
ptr += nread;
}
return (n - nleft); /* return >= 0 */
}
int writen(int fd, const void *vptr, size_t n)
{
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr = vptr;
nleft = n;
while (nleft > 0) {
if ( (nwritten = write(fd, ptr, nleft)) <= 0) {
if (nwritten < 0 && errno == EINTR)
nwritten = 0; /* and call write() again */
else
return (-1); /* error */
}
nleft -= nwritten;
ptr += nwritten;
}
return (n);
}
int main(int argc,char *argv[])
{
int sockfd,n;
char sendline[100];
char recvline[100];
struct sockaddr_in servaddr;
if (argc != 3) {
fprintf(stderr, "USAGE: ./HelloClient <server_ip> <port>\n");
exit(1);
}
sockfd=socket(AF_INET,SOCK_DGRAM,0);
bzero(&servaddr,sizeof servaddr);
servaddr.sin_family=AF_INET;
servaddr.sin_port= htons(atoi(argv[2]));
inet_pton(AF_INET,argv[1],&(servaddr.sin_addr));
connect(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr));
struct result rslt;
struct equation eq;
//while(1)
//{
printf ("Accepted values by the program, from %f to %f\n", FLT_MIN, FLT_MAX);
printf ("\n possible operations are addition, substraction, division, multiplication and modulo with operators : +,-,*,/,% respectivly\n");
printf ("\nPlease enter the equation in this form only : \"5.0 + 2.0\" with a single space\n");
scanf ("%f %c %f", &eq.a,&eq.c,&eq.b);
if (eq.c!='+' && eq.c!='-' && eq.c!='*' && eq.c!='/' && eq.c!='%'){
printf ("\n possible operations are addition, substraction, division, multiplication and modulo with operators : +,-,*,/,% respectivly\n");
exit (1);
}
if (eq.c== '%'){
if (!(eq.a == (float) ((int) eq.a) && eq.b == (float) ((int) eq.b))){
printf ("Only integer values are accepted with the % operation, please rerun the program\n");
exit (1);
}
}
//bzero( &eq, sizeof(eq));
bzero( &rslt, sizeof(rslt) );
//fgets(sendline,100,stdin); /*stdin = 0 , for standard input */
writen (sockfd, &eq, sizeof(eq));
readn (sockfd, &rslt, sizeof(rslt));
printf("%Lf\n thank you for using this marvelous calculator!\n",rslt.res);
bzero( &eq, sizeof(eq));
exit (1);
//}
}
答案 0 :(得分：8)
sizeof()返回未指定类型的无符号整数值。
格式规范%Lf需要long double参数。
尝试：
printf ("\n%u\n",(unsigned int) sizeof(rslt));
或者，如果您要打印rslt的内容：
printf ("\n%Lf\n",rslt.res);
请注意，当我使用gcc 4.6.3编译printf("%Lf\n", sizeof(rslt));等代码时，我会收到以下警告（请注意，-Wall没有增强警告等选项必要的话）：
so-test.c:13:33: warning: format ‘%Lf’ expects argument of type ‘long double’, but argument 2 has type ‘long unsigned int’ [-Wformat]
并非所有编译器都如此有用，但如果您使用GCC，则应注意警告。
答案 1 :(得分：6)
问题代码中有几个地方试图将sizeof（）的结果'printf（）'作为'long double'值：
printf ("\n%Lf %Lf\n",sizeof (struct result),sizeof (rslt));
...
printf ("\n%Lf\n",sizeof(rslt));
printf ("\n%Lf\n",sizeof(rslt));
printf ("\n%Lf\n",sizeof(rslt));
使用“％zu”打印'sizeof（）'返回的'size_t'值，而不是使用'％Lf'。
（使用“％zd”打印'ssize_t'值）