c++ - 如何修复范围内的字符串声明错误

Question

我正在尝试运行进程间通信程序，但它说字符串未按原样在范围内声明，当我添加 #inlcude 时，我收到一条错误消息:

receiver.cpp:25:35: error: invalid conversion from ‘char*’ to ‘int’ [-fpermissive]
     string temp = to_string(argv[0]);
                             ~~~~~~^
In file included from /usr/include/c++/7/string:52:0,
                 from receiver.cpp:14:
/usr/include/c++/7/bits/basic_string.h:6419:3: note: candidate: std::__cxx11::string std::__cxx11::to_string(unsigned int) <near match>
   to_string(unsigned __val)
   ^~~~~~~~~
receiver.cpp:27:26: error: cannot convert ‘std::__cxx11::string {aka std::__cxx11::basic_string<char>}’ to ‘const char*’ for argument ‘1’ to ‘int atoi(const char*)’
     int msgid = atoi(temp) //Converts message id from string to integer
                          ^
receiver.cpp:45:32: error: ‘some_data’ was not declared in this scope
     if (msgrcv(msgid, (void *)&some_data, BUFSIZ, msg_to_receive, 0) == -1) { //revieces message from message queue
                                ^~~~~~~~~
receiver.cpp:49:29: error: ‘some_data’ was not declared in this scope
     printf("You wrote: %s", some_data.some_text);

这是我的代码:

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.H>
#include <cstring.h>
#include <unist.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <cstdlib>
#inlcude <string>

using namespace std;

struct my_msg_st{
long int my_msg_type;
char some_text[BUFSIZ];
};

int main(int argc, char *argv[0]){
int running =1;
string temp = to_string(argv[0]);
int msgid = atoi(temp);
struct my_msg_st some_data;
long int msg_to_receive = 0;

....

if (strncmp(some_data.some_text, "end", 3) == 0){
    running =0;
}

...
exit(0);
}

期望代码打印出从发件人文件发送的消息

Answer 1

以下是针对您的问题的一些修复:
string temp = to_string(argv[0]);
1. to_string 将数字转换为字符串。 argv[0]是 C 风格的字符串，而不是数字。
2.std::string constructor已有一个版本可从 char * 转换至std::string 。

atoi(temp)
1. atoi 函数采用 char * 类型的参数不是std::string 。您需要使用atoi(temp.c_str())或更喜欢std::ostringstream 。

请查看 char 之间的差异数组(又名 C 风格字符串)和 std::string类型。喜欢使用std::string ，特别是在结构中。

使用前请仔细阅读库函数说明。

另请参阅std::ostringstream 。由于这是 C++，因此更喜欢使用 C++ I/O，例如 std::cout和operator << .