自带 getch 函数的隐式转换警告

Question

我找到了 conio.h 的 getch() 的 c 实现。可悲的是，它编译时带有一个转换警告，我不知道我应该怎么做才能正确解决它。我找到了 this link，但我不知道如何实现它。

#include<termios.h>
#include<unistd.h>
#include<stdio.h>
#include"getch.h"

/* reads from keypress, doesn't echo */
int getch(void)
{
    struct termios oldattr, newattr;
    int ch;
    tcgetattr( STDIN_FILENO, &oldattr );
    newattr = oldattr;
    newattr.c_lflag &= ~( ICANON | ECHO );
    tcsetattr( STDIN_FILENO, TCSANOW, &newattr );
    ch = getchar();
    tcsetattr( STDIN_FILENO, TCSANOW, &oldattr );
    return ch;
}

/* reads from keypress, echoes */
int getche(void)
{
    struct termios oldattr, newattr;
    int ch;
    tcgetattr( STDIN_FILENO, &oldattr );
    newattr = oldattr;
    newattr.c_lflag &= ~( ICANON );
    tcsetattr( STDIN_FILENO, TCSANOW, &newattr );
    ch = getchar();
    tcsetattr( STDIN_FILENO, TCSANOW, &oldattr );
    return ch;
}

CLANG 3.5 returns:

getch.c:13:24: warning: implicit conversion changes signedness: 'int' to 'unsigned int' [-Wsign-conversion]
    newattr.c_lflag &= ~( ICANON | ECHO );
                    ~~ ^~~~~~~~~~~~~~~~~~
getch.c:27:24: warning: implicit conversion changes signedness: 'int' to 'unsigned int' [-Wsign-conversion]
    newattr.c_lflag &= ~( ICANON );
                    ~~ ^~~~~~~~~~~
2 warnings generated.

Answer 1

由于整数提升，这些定义被提升为 int，但 c_lflag 成员是无符号整数。

确保按位运算以无符号类型完成：

 newattr.c_lflag &= ~( 0u | ICANON | ECHO );
                        ^

自带 getch 函数的隐式转换警告

Implicit conversion warning with own getch function

c

types

int

unsigned

signed