将char与“\n”警告进行比较:指针和整数之间的比较

I have the following part of C code:

我有C代码的以下部分:

char c;
int n = 0;
while ( (c = getchar()) != EOF ){
    if (c == "\n"){
        n++;
    }
}

during compilation, compiler tells me

编译期间，编译器告诉我

warning: comparison between pointer and integer [enabled by default]

The thing is that if to substitute "\n" with '\n' there are no warnings at all Can anyone explain me the reason. Another strange thing that I am not using pointers at all.

问题是，如果用'\n'替换'\n'，根本就没有任何警告，谁能给我解释一下原因吗?还有一件奇怪的事，我根本不使用指针。

I am aware of the following questions

我知道以下问题

warning: comparison between pointer and integer [enabled by default] in c
警告:在c中，指针和整型[默认启用]之间的比较
warning: comparison between pointer and integer in C
警告:C中的指针和整数的比较

but in my opinion they are unrelated to my question

但在我看来，它们与我的问题无关

PS. If instead of char c; there will be int c; there will be still warning

PS. If代替char c;有int c;仍然会有警告

2 个解决方案

#1

\n' is called a character literal and is a scalar integer type.

\n'被称为字符文本，是标量整数类型。

"\n" is called a string literal and is an array type. Note that arrays decay to pointers and so that's why you're getting that error.

“\n”被称为字符串文字，是数组类型。注意，数组衰减到指针，这就是为什么你会得到这个错误。

This may help you understand:

这可能有助于你理解:

 // analogous to using '\n'
char c;
int n = 0;
while ( (c = getchar()) != EOF ){
    int comparison_value = 10; // 10 is \n in ascii encoding
    if (c == comparison_value){
        n++;
    }
}

// analogous to using "\n"
char c;
int n = 0;
while ( (c = getchar()) != EOF ){
    int comparison_value[1] = {10}; // 10 is \n in ascii encoding
    if (c == comparison_value){ // error
        n++;
    }
}

#2

Basically '\n' is a literal expression that evaluates to a char. "\n" is a literal expression that evaluates to a pointer. So by using this expression, you are effectively using a pointer.

基本上'\n'是一个文字表达式，计算为一个字符。“\n”是计算指针的文字表达式。通过使用这个表达式，你可以有效地使用指针。

The pointer in question is pointing to a region of memory that contains an array of characters (\n in this case) followed by a termination character that tells code where the array ends.

问题的指针指向一个内存区域，该区域包含一个字符数组(本例中为\n)，后面跟着一个终止字符，该字符告诉代码数组的结束位置。

Hope that helps?

希望能帮助吗?

#1