c - C 标准是否将真值明确表示为 0 或 1？

Question

我们知道任何不等于0的数字在C中都被视为true，所以我们可以这样写:

int a = 16;

while (a--)
    printf("%d\n", a);  // prints numbers from 15 to 0

但是，我想知道 true/false 在 C 中是否被定义为 1/0，所以我尝试了下面的代码:

printf("True = %d, False = %d\n", (0 == 0), (0 != 0));  // prints: True = 1, False = 0

C 标准是否明确指出 true 和 false 的真值分别为 1 和 0？

Answer 1

Does the C standard explicitly indicate the truth values of true and false as 0 and 1 respectively?

C 标准将 true 和 false 定义为 stdbool.h 中的宏，扩展为 1 和 0 分别。

C11-§7.18:

The remaining three macros are suitable for use in #if preprocessing directives. They are

true

which expands to the integer constant 1,

false

which expands to the integer constant 0 [...]

对于运算符 == 和 != ，标准说

C11-§6.5.9/3:

The == (equal to) and != (not equal to) operators are analogous to the relational operators except for their lower precedence.¹⁰⁸⁾ Each of the operators yields 1 if the specified relation is true and 0 if it is false. The result has type int. For any pair of operands, exactly one of the relations is true.