C 警告(clang 编译器) "integer literal is too large to be represented in a signed integer"

Question

我有这段代码

#include <stdio.h>

typedef signed long long v2signed_long 
      __attribute__ ((__vector_size__ (sizeof(signed long long) * 2)));

int main()
{
        v2signed_long v = {4611686018427387904LL, -9223372036854775808LL};

        printf("%lli, %lli\n", v[0], v[1]);
        return 0;
}

给出以下警告(相关问题没有帮助):

:7:45: warning: integer literal is too large to be represented in
       a signed integer type, interpreting as unsigned
  [-Wimplicitly-unsigned-literal]
    v2signed_long v = {4611686018427387904LL, -9223372036854775808LL};

有没有办法解决这个警告？谢谢!

Answer 1

问题是 -9223372036854775808LL 实际上不是整数文字。它是应用了一元 - 运算符的文字 9223372036854775808LL。值 9223372036854775808 太大而不适合 signed long long，这就是您收到警告的原因。

您可以改用表达式 -9223372036854775807LL - 1LL 来解决这个问题。值 9223372036854775807 适合 signed long long 和 -9223372036854775807LL 一样，然后减去 1 即可得到所需的值。

或者，您可以使用宏LLONG_MIN。