Visual Studio 2015-编译器警告(等级2)C4146 [英] Visual Studio 2015 - Compiler Warning (level 2) C4146

问题描述

我的代码中包含以下行

signed int test_case= -2147483648;

会产生错误:

C4146一元减运算符应用于无符号类型，结果仍为无符号

C4146 unary minus operator applied to unsigned type, result still unsigned

但是这仍然是带符号整数类型的数据范围:

but this is still with the data range of teh signed integer type:

__ int32已签名，已签名int，int –2,147,483,648至2,147,483,647

__int32 signed, signed int, int –2,147,483,648 to 2,147,483,647

奇怪的是，将其分配为 signed long 会给出相同的错误，即

The strange things is assigning it as signed long gives this same error, i.e.

signed long test_case= -2147483648;

下面的更改可以编译:

signed int test_case= -2147483647;

signed int test_case= 2147483649;

signed long test_case= -214748364800;

• 有人用Visual Studio 2015编译器看到此问题吗?
• 如何定义数据类型?
• 如何检查范围?
• 为什么似乎忽略了已签名"分配?
• Has anyone seen this issue with Visual Studio 2015 compiler?
• How is it defining the data types?
• How is the range checked?
• Why does it seem to ignore the "signed" assignment?

谢谢

推荐答案

由于它是编译器错误，因此此答案特定于 MSVC ，并且错误 >从iso C ++的角度来看.有关正确和标准的答案，请参见@Bathsheba答案.(我鼓励OP接受正确的答案，而不是以后的读者使用此答案.)

Since it is a compiler bug, this answer is specific to MSVC and it is wrong from iso C++ perspective. For the correct and standard answer please see @Bathsheba answer. (I encourage the OP to accept the correct answer instead of this answer for future readers).

从 MSDN :

对数字2147483648进行求值.因为它大于 最大整数值2147483647，不是2147483648的类型 整数，但无符号整数.

The number 2147483648 is evaluated. Because it is greater than the maximum integer value of 2147483647, the type of 2147483648 is not int, but unsigned int.

换句话说，编译器会将-2147483648视为-，将2147483648视为-2147483648.因此2147483648部分被认为是unsigned int，因为它比int大.然后编译器将应用-运算符，从而导致出现此警告.

In other words, the compiler will deal with -2147483648 as - and 2147483648 not as -2147483648. So the 2147483648 part is considered as unsigned int since it is bigger than int. and then the compiler applies the - operator which is leading to this warning.

解决方案:

auto test_case= -2147483648ll;

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