警告C26454:算术溢出:“-"运算在编译时产生负无符号结果(io.5) [英] Warning C26454: Arithmetic overflow: '-' operation produces a negative unsigned result at compile time (io.5)

问题描述

代码分析:

ON_NOTIFY(TCN_SELCHANGE, IDC_TAB_HISTORY_TYPE,
  &CAssignHistoryDlg::OnTcnSelchangeTabHistoryType)

警告C26454:

算术溢出:-"运算产生负无符号结果 在编译时(io.5).

Arithmetic overflow: '-' operation produces a negative unsigned result at compile time (io.5).

TCN_SELCHANGE的定义是:

#define TCN_FIRST (0U-550U)
#define TCN_SELCHANGE           (TCN_FIRST - 1)

我看不到我还能做些什么！

I can't see what else I can do!

推荐答案

您正在尝试从较小的无符号值中减去较大的无符号值，这会导致结果换行为零.在您的情况下，我假设将TCN_FIRST定义为0，因此将TCN_SELCHANGE设置为1将解决此问题.

You are trying to subtract a larger unsigned value from a smaller unsigned value and it's causing the result to wrap past zero. In your case, I assume TCN_FIRST is defined as 0 so setting TCN_SELCHANGE to one will fix the problem.

您还应该使用constexpr或const而不是定义.

You should also be using constexpr or const instead of defines anyway.

根据MSDN:

C ++核心检查中的算术溢出检查

C26451 RESULT_OF_ARITHMETIC_OPERATION_CAST_TO_LARGER_SIZE :[操作员]操作结束了0，并在编译时产生一个大的无符号数.此警告表明减法运算会产生否定结果，该结果在无符号上下文中进行了评估.这将导致结果回绕到0并产生一个非常大的无符号数字，这可能导致意外的溢出.

C26451 RESULT_OF_ARITHMETIC_OPERATION_CAST_TO_LARGER_SIZE :[operator] operation wraps past 0 and produces a large unsigned number at compile time. This warning indicates that the subtraction operation produces a negative result which was evaluated in an unsigned context. This causes the result to wrap past 0 and produce a really large unsigned number, which can result in unintended overflows.

1 // Example source:
2 unsigned int negativeunsigned() {
3    const unsigned int x = 1u - 2u; // C26454 reported here
4    return x;
5 }

1 // Corrected source:
2 unsigned int negativeunsigned() {
3     const unsigned int x = 4294967295; // OK
4     return x;
5 }

在更正后的源中，为未签名的结果分配了一个正值.

In the corrected source, a positive value was assigned to the unsigned result.

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