警告：（751）常量表达式中的算术溢出

嗨，那里。当我编译这个项目时，我遇到了这个警告。这里是我的代码：警告显示：困难。C：53：警告：（751）常数表达式中的算术溢出，然后我看了XC8编译器用户指南，并说：这个警告也可以由中间值溢出触发。例如：无符号int i；/*假定INT是16位宽*/i＝240×137；/*这应该可以，对不对？*用计算器快速检查显示240×137是32880，它可以很容易地存储在无符号int中，但是会产生警告。为什么？因为240和137都是int值。因此，乘法的结果也必须是符号int值，但已签名的int不能保存值32880。（两个操作数都是常数值，所以代码生成器可以在编译时评估这个表达式，但它必须遵从所有ANSI C规则。）下面的代码强制执行用未签名的结果：I= 240U* 137；/*强制至少一个操作数为无符号*/所以我把我的代码改成：但是，它仍然不能工作。然后我再次查看XC8编译器用户指南，它说（附件1）问题：后缀U或U支持无符号短长？或者我需要改变数据类型从无符号短长到无符号长，后缀U还是U？



      以下为原文

    Hi, there. I run into this warning when I compiled the project.
Here is my code:
#define MINUTES(x) x*60*1000 //macro


unsigned short long UV_CountDown = MINUTES(120);
unsigned short long CVCountDown = MINUTES(130);
unsigned short long WHOLE_CountDown = MINUTES(500);
unsigned short long reparingCountDown = MINUTES(5);

unsigned int jobtimerCountDown = MINUTES(1);

and warning shows:

difficult.c:53: warning: (751) arithmetic overflow in constant expression

Then I took a look XC8 compiler user guide and it says:

This warning can also be triggered by intermediate values overflowing. For example:
unsigned int i; /* assume ints are 16 bits wide */
i = 240 * 137; /* this should be okay, right? */
A quick check with your calculator reveals that 240 * 137 is 32880 which can easily be
stored in an unsigned int, but a warning is produced. Why? Because 240 and 137
and both signed int values. Therefore the result of the multiplication must also be
a signed int value, but a signed int cannot hold the value 32880. (Both operands
are constant values so the code generator can evaluate this expression at compile
time, but it must do so following all the ANSI C rules.) The following code forces the
multiplication to be performed with an unsigned result:
i = 240u * 137; /* force at least one operand to be unsigned */

So I changed my code into:
#define MINUTES(x) x*60*1000 //macro


unsigned short long UV_CountDown = MINUTES(120u);
unsigned short long CVCountDown = MINUTES(130u);
unsigned short long WHOLE_CountDown = MINUTES(500u);
unsigned short long reparingCountDown = MINUTES(5u);

unsigned int jobTimerCountDown = MINUTES(1u);

BUT, it's still not working.... then I took a look XC8 compiler user guide again and it says(attachment 1)

Question: does suffix u or U support unsigned short long? or I need to change data type from unsigned short long to unsigned long followed by suffix u or U?


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