警告：在隐式常量转换中溢出 [英] Warning : overflow in implicit constant conversion

问题描述

在下面的程序中，第5行给出了预期的溢出警告，但令人惊讶的是第4行在GCC中没有给出任何警告：http://www.ideone.com/U0BXn

In the following program, the line 5 does give overflow warning as expected, but surprisingly the line 4 doesn't give any warning in GCC: http://www.ideone.com/U0BXn

int main()
{
    int i = 256;
    char c1 = i;    //line 4
    char c2 = 256;  //line 5
    return 0;
}

我想这两行应该给予溢出警告。

导致我做这个实验的话题是： typedef类型检查？

The topic which led me to do this experiment is this: typedef type checking?

我说下面的我从我的回答中删除，因为当我运行它，它没有显示出我的预期）：

There I said the following(which I deleted from my answer, because when I run it, it didn't show up as I had expected):

//However, you'll get warning for this case:

typedef int  T1;
typedef char T2;

T1 x = 256;     
T2 y = x; //possible overflow warning! (but it doesn't give warning :()

推荐答案

-Wall 不包含许多选项。 -Wconversion 是其中之一，警告您感兴趣的行为

-Wall doesn't include many options. -Wconversion is one of them and warns about the behavior you're interested in.

请参阅 http：// gcc。 gnu.org/onlinedocs/gcc/Warning-Options.html

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