为什么 C++ 允许将整数分配给字符串? [英] Why does C++ allow an integer to be assigned to a string?

问题描述

我今天在一个程序中遇到了一个有趣的情况，我无意中将一个无符号整数分配给了一个 std::string.VisualStudio C++ 编译器没有给出任何警告或错误，但我在运行项目时碰巧注意到了这个错误，它为我的字符串提供了垃圾字符.

I encountered an interesting situation today in a program where I inadvertantly assigned an unsigned integer to a std::string. The VisualStudio C++ compiler did not give any warnings or errors about it, but I happened to notice the bug when I ran the project and it gave me junk characters for my string.

代码大概是这样的:

std::string my_string("");
unsigned int my_number = 1234;
my_string = my_number;

以下代码也可以很好地编译:

The following code also compiles fine:

std::string my_string("");
unsigned int my_number = 1234;
my_string.operator=(my_number);

以下导致错误:

unsigned int my_number = 1234;
std::string my_string(my_number);

这是怎么回事?为什么编译器会用最后一个代码块停止构建，而让前 2 个代码块构建?

What is going on? How come the compiler will stop the build with the last code block, but let the first 2 code blocks build?

推荐答案

因为 string 可以从 char 赋值，而 int 可以隐式转换为 char.

Because string is assignable from char, and int is implicitly convertible to char.

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