将std :: string传递给函数f（** char） [英] Pass std::string to a function f(**char)

问题描述

是否可以将std :: string的指针传递给需要** char的函数？

Is it possible to pass the pointer of a std::string to a function which expects a **char? The function expects a **char in order to write a value to it.

目前我正在做以下操作：

Currently I am doing the following:

char *s1;
f(&s1);
std::string s2 = s1;

有没有更短的路？很明显，s2.c_str（）不工作，因为它返回 const * char 。

Is there no shorter way? It is obvious, that s2.c_str() does not work, since it returns const *char.

推荐答案

这是处理这类函数的适当方法。你不能直接传递 std :: string ，因为你可以将它转换为C字符串，它在内存中的布局是不同的，所以被调用的函数不知道在哪里放它的结果。

That's the appropriate way to handle that sort of function. You cannot pass in the std::string directly because, while you can convert it to a C string, it is laid out in memory differently and so the called function would not know where to put its result.

然而，如果可能，你应该重写函数，所以它需要一个 std： ：string& 或 std :: string * 作为参数。

If possible, however, you should rewrite the function so it takes a std::string& or std::string * as an argument.

，请确保 free（）或 delete [] c $ c> f（）是确定是否需要这样做。）

(Also, make sure you free() or delete[] the C string if appropriate. See the documentation for whatever f() is to determine if you need to do so.)

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