如何防止需要复制传递给 avr-gcc C++ 构造函数的字符串? [英] How can I prevent the need to copy strings passed to a avr-gcc C++ constructor?

问题描述

在 ArduinoUnit 单元测试库中，我提供了一种为 TestSuite 命名的机制.库的用户可以编写以下内容:

In the ArduinoUnit unit testing library I have provided a mechanism for giving a TestSuite a name. A user of the library can write the following:

TestSuite suite("my test suite");
// ...
suite.run(); // Suite name is used here

这是预期的用法 - TestSuite 的名称是字符串文字.然而，为了防止难以发现的错误，我觉得有必要迎合不同的用法，例如:

This is the expected usage - the name of the TestSuite is a string literal. However to prevent hard-to-find bugs I feel obliged to cater for different usages, for example:

char* name = (char*) malloc(14);
strcpy(name, "my test suite");
TestSuite suite(name);
free(name);
// ...
suite.run(); // Suite name is used here

因此，我已经实现了这样的 TestSuite:

As such I have implemented TestSuite like this:

class TestSuite {
public:
  TestSuite(const char* name) {
    name_ = (char*) malloc(strlen(name) + 1);
    strcpy(name_, name);
  }

  ~TestSuite() {
    free(name_);
  }

private:
  char* name_;
};

抛开无法在构造函数中处理内存分配失败的问题，我更愿意简单地将指针分配给这样的成员变量:

Putting aside the issue of failing to deal with memory allocation failures in the constructor I'd prefer to simply allocate the pointer to a member variable like this:

class TestSuite {
public:
  TestSuite(const char* name) : name_(name) {
  }

private:
  const char* name_;
};

有什么方法可以更改接口以强制它正确"使用，以便我可以取消动态内存分配?

Is there any way I can change the interface to force it to be used 'correctly' so that I can do away with the dynamic memory allocation?

推荐答案

如果你提供两个重载的构造函数会怎样?

What if you provide two overloaded constructors?

TestSuite(const char* name) ...
TestSuite(char* name) ...

如果使用 const char* 调用，那么构造函数可以复制指针，假设字符串不会消失.如果使用 char* 调用，构造函数可以复制整个字符串.

If called with a const char*, then the constructor could make a copy of the pointer, assuming that the string will not go away. If called with a char*, the constructor could make a copy of the whole string.

请注意，当 name 实际上是动态分配的时，仍然可以通过将 const char* 传递给构造函数来破坏这种机制.但是，这可能足以满足您的目的.

Note that it is still possible to subvert this mechanism by passing a const char* to the constructor when the name is in fact dynamically allocated. However, this may be sufficient for your purposes.

我应该指出，我从未真正在 API 中看到过这种技术，这只是我在阅读您的问题时想到的一个想法.

I should note that I have never actually seen this technique used in an API, it was just a thought that occurred to me as I was reading your question.

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