英文:
who is managing the memory of C lib like "strtok"
问题
当我想要使用C标准库函数如strtok时，我发现它提供了一个指向堆内存的指针。我想使用C++ RAII来管理这个堆指针，但我发现无法释放它。是否有人在管理这部分内存？或者我如何确认它的生命周期？
英文:
when I want to use C lib function like strtok, I found it provided a point of heap, I want to manage this heap pointer with CPP RAII.
but I found I cannot free it, is it someone managing this part of memory? or how could I confirm its lifecycle?
答案1
得分: 6
strtok与堆无关。它不分配内存，而是返回一个指针，指向作为第一个参数传递给最后一次非空第一个参数调用的char数组内部。这个数组会因为副作用而被修改。
这个C函数具有令人困惑和容易出错的语义，它在许多目标上不可重入且不线程安全。
我建议您根本不要在C++代码中使用这个函数，特别是在需要实现RAII的情况下。
应该有C++替代方法，作为std::string类型的成员函数。
如果您想在C中编程，请考虑替代方案，如strtok_r、strsep或使用strspn和strcspn来分析字符串，这些方法不会修改源字符串，并使用strndup从堆中分配标记。
英文:
strtok does not have anything to do with the heap. It does not allocate memory, it returns a pointer inside the array of char passed as the first argument to the last call with a non null first argument. This array is modified as a side-effect.
This C function has confusing and error prone semantics, it is non reentrant and not thread safe on many targets.
I recommend you do not use this function at all, especially in c++ code where you want to implement RAII.
There should be c++ alternatives available as methods of the std::string type.
If you want to program in C, consider alternatives such as strtok_r, strsep or analyzing the string using strspn and strcspn, which to not modify the source string, and allocating the tokens from the heap with strndup.
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