如何初始化在C的malloc静态指针？ [英] How to initialize static pointer with malloc in C?

问题描述

我试图启动一个静态变量（函数内）在C的malloc，但我得到了初始不恒定的错误。我知道我不能启动在C非常量静态的，但任何人都可以想到了解决办法？我需要code有，因为这同样的效果：

I'm trying to initiate a static variable (inside a function) with malloc in C, but I'm getting the "initializer not constant error". I know that I can't initiate a static with non constants in C, but can anyone think of a solution? I need the code to have the same effect as this:

static int *p = (int *)malloc(sizeof(int));

有没有窍门/解决方法吗？

Is there a trick/workaround?

编辑：我有一个名为每个标志变为高电平时功能。在这个函数中，我创建并启动一个新的线程。我宣布一个指向一个struct和使用malloc分配内存那么这​​个指针传递给线程。然后，该函数返回控制。当我重新输入的功能，我刚打开的线程仍在运行，我想能够访问我原本传递给线程的内存区域。这就是为什么我需要一个静态的，这样我可以的malloc在第一次通话，然后在后续调用使用相同的地址。这样我可以从线程信息。所有这一切都避免使用全局变量。

I have a function that is called every time a flag goes high. In this function, I'm creating and starting a new thread. I declare a pointer to a struct and use malloc to allocate memory then pass this pointer to the thread. Then the function returns control. When I re-enter the function, the thread that I opened initially will still be running and I want to be able to access the memory region that I originally passed to the thread. That's why I need a static so that I can malloc on the first call and then use the same address on subsequent calls. This way I can get info from the thread. All this to avoid using global variables.

推荐答案

假设你想要的功能，静态变量：

Assuming you want function-static variables:

int foo(void) {
    static int b=1;
    static int *p;
    if (b) {
        p =  malloc(sizeof(int));
        b = 0;
    }
    ...
}

您可以使用NULL值的p作为检查，只要你的知道的它永远不会是 NULL 第一次通话后。

You can use NULL value for p as a check, as long as you know it will never be NULL after the first call.

记住要检查在malloc的错误;它是一个的运行时的分配，并且当将不再需要它也应该被释放。

Remember to check for errors in malloc; it is a runtime allocation, and should also be freed when it will not be needed anymore.

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