FILE 指针神秘地重置为 NULL

发布于 2024-11-26 04:03:56 字数 750 浏览 3 评论 0原文

我正在使用 Visual stduio 2008 c++。我正在编写 Windows 窗体应用程序。我在 Form1.h 顶部声明一个 FILE* 数组作为全局值。

const int k = 1; //i need to change k to 2 sometimes. 
FILE* myFiles[k];

在 From1 的构造函数中，我使用 for 循环来打开我的文件。

for(int i = 0; i < k; ++i)
{    
  char filename[100] = "";
  sprintf(filename,"Record/record_%ld_%d.txt",g_recordName,i);
  myFiles[i] = fopen(filename,"w");
}

我为此表单设置了一个计时器，每次滴答都会将某些内容打印到 myFiles 中。到目前为止还不错，但如果我

fprintf(myFiles[0],"%d",1234);

在 for 循环之后将类似的内容放入构造函数中。这行工作正常，但是如果我要在计时器的滴答事件中打印任何内容，我发现 myFiles[0] 已经设置为 NULL！

另外，如果我在构造函数中fprintf(myFiles[0],"something")，在计时器的tick事件中FILE指针仍然不会为空。

为什么会发生这种情况？有人知道为什么吗？

原文

I'm using visual stduio 2008 c++. And I'm writing windows form application. I declare a FILE* array at the top of Form1.h as a global value

const int k = 1; //i need to change k to 2 sometimes. 
FILE* myFiles[k];

In From1's constructor, I use a for loop to fopen my files.

for(int i = 0; i < k; ++i)
{    
  char filename[100] = "";
  sprintf(filename,"Record/record_%ld_%d.txt",g_recordName,i);
  myFiles[i] = fopen(filename,"w");
}

And I set a timer for this form, each tick it will fprintf something into myFiles.
It's fine so far, but if I put something like

fprintf(myFiles[0],"%d",1234);

into constructor after the for-loop. It works OK this line, but if I'm gonna fprintf anything in timer's tick event, I found that myFiles[0] is already set to NULL!!

In addition, if I fprintf(myFiles[0],"something") in the construtor, FILE pointer still won't be null in timer's tick event.

WHY does this happen?! anyone knows why?

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