英文:
Which windows.h header defines NULL?
问题
在某个时候，我需要在Windows代码中检查NULL，但我不想包含stdio.h或stdlib.h。
我强烈怀疑NULL在windows.h的某个地方被定义，但我找不到页面。我找到了这个，这很有趣，但没有告诉我我想要知道的信息。
英文:
I have to write some Windows code, and I want to separate it from the Linux part as much as possible.
At one point I need to check for NULL in the Windows code, but I don't want to include stdio.h or stdlib.h.
I strongly suspect that NULL is defined somewhere in windows.h, but I can't find the page. I found this, which is interesting, but doesn't tell me what I want to know.
答案1
得分: 8
NULL 在标准的 C 头文件 stddef.h 中定义，句号。
如果你在 Windows 上运行例如 gcc/mingw 端口，你只需告诉任何半靠谱的 IDE 找到 NULL 的声明，并最终进入 stddef.h，其中写着 #define NULL ((void *)0)。
你还可以创建一个这样的源文件：
// main.c
#include <windows.h>
int main (void)
{}
然后使用 gcc main.c -H 进行编译。这将展开所有头文件的依赖关系，这样你就会看到哪个头文件包含了哪些其他头文件。你会得到一大堆头文件，并且你会注意到 stddef.h 间接地包含在大约 2-3 个不同的位置。
结论：NULL 不是由 windows.h 或任何其他应该直接包含的 Windows 特定头文件定义的。
如果你需要使用 NULL，则正确的方法是 #include <stddef.h>，不论操作系统如何。
英文:
NULL is defined in the standard C header stddef.h, period.
If you run for example gcc/mingw port in Windows, you can just tell any half-decent IDE to find the declaration of NULL and end up in stddef.h where it says #define NULL ((void *)0).
You can also create a source file like this:
// main.c
#include <windows.h>
int main (void)
{}
Then compile with gcc main.c -H. This will expand all header dependencies, so you'll see which header that includes what other headers. You'll get a whole flood of them and you'll notice that stddef.h is indirectly included at some 2-3 different locations.
Conclusion: NULL is not defined by windows.h or any other windows-specific header that you should be including directly.
If you need to use NULL, then the correct approach is to #include <stddef.h> regardless of OS.
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