是无效**在ANSI-C可以接受的类型？ [英] Is void** an acceptable type in ANSI-C?
问题描述
我所看到的，其原型是一个函数：
I have seen a function whose prototype is:
int myfunc(void** ppt)
此函数被调用在C文件
A = MYFUNC（MYSTRUCT ** VAR1）;
This function is called in a C file as a = myfunc(mystruct **var1);
其中MYSTRUCT是的typedef结构，我们有一个。
where mystruct is typedef for one of structure we have.
这个工程没有在任何MSVC6.0编译错误，但是，当我与其他一些C编译器编译它，它给在一个地方错误的调用该函数与错误消息：
This works without any compilation errors in MSVC6.0, But when I compile it with some other C compiler, it gives an error at the place where this function is called with error message:
类型MYSTRUCT的论证**是不符合void类型的参数**
在myfunc（）的参数保持为无效**，因为它似乎是一个通用的malloc一种功能与各种结构变量类型的内存分配
The argument of myfunc() is kept as void** because it seems to be a generic malloc kind of function to be called with various structure variable types for memory allocation
- 有什么类型，如无效**允许C标准/任何C编译器？
- 如何解决这个问题？ [我试过铸造函数调用参数
MYSTRUCT **，但它没有工作]
- Is there any type such as void ** allowed in C standard/any C compilers?
- How do I fix this? [I tried casting the function call argument to
mystruct**, but it didn't work]
-AD
推荐答案
无效** 的是的有效，但是，根据您的错误信息，你可能有显式转换参数如下：
void** is valid but, based on your error message, you probably have to explicitly cast the argument as follows:
mystruct **var1;
x = myfunc ((void**) var1);
这是因为 MYFUNC 函数期待无效** 键入。而无效* 可隐式转换为任何其他指针，事实并非如此的双指针 - 你需要显式转换为
That's because the myfunc function is expecting the void** type. While void* can be implicitly cast to any other pointer, that is not so for the double pointer - you need to explicitly cast it.
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