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I saw a lot of codes like:

void foo(void* arg)
void bar(void** arg)
f((void*)p)

but what does void pointer mean in c? I just know it stands for generic
pointer.

thanks.

Niu Xiao <> writes:
> I saw a lot of codes like:
>
> void foo(void* arg)
> void bar(void** arg)
> f((void*)p)
>
> but what does void pointer mean in c? I just know it stands for
> generic pointer.

Right, it's a generic pointer. I'm not sure what you're asking.

"void" is a special type, an incomplete type that cannot be completed.
You can't have an object of type void; a function that returns void
doesn't return a value.

Type "void*" is a pointer type that can point to any object. An
object of type void* can hold a value of any pointer-to-object type.
Any object type can be implicitly converted to void*, and vice versa.

--
Keith Thompson (The_Other_Keith) kst- <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

On Wed, 03 May 2006 04:58:09 GMT, Keith Thompson <kst-> wrote
in comp.lang.c:

> Niu Xiao <> writes:
> > I saw a lot of codes like:
> >
> > void foo(void* arg)
> > void bar(void** arg)
> > f((void*)p)
> >
> > but what does void pointer mean in c? I just know it stands for
> > generic pointer.
>
> Right, it's a generic pointer. I'm not sure what you're asking.
>
> "void" is a special type, an incomplete type that cannot be completed.
> You can't have an object of type void; a function that returns void
> doesn't return a value.
>
> Type "void*" is a pointer type that can point to any object. An
> object of type void* can hold a value of any pointer-to-object type.
> Any object type can be implicitly converted to void*, and vice versa.

Of course you meant your last sentence above to read:

A pointer to any object type can be implicitly converted to void*, and
vice versa.

--
Jack Klein
Home: http://JK-Technology.Com
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alt.comp.lang.learn.c-c++
http://www.contrib.andrew.cmu.edu/~a...FAQ-acllc.html

Jack Klein <> writes:
> On Wed, 03 May 2006 04:58:09 GMT, Keith Thompson <kst-> wrote
> in comp.lang.c:
[...]
>> Type "void*" is a pointer type that can point to any object. An
>> object of type void* can hold a value of any pointer-to-object type.
>> Any object type can be implicitly converted to void*, and vice versa.
>
> Of course you meant your last sentence above to read:
>
> A pointer to any object type can be implicitly converted to void*, and
> vice versa.

Yes, thanks.

--
Keith Thompson (The_Other_Keith) kst- <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

Keith Thompson wrote:
> Niu Xiao <> writes:
>
>>I saw a lot of codes like:
>>
>>void foo(void* arg)
>>void bar(void** arg)
>>f((void*)p)
>>
>>but what does void pointer mean in c? I just know it stands for
>>generic pointer.
>
>
> Right, it's a generic pointer. I'm not sure what you're asking.
>
> "void" is a special type, an incomplete type that cannot be completed.
> You can't have an object of type void; a function that returns void
> doesn't return a value.
>
> Type "void*" is a pointer type that can point to any object. An
> object of type void* can hold a value of any pointer-to-object type.
> Any object type can be implicitly converted to void*, and vice versa.
>

> Any object type can be implicitly converted to void*, and vice versa.
This sentence tells everything, thanks.

Niu Xiao <> writes:
> Keith Thompson wrote:
[...]
> > Any object type can be implicitly converted to void*, and vice versa.
> This sentence tells everything, thanks.

Except that it's wrong.

Any pointer-to-object type (not any object type) can be implicitly
converted to void*, and vice versa.

--
Keith Thompson (The_Other_Keith) kst- <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.