What does void pointer actually mean?

[Niu Xiao]

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.

[Keith Thompson]

Niu Xiao <gn******@gmail.com> 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) ks***@mib.org <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.

[Jack Klein]

On Wed, 03 May 2006 04:58:09 GMT, Keith Thompson <ks***@mib.org> wrote
in comp.lang.c:

Niu Xiao <gn******@gmail.com> 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

[Keith Thompson]

Jack Klein <ja*******@spamcop.net> writes:

On Wed, 03 May 2006 04:58:09 GMT, Keith Thompson <ks***@mib.org> 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) ks***@mib.org <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.

[Niu Xiao]

Keith Thompson wrote:

Niu Xiao <gn******@gmail.com> 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.

[Keith Thompson]

Niu Xiao <gn******@gmail.com> 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) ks***@mib.org <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.