empty structs

[cath8024]

can somebody give me a use for a struct with no member variables.

[reon]

please make the question clear....

struct is equal to class keyword in C++.

the difference is class is holding private as default access specifier and struct is having public..
And there is no need to mention access specifiers inside struct....default is public...

[cath8024]

Consider a struct as below.
struct Test1 {};
I got from the net that C++ allows empty struct or class (gcc 4.0 supports empty struct even in C). Empty struct/class can be used as a placeholder for future development.
Can somebody illustrate how an empty struct can be used as a placeholder.

[cath8024]

An empty struct has no member variables.
Then for what purpose do we use them?
please help me.

[JosAH]

If you add an empty struct as the first member of another struct, the empty
struct can serve as a "marker interface", i.e. when you cast a pointer to that
outer struct to a pointer of the inner struct and the cast succeeds you know
that the outer struct is "marked" as something. This just works when you use
C++ though; for C there is little use for an empty struct.

kind regards,

Jos

[Banfa]

cath8024

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Banfa
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