struct - Empty structure in C

Question

I have a structure with no members (for the moment) and I would like to know if it is possible to suppress the warning I get:

warning: struct has no members

Is it possible to add a member and keep the sizeof the struct zero? Any other solution?

Answer 1

In c the behaviour of an empty structure is compiler dependent versus c++ where it is part of the spec (explanations here)

C++
A class with an empty sequence of members and base class objects is an empty class. Complete objects and member subobjects of an empty class type shall have nonzero size.

in C it is rather more murky since the c99 standard has some language which implies that truly empty structures aren't allowed (see TrayMan's answer) but many compilers do allow it (e.g gcc).

Since this is compiler dependent it is unlikely that you will get truly portable code in this case. As such non portable ways to suppress the warning may be your best bet.

• In VS you would use #pragma warning
• in GCC from 4.2.1 you have Diagnostic Pragmas