Enable warnings for empty structure

Question

I have a question about empty structures in C. As far as I can tell from reading the standards, it seems that they are not allowed:

6.2.5-20

- The type of structure describes a sequentially allocated non-empty set of member objects (and, in some cases, an incomplete array), each of which has an optional specified name and, possibly, a separate type.

So, no wonder when you try to compile something like:

struct foo { }; 

There is some error in MS VS:

bug C2016: C requires a structure or union to have at least one element

However, when compiling the same code with gcc -Wall -Werror , no errors are visible. So that...

• Am I reading the specification correctly that this is not allowed in C? (and more surprisingly, Microsoft got it right ?!)
• Is there an option that can be passed to gcc to catch this problem?

Answer 1

• Yes, a memberless structure type is not valid in C.

• -Werror -pedantic with gcc will stop the translation.