Undefined behaviour of struct without members

[KenjiroLotus]

The tasks

• c/ldv-regression/rule57_ebda_blast.i
• c/ldv-regression/rule57_ebda_blast_2.i
• c/ldv-regression/rule57_ebda_blast.c_1.i

contain a struct without members. After the C standard this leads to an undefined behaviour.

(C17, 6.7.2.1 Structure and union specifiers p8) "If the struct-declaration-list does not contain any named members, either directly or via an anonymous structure or anonymous union, the behavior is undefined."

However, this is allowed through a GNU C extension:

GCC permits a C structure to have no members:

struct empty {};

The structure has size zero

https://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html

The question is now wether this should be handled as an undefined behaviour or as a struct with size zero as specified in the GNU C extension.

[PhilippWendler]

The C programs in this repo are in general GNU C programs as mentioned in the readme. So it should be handled as struct with size 0.