https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120102
Bug ID: 120102
Summary: function prototype with array of forward declared
struct is incomplete?
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: izaberina at gmail dot com
Target Milestone: ---
this code forward declares a struct and it's accepted:
```
struct foo;
void f(struct foo *arg);
```
this version is rejected:
```
struct foo;
void g(struct foo arg[]);
```
they are completely equivalent after adjustment of parameters, and of course
it's possible to assign things between them: https://godbolt.org/z/4zr3YWhrP
basically all versions of gcc and clang on godbolt accept the former and reject
the latter. for whatever reason, msvc is cool with both:
https://godbolt.org/z/fzPExThx7
the following is the relevant text from c17:
> 6.7.6.3 Function declarators (including prototypes)
> ...
> 4. After adjustment, the parameters in a parameter type list in a function
> declarator that is part of a definition of that function shall not have
> incomplete type.
> ...
> 7. A declaration of a parameter as "array of type" shall be adjusted to
> "qualified pointer to type", where the type qualifiers (if any) are those
> specified within the [ and ] of the array type derivation.
i do find it unlikely that both gcc and clang are wrong on this, but i really
think both versions should be accepted, as they are equivalent. can some
language lawyer chime in?
