Issue 1026: thrd_t as an array type

Authors: Jay Ghiron
Date: 2026-02-27
Submitted against: C23
Status: Open
Cross-references: 1058

No wording exists currently to say that thrd_t is not an array type:

The types are

...

thrd_t

which is a complete object type that holds an identifier for a thread;

(C23 7.28.1 "Introduction" paragraph 4).

However, the definition of thrd_current returns a thrd_t:

thrd_t thrd_current(void);

(C23 7.28.5.2 "The thrd_current function" paragraph 1).

Functions are not allowed to return arrays, so if thrd_t were an array type then this declaration would be invalid.

Suggested correction

Modify C23 7.28.1 paragraph 4:

thrd_t

which is a complete object type other than an array type that holds an identifier for a thread;

Comment from Issues list maintainer on 2026-08-21:

This issue was discussed at the August 2026 (Ottawa) meeting of WG14. It was suggested that, rather than array types being excluded individually in particular cases, the general wording about library types should exclude them by default, with only a few specific cases such as jmp_buf and va_list allowing them. Joseph Myers took an action item to propose wording for this (building on the wording for issue 1025).

Comment from Issues list maintainer on 2026-08-25:

In reflector message 37708, Joseph Myers provided an analysis of which standard library types are not currently excluded from being array types.