I am calling a C function, described in D as

extern (C) GtkWidget* gtk_menu_item_new_with_label (immutable(char)*);

I call it like this

accounts_menu_item = gtk_menu_item_new_with_label("New account (Ctrl-n)");

The type of the string literal in the call is immutable(char)[]. The type of the parameter is a pointer to immutable characters.

This setup works.

My question is about the documentation vs. what is really going on here.

Section 12.17 of the Language Reference does not indicate any circumstance in which a dynamic array, which the literal is, is implicitly coerced to a pointer. I realize that this is a special case -- the callee is a C function -- that might not be covered by this section. So I looked at Section 32.3, Chapter 32 being "Interfacing to C". 32.3 contains a table of correspondences between D and C types. The entry for the D type T[] indicates no correspondence in C.

So at least my reading of the documentation suggests that my code should not compile. And yet it does and works, which leads me to believe there is a documentation error that ought to be reported.

Before doing so, I decided to send this message so those of you who know D a lot better than I do can tell me what I've missed or gotten wrong, if that is the case.

Thanks --
/Don

On Monday, 18 October 2021 at 15:04:11 UTC, Don Allen wrote:

This is a special case for string literals, covered in section 10.23.7.

On Monday, 18 October 2021 at 15:34:45 UTC, Paul Backus wrote:

Yes. Thank you.

On Monday, 18 October 2021 at 15:58:35 UTC, Don Allen wrote:

I do think it would be helpful, even essential, to have a link in Section 12.17 to the section you cite. The Language Reference is just that, a reference, not a tutorial and it should not be a requirement to read it from cover to cover. Strings and string literals are arrays and 12.17 purports to cover the implicit type conversions among the various array types, but currently leaves out this special case and should not, in my opinion. I will file an issue making this suggestion.