HL/C compilation fails with Visual Studio when Haxe field is named restrict, _restrict, or __restrict

[joshtynjala]

The C code for HashLink, when generated from the following Haxe code, cannot be compiled with Visual Studio's C compiler, cl.exe. It works with MinGW's gcc (and gcc on macOS and Linux), though.

class HlcRestrict {
	static function main() {
		new HlcRestrict();
	}

	public function new() {
	}

	public var restrict:String;
}

Compiled with the following options:

--main HlcRestrict
--hl generated/HlcRestrict.c

cl.exe command in Visual Studio developer shell:

 cl.exe /Ox /Fe:HlcRestrict.exe -I "<hashlink>\include" -I "generated" "generated/HlcRestrict.c" "<hashlink>\libhl.lib"

It results in the following error:

generated_std/HlcRestrict.h(22): error C2208: '_String *restrict ': no members defined using this type

Same result if you change it to _restrict or __restrict (one or two underscores).

public var _restrict:String;

public var __restrict:String;

However, if you change it to ___restrict with three underscores, cl.exe can successfully compile the generated C code:

public var ___restrict:String;

It looks like src/generators/hl2c.ml already has some code to rewrite certain field names when they conflict with C keywords, including restrict actually, but I guess that this behavior is specific to Visual Studio's C compiler that appears to have been missed.

[Apprentice-Alchemist]

Looks like the escaping used by HL2C will turn restrict into _restrict.
But, _restrict and __restrict are also keywords for MSVC apparently.

The best solution here is probably to do what genccp does:
prefix reserved identifiers with _hx_, and do the same for any identifier that starts with __ (since according to the C standard those are also reserved).

(This page has an overview of the exact rules: https://en.cppreference.com/w/c/language/identifier)
(For an overview of MSVC specific keywords: https://learn.microsoft.com/en-us/cpp/c-language/c-keywords)

[joshtynjala]

@kLabz

Haxe 4.3.3 fixes the issue with a field named restrict. Unfortunately, _restrict and __restrict still cause compilation failure with Visual Studio's cl.exe.

As far as I can tell, I don't think that any changes were made to fix _restrict. That one probably needs to be added to the keywords list explicitly in the (* MS specific *) section.

I don't know OCaml, but I was looking at this line that should have fixed __restrict:

let ident i = if (Hashtbl.mem keywords i) || (ExtString.String.starts_with "__" i) then "_hx_" ^ i else i

The ExtString.String.starts_with docs say:

starts_with s x return true if s is starting with x.

Again, I've never touched OCaml, except to read the Haxe compiler code, but I think that you might have gotten the two arguments backwards. Maybe it should have been this instead?

ExtString.String.starts_with i "__"

[kLabz]

ahem yeah that's possible. as for _restrict, I need to add it too indeed