bindgen generates a static mut where a const is expected

[alex]

Input C/C++ Header

#define __GFP_IO                0x40u
#define GFP_KERNEL (__GFP_IO)

const unsigned BINDING_GFP_KERNEL = GFP_KERNEL;

Bindgen Invocation

$ bindgen t.h

Actual Results

/* automatically generated by rust-bindgen */

pub const __GFP_IO: u32 = 64;
pub const GFP_KERNEL: u32 = 64;
extern "C" {
    #[link_name = "\u{1}BINDING_GFP_KERNEL"]
    pub static mut BINDING_GFP_KERNEL: ::std::os::raw::c_uint;
}

Expected Results

I expected BINDING_GFP_KERNEL to be generated as pub const BINDING_GFP_KERNEL = ...

[emilio]

Which versión of libclang is this using? I'd expect clang 4.0+ to generate the expected results

[alex]

wontfix per discussion on IRC

[WiSaGaN]

Any detailed explanation for the won't fix? Was it the use of a wrong libclang?

[geofft]

Yes. From my IRC logs, Alex was asked, "which libclang version are you using? Clang <= 3.9 doesn't offer APIs to resolve the actual values of constants, so we fall back to the following most likely thing to work which isn't really that great," to which he replied 3.8 and said using a newer version from https://apt.llvm.org fixed the bug. (If you're on Debian/Ubuntu, apt.llvm.org is a reasonable place to get things and is run by the same folks who package LLVM in Debian.)