Is it possible to export the returned value of const fn ?

[klefevre]

Hello,
Do you know if it's possible to export the returned value of a const fn e.g. mem::size_of ?

Here is an example:

#[repr(C)]
struct _PrivateStruct {
   a: i32,
   b: i32,
}

#[repr(C)]
pub const FOO: usize = std::mem::size_of::<_PrivateStruct>();

#[repr(C)]
pub struct PublicStruct {
    x: [i32; FOO],
}

Running cbindgen gives the following output where FOO isn't defined at all:

typedef struct {
    x: [i32; FOO], // FOO isn't define
} PublicStruct;

I tried some hacks like using macros, lazy_static, static variables but whether it doesn't compile or the value isn't exported.

Any thought on how to achieve this ? Any help would be very welcome :)

[eqrion]

Hmm, that's going to be tricky with cbindgen. cbindgen is just a parser of rust source code, so it doesn't have any information about compiler instrinsics like size_of. In addition, the value of size_of can vary by platform/architecture and cbindgen attempts to create a neutral header that can work on all platforms.

You might be interested in #214, which could give us a better chance at solving this.