Re: [PATCH] rust: fix bindgen build error with fstrict-flex-arrays

[Andrea Righi]

On Tue, Aug 15, 2023 at 02:06:36PM +0200, Miguel Ojeda wrote:
> On Tue, Aug 15, 2023 at 8:54 AM Andrea Righi <andrea.righi@xxxxxxxxxxxxx> wrote:
> >
> > Commit df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3") enabled
> > '-fstrict-flex-arrays=3' globally, but bindgen does not recognized this
> 
> It may be more accurate to say libclang here (bindgen forwards the options).
> 
> Also, df8fc4e934c1 did it so only conditionally (if the C compiler
> supports it). This explains what you are seeing: if I am right, you
> are compiling with a modern enough GCC, which enables the option, but
> with an old enough Clang.

Oh yes, indeed! I'm using clang/libclang-14 with gcc-13, if I switch to
clang-15 everything seems fine, so I can simply move to this version.

> 
> > compiler option, triggering the following build error:
> >
> >  error: unknown argument: '-fstrict-flex-arrays=3', err: true
> 
> This should only be true with libclang < 16, since Clang 16
> implemented the option, right?
> 
> In fact, Clang 15 seems to work too -- it seems the compiler does not
> error if the option is not within [0,3] (unlike GCC).

The combo gcc-13 + libclang-15 seems to work in my case, instead with
libclang-16 I get this:

  BINDGEN rust/bindings/bindings_generated.rs
  thread 'main' panicked at '"ftrace_branch_data_union_(anonymous_at__/_/include/linux/compiler_types_h_146_2)" is not a valid Ident', /build/rust-bindgen-0.56-DgAMvF/rust-bindgen-0.56-0.56.0/debian/vendor/proc-macro2-1.0.24/src/fallback.rs:693:9

Thanks,
-Andrea