Nonzero pointer address spaces are silently erased in generated bindings and static wrappers

[lwz23]

Input C/C++ Header

static inline int __attribute__((address_space(1))) *
phase8_as1_identity(
    int __attribute__((address_space(1))) *value
) {
    return value;
}

Clang accepts this declaration on the target used below. The function takes
and returns an address space 1 pointer.

Bindgen Invocation

$ bindgen input.h \
    --wrap-static-fns \
    --wrap-static-fns-path wrapper \
    --rust-target 1.75 \
    --no-layout-tests \
    --no-rustfmt-bindings \
    --output bindings.rs

Actual Results

The generated Rust declaration silently uses ordinary pointers:

extern "C" {
    #[link_name = "phase8_as1_identity__extern"]
    pub fn phase8_as1_identity(
        value: *mut ::std::os::raw::c_int,
    ) -> *mut ::std::os::raw::c_int;
}

The generated C wrapper drops the address space too:

int *phase8_as1_identity__extern(int *value) {
    return phase8_as1_identity(value);
}

Clang rejects that wrapper:

error: passing 'int *' to parameter of type
'__attribute__((address_space(1))) int *' changes address space of pointer

The two declarations also lower to different LLVM function types. These are
the signatures from the tools listed below:

; clang-15, correct C wrapper
define dso_local i32 addrspace(1)* @phase8_as1_identity__extern(
    i32 addrspace(1)* %value)

; rustc 1.75, caller using the generated binding
declare noundef ptr @phase8_as1_identity__extern(ptr noundef)

Expected Results

Bindgen should not emit an ordinary pointer for a nonzero address space.

The C wrapper can preserve the source declaration:

int __attribute__((address_space(1))) *
phase8_as1_identity__extern(
    int __attribute__((address_space(1))) *value
) {
    return phase8_as1_identity(value);
}

Stable Rust does not have a general source-level pointer type for arbitrary
LLVM address spaces. If the selected Rust output cannot represent this type,
I would expect bindgen to diagnose it and omit the misleading declaration
instead of changing it to *mut c_int.

Environment

bindgen current main: 9d26c6eddeff9192ddedb563192abe3128fc5aae
bindgen release:      0.72.1
clang:                15.0.7
rustc:                1.75.0
target:               x86_64-unknown-linux-gnu

Current main and 0.72.1 both generate the same invalid wrapper at O0 and O2.