ICE gcc_jit_context_new_function name contains invalid character: ''

struct root_ns1_A;
struct root_ns2_B;
extern "C" {
    #[link_name = "\u{1}_ZN4root3ns21B1fERKNS_3ns11AE"]
    fn root_ns2_B_f(this: *mut root_ns2_B, a: *mut root_ns1_A);
}
impl root_ns2_B {
    unsafe fn f(&mut self, a: *mut root_ns1_A) {
        root_ns2_B_f(self, a)
    }
}

-Zcodegen-backend=gcc -Clink-dead-code=true --crate-type=lib

warning: type `root_ns1_A` should have an upper camel case name
 --> a.rs:1:8
  |
1 | struct root_ns1_A;
  |        ^^^^^^^^^^ help: convert the identifier to upper camel case: `RootNs1A`
  |
  = note: `#[warn(non_camel_case_types)]` (part of `#[warn(nonstandard_style)]`) on by default

warning: type `root_ns2_B` should have an upper camel case name
 --> a.rs:2:8
  |
2 | struct root_ns2_B;
  |        ^^^^^^^^^^ help: convert the identifier to upper camel case: `RootNs2B`

warning: struct `root_ns1_A` is never constructed
 --> a.rs:1:8
  |
1 | struct root_ns1_A;
  |        ^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default

warning: struct `root_ns2_B` is never constructed
 --> a.rs:2:8
  |
2 | struct root_ns2_B;
  |        ^^^^^^^^^^

warning: method `f` is never used
 --> a.rs:8:15
  |
7 | impl root_ns2_B {
  | --------------- method in this implementation
8 |     unsafe fn f(&mut self, a: *mut root_ns1_A) {
  |               ^

warning: function `root_ns2_B_f` is never used
 --> a.rs:5:8
  |
5 |     fn root_ns2_B_f(this: *mut root_ns2_B, a: *mut root_ns1_A);
  |        ^^^^^^^^^^^^

warning: `extern` block uses type `root_ns2_B`, which is not FFI-safe
 --> a.rs:5:27
  |
5 |     fn root_ns2_B_f(this: *mut root_ns2_B, a: *mut root_ns1_A);
  |                           ^^^^^^^^^^^^^^^ not FFI-safe
  |
  = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
  = note: this struct has unspecified layout
note: the type is defined here
 --> a.rs:2:1
  |
2 | struct root_ns2_B;
  | ^^^^^^^^^^^^^^^^^
  = note: `#[warn(improper_ctypes)]` on by default

warning: `extern` block uses type `root_ns1_A`, which is not FFI-safe
 --> a.rs:5:47
  |
5 |     fn root_ns2_B_f(this: *mut root_ns2_B, a: *mut root_ns1_A);
  |                                               ^^^^^^^^^^^^^^^ not FFI-safe
  |
  = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
  = note: this struct has unspecified layout
note: the type is defined here
 --> a.rs:1:1
  |
1 | struct root_ns1_A;
  | ^^^^^^^^^^^^^^^^^

libgccjit.so: error: : gcc_jit_context_new_function: name "_ZN4root3ns21B1fERKNS_3ns11AE" contains invalid character: ''
gcc_jit_function_get_address: NULL function
gcc_jit_function_get_param_count: NULL function
gcc_jit_function_get_return_type: NULL function_type
libgccjit.so: error: : gcc_jit_function_new_local: NULL type
libgccjit.so: error: : gcc_jit_context_new_call: NULL function
libgccjit.so: error: : gcc_jit_block_add_assignment: NULL lvalue
gcc_jit_lvalue_as_rvalue: NULL lvalue
error: failed to build archive at `liba.rlib`: failed to open object file: No such file or directory (os error 2)

error: aborting due to 1 previous error; 8 warnings emitted

Re-run the supplied a.rs reproducer with -Zcodegen-backend=gcc -Clink-dead-code=true --crate-type=lib, then start at gcc_jit_context_new_function and the reported invalid mangled name. Done means the reproducer no longer triggers the ICE or archive-build failure and the crate compiles successfully.