[gcc/devel/rust/master] libproc_macro: Add is_available ffi

[gcc/devel/rust/master] libproc_macro: Add is_available ffi

[Thomas Schwinge]

https://gcc.gnu.org/g:eedfefb49d1aa8750c52a4893149207cc6ba5dbc

commit eedfefb49d1aa8750c52a4893149207cc6ba5dbc
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Thu Feb 16 18:35:24 2023 +0100

    libproc_macro: Add is_available ffi
    
    Add ffi call for is_available function.
    
    ChangeLog:
    
            * librust/proc_macro/rust/bridge.rs: Add internal
            implementation.
            * librust/proc_macro/rust/lib.rs: Add call to internal
            implementation.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 librust/proc_macro/rust/bridge.rs | 8 ++++++++
 librust/proc_macro/rust/lib.rs    | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/librust/proc_macro/rust/bridge.rs b/librust/proc_macro/rust/bridge.rs
index eb49071fb1f..ff2c49688b6 100644
--- a/librust/proc_macro/rust/bridge.rs
+++ b/librust/proc_macro/rust/bridge.rs
@@ -2,3 +2,11 @@ pub mod ident;
 pub mod literal;
 pub mod punct;
 pub mod span;
+
+extern "C" {
+    fn bridge__is_available() -> bool;
+}
+
+pub fn is_available() -> bool {
+    unsafe { bridge__is_available() }
+}
diff --git a/librust/proc_macro/rust/lib.rs b/librust/proc_macro/rust/lib.rs
index 48e1bcd7679..4e6802abeda 100644
--- a/librust/proc_macro/rust/lib.rs
+++ b/librust/proc_macro/rust/lib.rs
@@ -22,7 +22,7 @@ pub mod token_stream;
 /// This function provide a non panicking way to detect whether the API is
 /// invoked from inside of a procedural macro.
 pub fn is_available() -> bool {
-    todo!("Implement this function")
+    bridge::is_available()
 }
 
 /// A single token or a delimited sequence of token trees.