gccrs: libgrust: Add format_parser library

Compile libformat_parser and link to it.

gcc/rust/ChangeLog:

	* Make-lang.in: Compile libformat_parser.
	* ast/rust-fmt.cc: New FFI definitions.
	* ast/rust-fmt.h: Likewise.
	* expand/rust-macro-builtins.cc (MacroBuiltin::format_args_handler): Call
	into libformat_parser.
	* expand/rust-macro-builtins.h: Define format_args!() handler proper.

libgrust/ChangeLog:

	* libformat_parser/Cargo.lock: New file.
	* libformat_parser/Cargo.toml: New file.
	* libformat_parser/generic_format_parser/Cargo.toml: New file.
	* libformat_parser/generic_format_parser/src/lib.rs: New file.
	* libformat_parser/src/bin.rs: New file.
	* libformat_parser/src/lib.rs: New file.

2 files changed, 48 insertions, 0 deletions

diff --git a/libgrust/libformat_parser/src/bin.rs b/libgrust/libformat_parser/src/bin.rs
new file mode 100644
index 00000000000..4b1f903ad5f
--- /dev/null
+++ b/libgrust/libformat_parser/src/bin.rs
@@ -0,0 +1,7 @@
+use libformat_parser::rust;
+
+fn main() {
+    dbg!(rust::collect_pieces(
+        std::env::args().nth(1).unwrap().as_str()
+    ));
+}
diff --git a/libgrust/libformat_parser/src/lib.rs b/libgrust/libformat_parser/src/lib.rs
new file mode 100644
index 00000000000..e6dc16eeb49
--- /dev/null
+++ b/libgrust/libformat_parser/src/lib.rs
@@ -0,0 +1,41 @@
+//! FFI interface for `rustc_format_parser`
+
+// what's the plan? Have a function return something that can be constructed into a vector?
+// or an iterator?
+
+use std::ffi::CStr;
+
+// TODO: Use rustc's version here #3
+use generic_format_parser::Piece;
+
+// FIXME: Rename?
+pub mod rust {
+    use generic_format_parser::{ParseMode, Parser, Piece};
+
+    pub fn collect_pieces(input: &str) -> Vec<Piece<'_>> {
+        // let parser = Parser::new();
+        let parser = Parser::new(input, None, None, true, ParseMode::Format);
+
+        parser.into_iter().collect()
+    }
+}
+
+#[repr(C)]
+pub struct PieceSlice {
+    base_ptr: *const Piece<'static /* FIXME: That's wrong */>,
+    len: usize,
+}
+
+#[no_mangle]
+pub extern "C" fn collect_pieces(input: *const libc::c_char) -> PieceSlice {
+    // FIXME: Add comment
+    let str = unsafe { CStr::from_ptr(input) };
+
+    // FIXME: No unwrap
+    let pieces = rust::collect_pieces(str.to_str().unwrap());
+
+    PieceSlice {
+        base_ptr: pieces.as_ptr(),
+        len: pieces.len(),
+    }
+}