gccrs: proc_macro: Add from string implementation

Add a callback registration function into the proc macro library so the
compiler can register it's own lexing/parsing functions on load.

gcc/rust/ChangeLog:

	* expand/rust-proc-macro.cc (tokenstream_from_string): Add a
	function that creates a tokenstream from a given string.
	(load_macros_array): Add call to registration function.

libgrust/ChangeLog:

	* libproc_macro/proc_macro.cc (proc_macro_register_from_str):
	Add registration function.
	* libproc_macro/proc_macro.h (proc_macro_register_from_str):
	Add registration function prototype.
	* libproc_macro/tokenstream.cc (TokenStream::make_tokenstream):
	Add a new constructor from a string that uses the registered
	callback.
	(TokenStream__from_string): Add call to new constructor.
	* libproc_macro/tokenstream.h: Add registration
	declaration.
	* libproc_macro/registration.h: New file.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

5 files changed, 57 insertions, 2 deletions

diff --git a/libgrust/libproc_macro/proc_macro.cc b/libgrust/libproc_macro/proc_macro.cc
index 2e50f0afb01..effe7178b89 100644
--- a/libgrust/libproc_macro/proc_macro.cc
+++ b/libgrust/libproc_macro/proc_macro.cc
@@ -50,3 +50,5 @@ Procmacro::make_bang (const char *name, BangMacro macro)
 }
 
 } // namespace ProcMacro
+
+ProcMacro::from_str_function_t __gccrs_pm_callback_from_str_fn = nullptr;
diff --git a/libgrust/libproc_macro/proc_macro.h b/libgrust/libproc_macro/proc_macro.h
index 673f7a932f1..80dd28216af 100644
--- a/libgrust/libproc_macro/proc_macro.h
+++ b/libgrust/libproc_macro/proc_macro.h
@@ -30,6 +30,7 @@
 #include "group.h"
 #include "punct.h"
 #include "ident.h"
+#include "registration.h"
 
 namespace ProcMacro {
 
@@ -61,6 +62,9 @@ struct Bang
   const char *name;
   BangMacro macro;
 };
+
+void
+proc_macro_register_from_str (ProcMacro::from_str_function_t fn);
 }
 
 enum ProcmacroTag
diff --git a/libgrust/libproc_macro/registration.h b/libgrust/libproc_macro/registration.h
new file mode 100644
index 00000000000..bba69b1e9bc
--- /dev/null
+++ b/libgrust/libproc_macro/registration.h
@@ -0,0 +1,37 @@
+// Copyright (C) 2023 Free Software Foundation, Inc.
+//
+// This file is part of the GNU Proc Macro Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+#ifndef REGISTRATION_H
+#define REGISTRATION_H
+
+#include <string>
+#include "tokenstream.h"
+
+namespace ProcMacro {
+
+using from_str_function_t = ProcMacro::TokenStream (*) (std::string &, bool &);
+
+} // namespace ProcMacro
+
+extern "C" ProcMacro::from_str_function_t __gccrs_pm_callback_from_str_fn;
+
+#endif /* !REGISTRATION_H */
diff --git a/libgrust/libproc_macro/tokenstream.cc b/libgrust/libproc_macro/tokenstream.cc
index d1116fff7ee..c3502f1c7b7 100644
--- a/libgrust/libproc_macro/tokenstream.cc
+++ b/libgrust/libproc_macro/tokenstream.cc
@@ -22,6 +22,7 @@
 
 #include "tokenstream.h"
 #include "tokentree.h"
+#include "registration.h"
 
 #include <cstring>
 
@@ -45,6 +46,12 @@ TokenStream::make_tokenstream (std::uint64_t capacity)
   return {data, 0, capacity};
 }
 
+TokenStream
+TokenStream::make_tokenstream (std::string &source, bool &has_error)
+{
+  return __gccrs_pm_callback_from_str_fn (source, has_error);
+}
+
 void
 TokenStream::grow (std::uint64_t delta)
 {
@@ -99,8 +106,11 @@ extern "C" bool
 TokenStream__from_string (unsigned char *str, std::uint64_t len,
 			  TokenStream *ts)
 {
-  // FIXME: Implement using parser ?
-  return false;
+  bool result;
+  auto source = std::string (reinterpret_cast<const char *> (str), len);
+
+  *ts = TokenStream::make_tokenstream (source, result);
+  return result;
 }
 
 extern "C" TokenStream
diff --git a/libgrust/libproc_macro/tokenstream.h b/libgrust/libproc_macro/tokenstream.h
index 2c2231d5cda..8b2432b9a68 100644
--- a/libgrust/libproc_macro/tokenstream.h
+++ b/libgrust/libproc_macro/tokenstream.h
@@ -25,6 +25,7 @@
 
 #include <cstdint>
 #include <vector>
+#include <string>
 
 namespace ProcMacro {
 struct TokenTree;
@@ -43,6 +44,7 @@ public:
 
   static TokenStream make_tokenstream (std::vector<TokenTree> vec);
   static TokenStream make_tokenstream (std::uint64_t capacity = 1);
+  static TokenStream make_tokenstream (std::string &str, bool &has_error);
 
   static void drop (TokenStream *stream);
 };