gccrs: Change proc macro entrypoint

Change proc macro entrypoint from a fixed constant declaration to a
proper generation from the stable crate id. Although the stable crate id
is not in use yet, the mechanism to handle it is.

gcc/rust/ChangeLog:

	* expand/rust-proc-macro.cc (CustomDeriveProcMacro::CustomDeriveProcMacro):
	Remove constant string declaration.
	(load_macros_array): Add call to the new generation function.
	(generate_proc_macro_decls_symbol): Add a new function to generate the
	entrypoint symbol name from the stable crate id.
	(PROC_MACRO_DECLS_FMT_ARGS):
	New macro to keep formats arguments in sync between each call.
	* expand/rust-proc-macro.h (generate_proc_macro_decls_symbol): Add
	function prototype.
	* rust-system.h: Include <iomanip>.

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

gcc/rust/expand/rust-proc-macro.cc

@@ -14,12 +14,14 @@
 // along with GCC; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
+#include "rust-system.h"
 #include "rust-diagnostics.h"
 #include "rust-proc-macro.h"
 #include "rust-session-manager.h"
 #include "rust-lex.h"
 #include "rust-token-converter.h"
 #include "rust-attributes.h"
+
 #ifndef _WIN32
 #include <dlfcn.h>
 #endif
@@ -45,8 +47,6 @@ CustomDeriveProcMacro::CustomDeriveProcMacro (ProcMacro::CustomDerive macro)
     macro (macro.macro)
 {}
 
-const std::string PROC_MACRO_DECL_PREFIX = "__gccrs_proc_macro_decls_";
-
 namespace {
 
 ProcMacro::Literal
@@ -150,8 +150,10 @@ load_macros_array (std::string path)
 
   // FIXME: Add CrateStableId handling, right now all versions may be loaded,
   // even incompatible ones.
+  auto symbol_name = generate_proc_macro_decls_symbol (0 /* FIXME */);
+
   return *reinterpret_cast<const ProcMacro::ProcmacroArray **> (
-    dlsym (handle, PROC_MACRO_DECL_PREFIX.c_str ()));
+    dlsym (handle, symbol_name.c_str ()));
 #else
   rust_sorry_at (UNDEF_LOCATION,
 		 "Procedural macros are not yet supported on windows host");
@@ -175,4 +177,14 @@ load_macros (std::string path)
 					    array->macros + array->length);
 }
 
+std::string
+generate_proc_macro_decls_symbol (std::uint32_t stable_crate_id)
+{
+  std::ostringstream stream;
+  stream << "__gccrs_proc_macro_decls_" << std::setfill ('0') << std::hex
+	 << std::setw (8) << stable_crate_id << "__";
+
+  return stream.str ();
+}
+
 } // namespace Rust

gcc/rust/expand/rust-proc-macro.h

@@ -85,6 +85,9 @@ public:
 const std::vector<ProcMacro::Procmacro>
 load_macros (std::string path);
 
+std::string
+generate_proc_macro_decls_symbol (std::uint32_t stable_crate_id);
+
 } // namespace Rust
 
 #endif /* ! RUST_PROC_MACRO_H */

gcc/rust/rust-system.h

@@ -54,6 +54,7 @@
  * before the macro magic of safe-ctype.h, which is included by
  * system.h. */
 #include <iostream>
+#include <iomanip>
 
 #include "system.h"
 #include "ansidecl.h"