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.

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

diff --git a/gcc/rust/expand/rust-proc-macro.cc b/gcc/rust/expand/rust-proc-macro.cc
index 2fdfcb20b19b9e5ef26851d23897da68b482a0df..3865b87b75b28a4070856227725e66cb7eb7eebd 100644 (file)
--- a/gcc/rust/expand/rust-proc-macro.cc
+++ b/gcc/rust/expand/rust-proc-macro.cc
@@ -45,8 +45,6 @@ CustomDeriveProcMacro::CustomDeriveProcMacro (ProcMacro::CustomDerive macro)
     macro (macro.macro)
 {}
 
-const std::string PROC_MACRO_DECL_PREFIX = "__gccrs_proc_macro_decls_";
-
 namespace {
 
 ProcMacro::Literal
@@ -150,8 +148,10 @@ 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 +175,19 @@ load_macros (std::string path)
                                            array->macros + array->length);
 }
 
+std::string
+generate_proc_macro_decls_symbol (std::uint32_t stable_crate_id)
+{
+#define PROC_MACRO_DECLS_FMT_ARGS                                              \
+  "__gccrs_proc_macro_decls_%08x__", stable_crate_id
+  // Size could be hardcoded since we know the input size but I elected to
+  // calculate it everytime so we won't have any desync between code and data.
+  int size = std::snprintf (nullptr, 0, PROC_MACRO_DECLS_FMT_ARGS);
+  std::vector<char> buf (size + 1);
+  std::sprintf (buf.data (), PROC_MACRO_DECLS_FMT_ARGS);
+#undef PROC_MACRO_DECLS_FMT_ARGS
+
+  return std::string (buf.cbegin (), buf.cend ());
+}
+
 } // namespace Rust

diff --git a/gcc/rust/expand/rust-proc-macro.h b/gcc/rust/expand/rust-proc-macro.h
index d994ed9bf5e080bd91d9586b19a1566e2f81ad2c..6ffaaf6c099f7447484bbb5a6acc0f6d2b2870ab 100644 (file)
--- a/gcc/rust/expand/rust-proc-macro.h
+++ b/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 */