[PATCH] contracts: Stop relying on mangling for naming .pre/.post clones

["Arsen Arsenović" <arsen@aarsen.me>]

If the mangler is relied on, functions with extern "C" on them emit multiple
definitions of the same name.

gcc/cp/ChangeLog:

	* contracts.cc (build_contract_condition_function): Add pre/post
	suffixes to pre- and postcondition clones.
	* mangle.cc (write_encoding): Don't mangle pre- and postconditions.

gcc/testsuite/ChangeLog:

	* g++.dg/contracts/contracts-externC.C: New test.
---
Afternoon,

This change prevents contracts from emitting wrapper functions that have the
same name as the original function, by moving the logic that disambiguates them
from the mangler into the build_contract_condition_function helper.

Thanks, have nice day.

 gcc/cp/contracts.cc                           |  3 +++
 gcc/cp/mangle.cc                              |  7 -------
 .../g++.dg/contracts/contracts-externC.C      | 19 +++++++++++++++++++
 3 files changed, 22 insertions(+), 7 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/contracts/contracts-externC.C

diff --git a/gcc/cp/contracts.cc b/gcc/cp/contracts.cc
index 26316372389..f09eb87e283 100644
--- a/gcc/cp/contracts.cc
+++ b/gcc/cp/contracts.cc
@@ -161,6 +161,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-iterator.h"
 #include "print-tree.h"
 #include "stor-layout.h"
+#include "cgraph.h"
 
 const int max_custom_roles = 32;
 static contract_role contract_build_roles[max_custom_roles] = {
@@ -1451,6 +1452,8 @@ build_contract_condition_function (tree fndecl, bool pre)
     TREE_TYPE (fn) = build_method_type (class_type, TREE_TYPE (fn));
 
   DECL_NAME (fn) = copy_node (DECL_NAME (fn));
+  auto suffix = pre ? "pre" : "post";
+  SET_DECL_ASSEMBLER_NAME (fn, clone_function_name (fn, suffix));
   DECL_INITIAL (fn) = error_mark_node;
   DECL_ABSTRACT_ORIGIN (fn) = fndecl;
 
diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index e363ef35b9f..e97428e8f30 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -856,13 +856,6 @@ write_encoding (const tree decl)
 				mangle_return_type_p (decl),
 				d);
 
-      /* If this is the pre/post function for a guarded function, append
-	 .pre/post, like something from create_virtual_clone.  */
-      if (DECL_IS_PRE_FN_P (decl))
-	write_string (".pre");
-      else if (DECL_IS_POST_FN_P (decl))
-	write_string (".post");
-
       /* If this is a coroutine helper, then append an appropriate string to
 	 identify which.  */
       if (tree ramp = DECL_RAMP_FN (decl))
diff --git a/gcc/testsuite/g++.dg/contracts/contracts-externC.C b/gcc/testsuite/g++.dg/contracts/contracts-externC.C
new file mode 100644
index 00000000000..873056b742b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/contracts/contracts-externC.C
@@ -0,0 +1,19 @@
+// simple check to ensure we don't emit a function with the same name twice,
+// when wrapping functions in pre- and postconditions.
+// { dg-do link }
+// { dg-options "-std=c++2a -fcontracts -fcontract-continuation-mode=on" }
+
+volatile int x = 10;
+
+extern "C" void
+f ()
+  [[ pre: x < 10 ]]
+{
+}
+
+int
+main ()
+  [[ post: x > 10 ]]
+{
+  f();
+}
-- 
2.38.1