c++/contracts: ICE in C++ Contracts with '-fno-exceptions' [PR 110159]

We currently only initialise terminate_fn if exceptions are enabled.
However, contract handling requires terminate_fn when building the
contract because a contract failure may result in std::terminate call
regardless of whether the exceptions are enabled. Refactored
init_exception_processing to extract the initialisation of
terminate_fn. New function init_terminate_fn added that initialises
terminate_fn if it hasn't already been initialised. Call to terminate_fn
added in cxx_init_decl_processing if contracts are enabled.

	PR c++/110159

gcc/cp/ChangeLog:

	* cp-tree.h (init_terminate_fn): Declaration of a new function.
	* decl.cc (cxx_init_decl_processing): If contracts are enabled,
	call init_terminate_fn.
	* except.cc (init_exception_processing): Function refactored to
	call init_terminate_fn.
	(init_terminate_fn): Added new function that initializes
	terminate_fn if	it hasn't already been initialised.

gcc/testsuite/ChangeLog:

	* g++.dg/contracts/pr110159.C: New test.

Signed-off-by: Nina Ranns <dinka.ranns@gmail.com>

gcc/cp/cp-tree.h

@@ -7194,6 +7194,7 @@ extern void qualified_name_lookup_error		(tree, tree, tree,
 						 location_t);
 
 /* in except.cc */
+extern void init_terminate_fn			(void);
 extern void init_exception_processing		(void);
 extern tree expand_start_catch_block		(tree);
 extern void expand_end_catch_block		(void);

gcc/cp/decl.cc

@@ -5172,6 +5172,9 @@ cxx_init_decl_processing (void)
   if (flag_exceptions)
     init_exception_processing ();
 
+  if (flag_contracts)
+    init_terminate_fn ();
+
   if (modules_p ())
     init_modules (parse_in);
 

gcc/cp/except.cc

@@ -42,6 +42,28 @@ static tree wrap_cleanups_r (tree *, int *, void *);
 static bool is_admissible_throw_operand_or_catch_parameter (tree, bool,
 							    tsubst_flags_t);
 
+/* Initializes the node to std::terminate, which is used in exception
+  handling and contract handling.  */
+
+void
+init_terminate_fn (void)
+{
+  if (terminate_fn)
+    return;
+
+  tree tmp;
+
+  push_nested_namespace (std_node);
+  tmp = build_function_type_list (void_type_node, NULL_TREE);
+  terminate_fn = build_cp_library_fn_ptr ("terminate", tmp,
+					   ECF_NOTHROW | ECF_NORETURN
+					   | ECF_COLD);
+  gcc_checking_assert (TREE_THIS_VOLATILE (terminate_fn)
+		       && TREE_NOTHROW (terminate_fn));
+  pop_nested_namespace (std_node);
+
+}
+
 /* Sets up all the global eh stuff that needs to be initialized at the
    start of compilation.  */
 
@@ -51,14 +73,7 @@ init_exception_processing (void)
   tree tmp;
 
   /* void std::terminate (); */
-  push_nested_namespace (std_node);
-  tmp = build_function_type_list (void_type_node, NULL_TREE);
-  terminate_fn = build_cp_library_fn_ptr ("terminate", tmp,
-					   ECF_NOTHROW | ECF_NORETURN
-					   | ECF_COLD);
-  gcc_checking_assert (TREE_THIS_VOLATILE (terminate_fn)
-		       && TREE_NOTHROW (terminate_fn));
-  pop_nested_namespace (std_node);
+  init_terminate_fn ();
 
   /* void __cxa_call_unexpected(void *); */
   tmp = build_function_type_list (void_type_node, ptr_type_node, NULL_TREE);

gcc/testsuite/g++.dg/contracts/pr110159.C

@@ -0,0 +1,27 @@
+// check that contracts can be handled even when exceptions are disabled
+// { dg-do run }
+// { dg-options "-std=c++2a -fcontracts -fno-exceptions " }
+// { dg-output "contract violation in function f at .* a<5" }
+
+#include <exception>
+#include <cstdlib>
+
+int terminate_called = 0;
+void my_term()
+{
+    std::exit(0);
+}
+
+
+void f(int a)
+  [[ pre : a<5 ]]
+  {
+  }
+
+int
+main ()
+{
+  std::set_terminate (my_term);
+  f(3);
+  f(10);
+}