[COMMITTED] algol68: introduce _libga68_unreachable and use it in unions

[Jose E. Marchesi]

---
 gcc/algol68/a68-low-coercions.cc | 14 +++++++++++++-
 gcc/algol68/a68-low-runtime.def  |  5 +++--
 libga68/ga68-error.c             |  9 +++++++++
 libga68/ga68.h                   |  1 +
 4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/gcc/algol68/a68-low-coercions.cc b/gcc/algol68/a68-low-coercions.cc
index 4464397784c..b9e1acee9ce 100644
--- a/gcc/algol68/a68-low-coercions.cc
+++ b/gcc/algol68/a68-low-coercions.cc
@@ -115,7 +115,19 @@ a68_lower_uniting (NODE_T *p, LOW_CTX_T ctx)
 	      field_index += 1;
 	    }
 
-	  // XXX emit run-time error: this should not be reached.
+	  /* This should not be reached.  Emit run-time error.  */
+	  {
+	    unsigned int lineno = NUMBER (LINE (INFO (p)));
+	    const char *filename_str = FILENAME (LINE (INFO (p)));
+	    tree filename = build_string_literal (strlen (filename_str) + 1,
+						  filename_str);
+	    tree call = a68_build_libcall (A68_LIBCALL_UNREACHABLE,
+					   void_type_node, 2,
+					   filename,
+					   build_int_cst (unsigned_type_node, lineno));
+	    a68_add_stmt (call);
+	  }
+
 	  a68_add_stmt (build1 (LABEL_EXPR, void_type_node, done_label));
 	  a68_add_stmt (rows);
 	  return a68_pop_range ();
diff --git a/gcc/algol68/a68-low-runtime.def b/gcc/algol68/a68-low-runtime.def
index 443884425c5..86c85e28bc4 100644
--- a/gcc/algol68/a68-low-runtime.def
+++ b/gcc/algol68/a68-low-runtime.def
@@ -41,8 +41,9 @@ along with GCC; see the file COPYING3.  If not see
 
 DEF_A68_RUNTIME (ASSERT, "_libga68_assert", RT(VOID), P2(CONSTCHARPTR, UINT), ECF_NORETURN)
 DEF_A68_RUNTIME (MALLOC, "_libga68_malloc", RT(VOIDPTR), P1(SIZE), ECF_NOTHROW | ECF_LEAF)
-DEF_A68_RUNTIME (DEREFNIL, "_libga68_derefnil", RT(VOID), P2(CONSTCHARPTR, UINT), 0)
-DEF_A68_RUNTIME (BITSBOUNDSERROR, "_libga68_bitsboundserror", RT(VOID), P3(CONSTCHARPTR,UINT,INT), 0)
+DEF_A68_RUNTIME (DEREFNIL, "_libga68_derefnil", RT(VOID), P2(CONSTCHARPTR, UINT), ECF_NORETURN)
+DEF_A68_RUNTIME (UNREACHABLE, "_libga68_unreachable", RT(VOID), P2(CONSTCHARPTR, UINT), ECF_NORETURN)
+DEF_A68_RUNTIME (BITSBOUNDSERROR, "_libga68_bitsboundserror", RT(VOID), P3(CONSTCHARPTR,UINT,INT), ECF_NORETURN)
 DEF_A68_RUNTIME (ARRAYBOUNDS, "_libga68_bounds", RT(VOID),
 		 P5(CONSTCHARPTR, UINT, INT, INT, INT), ECF_NORETURN)
 DEF_A68_RUNTIME (RANDOM, "_libga68_random", RT(FLOAT), P0(), 0)
diff --git a/libga68/ga68-error.c b/libga68/ga68-error.c
index 9cee47e3c0d..317d99fdf4d 100644
--- a/libga68/ga68-error.c
+++ b/libga68/ga68-error.c
@@ -66,6 +66,15 @@ _libga68_bitsboundserror (const char *filename, unsigned int lineno,
 		  pos, filename, lineno);
 }
 
+/* Unreachable error.  */
+
+void
+_libga68_unreachable (const char *filename, unsigned int lineno)
+{
+  _libga68_abort ("run-time error: unreachable reached at %s:%d\n",
+		  filename, lineno);
+}
+
 /* Bounds failure.  */
 
 void
diff --git a/libga68/ga68.h b/libga68/ga68.h
index 41657b8321a..076787b722a 100644
--- a/libga68/ga68.h
+++ b/libga68/ga68.h
@@ -38,6 +38,7 @@ void _libga68_assert (const char *filename, unsigned int lineno);
 void _libga68_derefnil (const char *filename, unsigned int lineno);
 void _libga68_bitsboundserror (const char *filename, unsigned int lineno,
 			       ssize_t pos);
+void _libga68_unreachable (const char *filename, unsigned int lineno);
 void _libga68_bounds (const char *filename, unsigned int lineno,
 		      ssize_t index, ssize_t lower_bound, ssize_t upper_bound);
 
-- 
2.30.2