3 files changed, 54 insertions, 0 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 2b63689..cb3b9cf 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,9 @@
+2019-10-14  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* c-common.h (user_facing_original_type_p): Declare.
+	* c-common.c: Include c-spellcheck.h.
+	(user_facing_original_type_p): New function.
+
 2019-10-12  Jakub Jelinek  <jakub@redhat.com>
 
 	* c-common.h (c_omp_mark_declare_variant,
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 909f52a..483d874 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -48,6 +48,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify.h"
 #include "substring-locations.h"
 #include "spellcheck.h"
+#include "c-spellcheck.h"
 #include "selftest.h"
 
 cpp_reader *parse_in;		/* Declared in c-pragma.h.  */
@@ -7713,6 +7714,52 @@ set_underlying_type (tree x)
     }
 }
 
+/* Return true if it is worth exposing the DECL_ORIGINAL_TYPE of TYPE to
+   the user in diagnostics, false if it would be better to use TYPE itself.
+   TYPE is known to satisfy typedef_variant_p.  */
+
+bool
+user_facing_original_type_p (const_tree type)
+{
+  gcc_assert (typedef_variant_p (type));
+  tree decl = TYPE_NAME (type);
+
+  /* Look through any typedef in "user" code.  */
+  if (!DECL_IN_SYSTEM_HEADER (decl) && !DECL_IS_BUILTIN (decl))
+    return true;
+
+  /* If the original type is also named and is in the user namespace,
+     assume it too is a user-facing type.  */
+  tree orig_type = DECL_ORIGINAL_TYPE (decl);
+  if (tree orig_id = TYPE_IDENTIFIER (orig_type))
+    if (!name_reserved_for_implementation_p (IDENTIFIER_POINTER (orig_id)))
+      return true;
+
+  switch (TREE_CODE (orig_type))
+    {
+    /* Don't look through to an anonymous vector type, since the syntax
+       we use for them in diagnostics isn't real C or C++ syntax.
+       And if ORIG_TYPE is named but in the implementation namespace,
+       TYPE is likely to be more meaningful to the user.  */
+    case VECTOR_TYPE:
+      return false;
+
+    /* Don't expose anonymous tag types that are presumably meant to be
+       known by their typedef name.  Also don't expose tags that are in
+       the implementation namespace, such as:
+
+         typedef struct __foo foo;  */
+    case RECORD_TYPE:
+    case UNION_TYPE:
+    case ENUMERAL_TYPE:
+      return false;
+
+    /* Look through to anything else.  */
+    default:
+      return true;
+    }
+}
+
 /* Record the types used by the current global variable declaration
    being parsed, so that we can decide later to emit their debug info.
    Those types are in types_used_by_cur_var_decl, and we are going to
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index db7f26e..3bc021b 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1063,6 +1063,7 @@ extern tree builtin_type_for_size (int, bool);
 extern void c_common_mark_addressable_vec (tree);
 
 extern void set_underlying_type (tree);
+extern bool user_facing_original_type_p (const_tree);
 extern void record_types_used_by_current_var_decl (tree);
 extern vec<tree, va_gc> *make_tree_vector (void);
 extern void release_tree_vector (vec<tree, va_gc> *);