diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 56c63d8..eaa6d55 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -4026,6 +4026,9 @@ lookup_name_fuzzy (tree name, enum lookup_name_fuzzy_kind kind, location_t loc)
 						  IDENTIFIER_POINTER (name),
 						  header_hint));
 
+  bool name_reserved
+    = name_reserved_for_implementation_p (IDENTIFIER_POINTER (name));
+
   best_match<tree, tree> bm (name);
 
   /* Look within currently valid scopes.  */
@@ -4041,6 +4044,14 @@ lookup_name_fuzzy (tree name, enum lookup_name_fuzzy_kind kind, location_t loc)
 	if (TREE_CODE (binding->decl) == FUNCTION_DECL)
 	  if (C_DECL_IMPLICIT (binding->decl))
 	    continue;
+	/* Don't suggest names that are reserved for use by the
+	   implementation, unless NAME itself is reserved.  */
+	if (!name_reserved)
+	  {
+	    const char *suggestion_str = IDENTIFIER_POINTER (binding->id);
+	    if (name_reserved_for_implementation_p (suggestion_str))
+	      continue;
+	  }
 	switch (kind)
 	  {
 	  case FUZZY_LOOKUP_TYPENAME:
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 9f65c4d..f5581b7 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -5613,6 +5613,9 @@ consider_binding_level (tree name, best_match <tree, const char *> &bm,
 	  bm.consider (IDENTIFIER_POINTER (best_matching_field));
       }
 
+  bool name_reserved
+    = name_reserved_for_implementation_p (IDENTIFIER_POINTER (name));
+
   for (tree t = lvl->names; t; t = TREE_CHAIN (t))
     {
       tree d = t;
@@ -5633,10 +5636,23 @@ consider_binding_level (tree name, best_match <tree, const char *> &bm,
 	  && DECL_ANTICIPATED (d))
 	continue;
 
-      if (tree name = DECL_NAME (d))
-	/* Ignore internal names with spaces in them.  */
-	if (!strchr (IDENTIFIER_POINTER (name), ' '))
-	  bm.consider (IDENTIFIER_POINTER (name));
+      tree suggestion = DECL_NAME (d);
+      if (!suggestion)
+	continue;
+
+      const char *suggestion_str = IDENTIFIER_POINTER (suggestion);
+
+      /* Ignore internal names with spaces in them.  */
+      if (strchr (suggestion_str, ' '))
+	continue;
+
+      /* Don't suggest names that are reserved for use by the
+	 implementation, unless NAME itself is reserved.  */
+      if (name_reserved_for_implementation_p (suggestion_str)
+	  && !name_reserved)
+	continue;
+
+      bm.consider (suggestion_str);
     }
 }
 
diff --git a/gcc/spellcheck-tree.c b/gcc/spellcheck-tree.c
index 56740b9..310f8d2 100644
--- a/gcc/spellcheck-tree.c
+++ b/gcc/spellcheck-tree.c
@@ -66,6 +66,36 @@ find_closest_identifier (tree target, const auto_vec<tree> *candidates)
   return bm.get_best_meaningful_candidate ();
 }
 
+/* Return true iff STR begin with an underscore and either an uppercase
+   letter or another underscore, and is thus, for C and C++, reserved for
+   use by the implementation.  */
+
+bool
+name_reserved_for_implementation_p (const char *str)
+{
+  if (str[0] != '_')
+    return false;
+  return (str[1] == '_' || ISUPPER(str[1]));
+}
+
+/* Return true iff HASHNODE is a macro that should be offered as a
+   suggestion for a misspelling.  */
+
+static bool
+should_suggest_as_macro_p (cpp_hashnode *hashnode)
+{
+  if (hashnode->type != NT_MACRO)
+    return false;
+
+  /* Don't suggest names reserved for the implementation, but do suggest the builtin
+     macros such as __FILE__, __LINE__ etc.  */
+  if (name_reserved_for_implementation_p ((const char *)hashnode->ident.str)
+      && !(hashnode->flags & NODE_BUILTIN))
+    return false;
+
+  return true;
+}
+
 /* A callback for cpp_forall_identifiers, for use by best_macro_match's ctor.
    Process HASHNODE and update the best_macro_match instance pointed to be
    USER_DATA.  */
@@ -74,7 +104,7 @@ static int
 find_closest_macro_cpp_cb (cpp_reader *, cpp_hashnode *hashnode,
 			   void *user_data)
 {
-  if (hashnode->type != NT_MACRO)
+  if (!should_suggest_as_macro_p (hashnode))
     return 1;
 
   best_macro_match *bmm = (best_macro_match *)user_data;
@@ -131,12 +161,28 @@ test_find_closest_identifier ()
 				      &candidates));
 }
 
+/* Verify that name_reserved_for_implementation_p is sane.  */
+
+static void
+test_name_reserved_for_implementation_p ()
+{
+  ASSERT_FALSE (name_reserved_for_implementation_p (""));
+  ASSERT_FALSE (name_reserved_for_implementation_p ("foo"));
+  ASSERT_FALSE (name_reserved_for_implementation_p ("_"));
+  ASSERT_FALSE (name_reserved_for_implementation_p ("_foo"));
+  ASSERT_FALSE (name_reserved_for_implementation_p ("_42"));
+  ASSERT_TRUE (name_reserved_for_implementation_p ("_Foo"));
+  ASSERT_TRUE (name_reserved_for_implementation_p ("__"));
+  ASSERT_TRUE (name_reserved_for_implementation_p ("__foo"));
+}
+
 /* Run all of the selftests within this file.  */
 
 void
 spellcheck_tree_c_tests ()
 {
   test_find_closest_identifier ();
+  test_name_reserved_for_implementation_p ();
 }
 
 } // namespace selftest
diff --git a/gcc/spellcheck-tree.h b/gcc/spellcheck-tree.h
index eecfd1a..851ea22 100644
--- a/gcc/spellcheck-tree.h
+++ b/gcc/spellcheck-tree.h
@@ -74,4 +74,6 @@ class best_macro_match : public best_match<tree, cpp_hashnode *>
 		    cpp_reader *reader);
 };
 
+extern bool name_reserved_for_implementation_p (const char *str);
+
 #endif  /* GCC_SPELLCHECK_TREE_H  */
diff --git a/gcc/testsuite/c-c++-common/spellcheck-reserved.c b/gcc/testsuite/c-c++-common/spellcheck-reserved.c
new file mode 100644
index 0000000..08630ed
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/spellcheck-reserved.c
@@ -0,0 +1,35 @@
+/* Verify that we don't offer names that are reserved for the
+   implementation (PR c/83236).  */
+/* { dg-options "-nostdinc" } */
+
+/* Example of an identifier with a leading double-underscore.
+   We shouldn't offer '__ino_t' as a suggestion for an unknown 'ino_t'.  */
+
+typedef unsigned long int __ino_t;
+ino_t inode; /* { dg-error "did you mean 'int'" } */
+
+
+/* Example of a typedef with a leading double-underscore.  */
+
+typedef unsigned char __u_char;
+u_char ch; /* { dg-error "did you mean 'char'" } */
+
+
+/* Example of a macro with a leading double-underscore.  */
+
+# define __SOME_MACRO	int
+
+SOME_MACRO foo; /* { dg-bogus "__SOME_MACRO" } */
+/* { dg-error "'SOME_MACRO'" "" { target *-*-* } .-1 } */
+
+
+/* If the misspelled name itself matches the "reserved" pattern, then
+   it's OK to suggest such names.  */
+
+void test (const char *buf, char ch)
+{
+  __builtin_strtchr (buf, ch); /* { dg-line misspelled_reserved } */
+  /* { dg-warning "did you mean '__builtin_strchr'" "" { target c } misspelled_reserved } */
+  /* { dg-error "not declared"  "" { target c++ } misspelled_reserved } */
+  /* { dg-message "'__builtin_strrchr'"  "" { target c++ } misspelled_reserved } */
+}
