diff mbox series

C/C++: more stdlib header hints (PR c/81404)

Message ID 1508261630-13799-1-git-send-email-dmalcolm@redhat.com
State New
Headers show
Series C/C++: more stdlib header hints (PR c/81404) | expand

Commit Message

David Malcolm Oct. 17, 2017, 5:33 p.m. UTC 
This patch depends on:

* "[PATCH] c-family: add name_hint/deferred_diagnostic (v2)"
  * https://gcc.gnu.org/ml/gcc-patches/2017-10/msg01021.html
  (waiting review)

* [PATCH 3/3] C: hints for missing stdlib includes for macros and types
  * https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00125.html
  (approved, pending the prereq above)

It extends the C frontend's "knowledge" of the C stdlib within
get_c_name_hint to cover some more macros and functions, covering
a case reported in PR c/81404 ("INT_MAX"), so that rather than printing:

  t.c:5:12: error: 'INT_MAX' undeclared here (not in a function); did you mean '__INT_MAX__'?
   int test = INT_MAX;
              ^~~~~~~
              __INT_MAX__

we instead print:

  t.c:5:12: error: 'INT_MAX' undeclared here (not in a function)
   int test = INT_MAX;
              ^~~~~~~
  t.c:5:12: note: 'INT_MAX' is defined in header '<limits.h>'; did you forget to '#include <limits.h>'?
  t.c:1:1:
  +#include <limits.h>
 
  t.c:5:12:
   int test = INT_MAX;
              ^~~~~~~

It also adds generalizes some of the code for this (and for the "std::"
namespace hints in the C++ frontend), moving it to a new
c-family/known-headers.cc and .h, and introducing a class known_headers.
This currently just works by scanning a hardcoded array of known
name/header associations, but perhaps in the future could be turned
into some kind of symbol database so that the compiler could record API
uses and use that to offer suggestions e.g.

foo.cc: error: 'myapi::foo' was not declared in this scope
foo.cc: note: 'myapi::foo" was declared in header 'myapi/private.h'
(included via 'myapi/public.h') when compiling 'bar.cc'; did you forget to
'#include "myapi/public.h"'?

or somesuch.

In any case, moving this to a class gives an easier way to locate the
hardcoded knowledge about the stdlib.

The patch also adds similar code to the C++ frontend covering
unqualified names in the standard library, so that rather than just
e.g.:

 t.cc:19:13: error: 'NULL' was not declared in this scope
  void *ptr = NULL;
              ^~~~

we can emit:

 t.cc:19:13: error: 'NULL' was not declared in this scope
  void *ptr = NULL;
              ^~~~
 t.cc:19:13: note: 'NULL' is defined in header '<cstddef>'; did you forget
 to '#include <cstddef>'?
 t.cc:1:1:
 +#include <cstddef>

 t.cc:19:13:
   void *ptr = NULL;
               ^~~~

(Also XFAIL for PR c++/80567 added for the C++ testcase; this is a
separate pre-existing bug exposed by the testcase for PR 81404).

Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.

OK for trunk once the prereqs are in place?

gcc/ChangeLog:
	* Makefile.in (C_COMMON_OBJS): Add c-family/known-headers.o.

gcc/c-family/ChangeLog:
	* known-headers.cc: New file, with suggest_missing_header taken
	from c/c-decl.c.
	* known-headers.h: Likewise.

gcc/c/ChangeLog:
	PR c/81404
	* c-decl.c: Include "c-family/known-headers.h".
	(get_c_name_hint): Reimplement in terms of the API in
	known-headers.h.  Add some knowledge about <limits.h>,
	<stdint.h>, and <wchar.h>.
	(class suggest_missing_header): Move to known-header.h.

gcc/cp/ChangeLog:
	* name-lookup.c: Include "c-family/known-headers.h".
	(get_std_name_hint): Reimplement in terms of the API in
	known-headers.h.
	(get_stdlib_name_hint): New function.
	(lookup_name_fuzzy): Call get_stdlib_name_hint.

gcc/testsuite/ChangeLog:
	PR c/81404
	PR c++/80567
	* g++.dg/spellcheck-stdlib.C: New test case.
	* gcc.dg/spellcheck-stdlib.c (test_INT_MAX): New.
---
 gcc/Makefile.in                          |  2 +-
 gcc/c-family/known-headers.cc            | 68 ++++++++++++++++++++++++
 gcc/c-family/known-headers.h             | 63 ++++++++++++++++++++++
 gcc/c/c-decl.c                           | 84 ++++++++++++++----------------
 gcc/cp/name-lookup.c                     | 89 +++++++++++++++++++++++++++-----
 gcc/testsuite/g++.dg/spellcheck-stdlib.C | 84 ++++++++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/spellcheck-stdlib.c |  9 ++++
 7 files changed, 341 insertions(+), 58 deletions(-)
 create mode 100644 gcc/c-family/known-headers.cc
 create mode 100644 gcc/c-family/known-headers.h
 create mode 100644 gcc/testsuite/g++.dg/spellcheck-stdlib.C

Comments

Joseph Myers Oct. 17, 2017, 8:05 p.m. UTC | #1 
On Tue, 17 Oct 2017, David Malcolm wrote:

> It also adds generalizes some of the code for this (and for the "std::"
> namespace hints in the C++ frontend), moving it to a new
> c-family/known-headers.cc and .h, and introducing a class known_headers.
> This currently just works by scanning a hardcoded array of known
> name/header associations, but perhaps in the future could be turned
> into some kind of symbol database so that the compiler could record API
> uses and use that to offer suggestions e.g.
> 
> foo.cc: error: 'myapi::foo' was not declared in this scope
> foo.cc: note: 'myapi::foo" was declared in header 'myapi/private.h'
> (included via 'myapi/public.h') when compiling 'bar.cc'; did you forget to
> '#include "myapi/public.h"'?
> 
> or somesuch.
> 
> In any case, moving this to a class gives an easier way to locate the
> hardcoded knowledge about the stdlib.
> 
> The patch also adds similar code to the C++ frontend covering
> unqualified names in the standard library, so that rather than just

I'd tend to expect hardcoded standard library knowledge, where it relates 
to symbols present for both C and C++, to be in a common c-family file 
(e.g. listing both C and C++ headers for each symbol, with the possibility 
of some symbols only having a header listed for one C and C++; most C 
symbols would have <foo.h> and <cfoo> listed, but some might be different, 
e.g. wchar_t being a keyword in C++ or clog being completely different in 
the two libraries).  That reduces the chance of a symbol being 
gratuitously listed for one language only when such hints make sense for 
it in both languages.
Martin Sebor Oct. 18, 2017, 2:09 a.m. UTC | #2 
On 10/17/2017 11:33 AM, David Malcolm wrote:
> This patch depends on:
>
> * "[PATCH] c-family: add name_hint/deferred_diagnostic (v2)"
>   * https://gcc.gnu.org/ml/gcc-patches/2017-10/msg01021.html
>   (waiting review)
>
> * [PATCH 3/3] C: hints for missing stdlib includes for macros and types
>   * https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00125.html
>   (approved, pending the prereq above)
>
> It extends the C frontend's "knowledge" of the C stdlib within
> get_c_name_hint to cover some more macros and functions, covering
> a case reported in PR c/81404 ("INT_MAX"), so that rather than printing:
>
>   t.c:5:12: error: 'INT_MAX' undeclared here (not in a function); did you mean '__INT_MAX__'?
>    int test = INT_MAX;
>               ^~~~~~~
>               __INT_MAX__
>
> we instead print:
>
>   t.c:5:12: error: 'INT_MAX' undeclared here (not in a function)
>    int test = INT_MAX;
>               ^~~~~~~
>   t.c:5:12: note: 'INT_MAX' is defined in header '<limits.h>'; did you forget to '#include <limits.h>'?
>   t.c:1:1:
>   +#include <limits.h>
>
>   t.c:5:12:
>    int test = INT_MAX;
>               ^~~~~~~
>
> It also adds generalizes some of the code for this (and for the "std::"
> namespace hints in the C++ frontend), moving it to a new
> c-family/known-headers.cc and .h, and introducing a class known_headers.
> This currently just works by scanning a hardcoded array of known
> name/header associations, but perhaps in the future could be turned
> into some kind of symbol database so that the compiler could record API
> uses and use that to offer suggestions e.g.

I think this feature will be especially helpful for the not
so common symbols or those that are often expected to be
declared in the wrong header.  As you say, the data structure
can be improved/enhanced and made more general.  Until that
happens, it would be great to complete the set of the standard
symbols.  Since the full list is going to be quite long, it
might be worthwhile to sort it so it can be searched using
a binary search.

Btw., while on the subject of enhancements, I think it would
also be helpful to make the preprocessor aware of the set of
predefined macros and have it issue warnings in cases where
they are either used in nonsensical or error-prone ways.  One
example that I've had trouble with is making mistakes testing
the C++ __cplusplus macro for equality that can never be true,
as in the contrived:

   #if __cplusplus == 2014
   // C++ 14 code
   #else
   // other code
   #endif

(The real problems usually involve several non-trivial tests
not all of which get tested.)

Martin
diff mbox series

Patch

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 2809619..9855919 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -1190,7 +1190,7 @@  C_COMMON_OBJS = c-family/c-common.o c-family/c-cppbuiltin.o c-family/c-dump.o \
   c-family/c-semantics.o c-family/c-ada-spec.o \
   c-family/c-cilkplus.o \
   c-family/array-notation-common.o c-family/cilk.o c-family/c-ubsan.o \
-  c-family/c-attribs.o c-family/c-warn.o
+  c-family/c-attribs.o c-family/c-warn.o c-family/known-headers.o
 
 # Language-independent object files.
 # We put the *-match.o and insn-*.o files first so that a parallel make
diff --git a/gcc/c-family/known-headers.cc b/gcc/c-family/known-headers.cc
new file mode 100644
index 0000000..008788e
--- /dev/null
+++ b/gcc/c-family/known-headers.cc
@@ -0,0 +1,68 @@ 
+/* Support for suggestions about missing #include directives.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "c-family/c-common.h"
+#include "c-family/known-headers.h"
+#include "gcc-rich-location.h"
+
+/* Given NAME, attempt to locate a header that would declare it,
+   or return NULL if we don't know of such a header.  */
+
+const char *
+known_headers::get_header_for_name (const char *name) const
+{
+  gcc_assert (name);
+
+  for (size_t i = 0; i < m_num_hints; i++)
+    if (0 == strcmp (name, m_hints[i].name))
+	return m_hints[i].header;
+
+  return NULL;
+}
+
+/* Implementation of class suggest_missing_header.  */
+
+/* suggest_missing_header's ctor.  */
+
+suggest_missing_header::suggest_missing_header (location_t loc,
+						const char *name,
+						const char *header_hint)
+: deferred_diagnostic (loc), m_name_str (name), m_header_hint (header_hint)
+{
+  gcc_assert (name);
+  gcc_assert (header_hint);
+}
+
+/* suggest_missing_header's dtor.  */
+
+suggest_missing_header::~suggest_missing_header ()
+{
+  if (is_suppressed_p ())
+    return;
+
+  gcc_rich_location richloc (get_location ());
+  maybe_add_include_fixit (&richloc, m_header_hint);
+  inform_at_rich_loc (&richloc,
+		      "%qs is defined in header %qs;"
+		      " did you forget to %<#include %s%>?",
+		      m_name_str, m_header_hint, m_header_hint);
+}
diff --git a/gcc/c-family/known-headers.h b/gcc/c-family/known-headers.h
new file mode 100644
index 0000000..11057c8
--- /dev/null
+++ b/gcc/c-family/known-headers.h
@@ -0,0 +1,63 @@ 
+/* Support for suggestions about missing #include directives.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_KNOWN_HEADERS_H
+#define GCC_KNOWN_HEADERS_H
+
+/* A struct for associating names in a standard library (perhaps in
+   some namespace) with the header that should be included to locate them.  */
+
+struct header_hint
+{
+  const char *name;
+  const char *header;
+};
+
+/* A class for looking up unknown names, to attempt to locate the header
+   that should have been #include-d to declare it.  */
+
+class known_headers
+{
+ public:
+  known_headers (const header_hint *hints, size_t num_hints)
+  : m_hints (hints), m_num_hints (num_hints) {}
+
+  const char *get_header_for_name (const char *name) const;
+
+ private:
+  const header_hint *const m_hints;
+  const size_t m_num_hints;
+};
+
+/* Subclass of deferred_diagnostic for suggesting to the user
+   that they have missed a #include.  */
+
+class suggest_missing_header : public deferred_diagnostic
+{
+ public:
+  suggest_missing_header (location_t loc, const char *name,
+			  const char *header_hint);
+  ~suggest_missing_header ();
+
+ private:
+  const char *m_name_str;
+  const char *m_header_hint;
+};
+
+#endif /* GCC_KNOWN_HEADERS_H */
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index ce4cb3e..fe55365 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -54,6 +54,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "spellcheck-tree.h"
 #include "gcc-rich-location.h"
 #include "asan.h"
+#include "c-family/known-headers.h"
 
 /* In grokdeclarator, distinguish syntactic contexts of declarators.  */
 enum decl_context
@@ -3991,15 +3992,31 @@  lookup_name_in_scope (tree name, struct c_scope *scope)
 static const char *
 get_c_name_hint (const char *name)
 {
-  struct std_name_hint
-  {
-    const char *name;
-    const char *header;
-  };
-  static const std_name_hint hints[] = {
+  static const header_hint hints[] = {
     /* <errno.h>.  */
     {"errno", "<errno.h>"},
 
+    /* <limits.h>.  */
+    {"CHAR_BIT", "<limits.h>"},
+    {"CHAR_MAX", "<limits.h>"},
+    {"CHAR_MIN", "<limits.h>"},
+    {"INT_MAX", "<limits.h>"},
+    {"INT_MIN", "<limits.h>"},
+    {"LLONG_MAX", "<limits.h>"},
+    {"LLONG_MIN", "<limits.h>"},
+    {"LONG_MAX", "<limits.h>"},
+    {"LONG_MIN", "<limits.h>"},
+    {"MB_LEN_MAX", "<limits.h>"},
+    {"SCHAR_MAX", "<limits.h>"},
+    {"SCHAR_MIN", "<limits.h>"},
+    {"SHRT_MAX", "<limits.h>"},
+    {"SHRT_MIN", "<limits.h>"},
+    {"UCHAR_MAX", "<limits.h>"},
+    {"UINT_MAX", "<limits.h>"},
+    {"ULLONG_MAX", "<limits.h>"},
+    {"ULONG_MAX", "<limits.h>"},
+    {"USHRT_MAX", "<limits.h>"},
+
     /* <stdarg.h>.  */
     {"va_list", "<stdarg.h>"},
 
@@ -4017,49 +4034,26 @@  get_c_name_hint (const char *name)
     {"fpos_t", "<stdio.h>"},
     {"stderr", "<stdio.h>"},
     {"stdin", "<stdio.h>"},
-    {"stdout", "<stdio.h>"}
+    {"stdout", "<stdio.h>"},
+
+    /* <stdint.h>.  */
+    {"PTRDIFF_MAX", "<stdint.h>"},
+    {"PTRDIFF_MIN", "<stdint.h>"},
+    {"SIG_ATOMIC_MAX", "<stdint.h>"},
+    {"SIG_ATOMIC_MIN", "<stdint.h>"},
+    {"SIZE_MAX", "<stdint.h>"},
+
+    /* <wchar.h>.  */
+    {"WCHAR_MAX", "<wchar.h>"},
+    {"WCHAR_MIN", "<wchar.h>"},
+    {"WINT_MAX", "<wchar.h>"},
+    {"WINT_MIN", "<wchar.h>"}
   };
   const size_t num_hints = sizeof (hints) / sizeof (hints[0]);
-  for (size_t i = 0; i < num_hints; i++)
-    {
-      if (0 == strcmp (name, hints[i].name))
-	return hints[i].header;
-    }
-  return NULL;
+  known_headers kh (hints, num_hints);
+  return kh.get_header_for_name (name);
 }
 
-/* Subclass of deferred_diagnostic for suggesting to the user
-   that they have missed a #include.  */
-
-class suggest_missing_header : public deferred_diagnostic
-{
- public:
-  suggest_missing_header (location_t loc, const char *name,
-			  const char *header_hint)
-  : deferred_diagnostic (loc), m_name_str (name), m_header_hint (header_hint)
-  {
-    gcc_assert (name);
-    gcc_assert (header_hint);
-  }
-
-  ~suggest_missing_header ()
-  {
-    if (is_suppressed_p ())
-      return;
-
-    gcc_rich_location richloc (get_location ());
-    maybe_add_include_fixit (&richloc, m_header_hint);
-    inform_at_rich_loc (&richloc,
-			"%qs is defined in header %qs;"
-			" did you forget to %<#include %s%>?",
-			m_name_str, m_header_hint, m_header_hint);
-  }
-
- private:
-  const char *m_name_str;
-  const char *m_header_hint;
-};
-
 /* Look for the closest match for NAME within the currently valid
    scopes.
 
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index dec93ad..b86ee4f 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -32,6 +32,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "gcc-rich-location.h"
 #include "spellcheck-tree.h"
 #include "parser.h"
+#include "c-family/known-headers.h"
 
 static cxx_binding *cxx_binding_make (tree value, tree type);
 static cp_binding_level *innermost_nonclass_level (void);
@@ -5392,12 +5393,7 @@  suggest_alternatives_for (location_t location, tree name,
 static const char *
 get_std_name_hint (const char *name)
 {
-  struct std_name_hint
-  {
-    const char *name;
-    const char *header;
-  };
-  static const std_name_hint hints[] = {
+  static const header_hint hints[] = {
     /* <array>.  */
     {"array", "<array>"}, // C++11
     /* <deque>.  */
@@ -5456,12 +5452,8 @@  get_std_name_hint (const char *name)
     {"vector", "<vector>"},
   };
   const size_t num_hints = sizeof (hints) / sizeof (hints[0]);
-  for (size_t i = 0; i < num_hints; i++)
-    {
-      if (0 == strcmp (name, hints[i].name))
-	return hints[i].header;
-    }
-  return NULL;
+  known_headers kh (hints, num_hints);
+  return kh.get_header_for_name (name);
 }
 
 /* If SCOPE is the "std" namespace, then suggest pertinent header
@@ -5660,6 +5652,70 @@  class macro_use_before_def : public deferred_diagnostic
   cpp_hashnode *m_macro;
 };
 
+/* Subroutine of lookup_name_fuzzy for handling unrecognized names
+   for some of the names within the C++ standard library.
+   Given non-NULL NAME, return the header name defining it within the C++
+   standard library (with '<' and '>'), or NULL.  */
+
+static const char *
+get_stdlib_name_hint (const char *name)
+{
+  static const header_hint hints[] = {
+    /* <cerrno>.  */
+    {"errno", "<cerrno>"},
+
+    /* <climits>.  */
+    {"CHAR_BIT", "<climits>"},
+    {"CHAR_MAX", "<climits>"},
+    {"CHAR_MIN", "<climits>"},
+    {"INT_MAX", "<climits>"},
+    {"INT_MIN", "<climits>"},
+    {"LLONG_MAX", "<climits>"},
+    {"LLONG_MIN", "<climits>"},
+    {"LONG_MAX", "<climits>"},
+    {"LONG_MIN", "<climits>"},
+    {"MB_LEN_MAX", "<climits>"},
+    {"SCHAR_MAX", "<climits>"},
+    {"SCHAR_MIN", "<climits>"},
+    {"SHRT_MAX", "<climits>"},
+    {"SHRT_MIN", "<climits>"},
+    {"UCHAR_MAX", "<climits>"},
+    {"UINT_MAX", "<climits>"},
+    {"ULLONG_MAX", "<climits>"},
+    {"ULONG_MAX", "<climits>"},
+    {"USHRT_MAX", "<climits>"},
+
+    /* <cstdarg>.  */
+    {"va_list", "<cstdarg>"},
+
+    /* <cstddef>.  */
+    {"NULL", "<cstddef>"},
+    {"nullptr_t", "<cstddef>"},
+    {"offsetof", "<cstddef>"},
+    {"ptrdiff_t", "<cstddef>"},
+    {"size_t", "<cstddef>"},
+
+    /* <cstdio>.  */
+    {"BUFSIZ", "<cstdio>"},
+    {"EOF", "<cstdio>"},
+    {"FILE", "<cstdio>"},
+    {"FILENAME_MAX", "<cstdio>"},
+    {"fpos_t", "<cstdio>"},
+    {"stderr", "<cstdio>"},
+    {"stdin", "<cstdio>"},
+    {"stdout", "<cstdio>"},
+
+    /* <cstdint>.  */
+    {"PTRDIFF_MAX", "<cstdint>"},
+    {"PTRDIFF_MIN", "<cstdint>"},
+    {"SIG_ATOMIC_MAX", "<cstdint>"},
+    {"SIG_ATOMIC_MIN", "<cstdint>"},
+    {"SIZE_MAX", "<cstdint>"},
+  };
+  const size_t num_hints = sizeof (hints) / sizeof (hints[0]);
+  known_headers kh (hints, num_hints);
+  return kh.get_header_for_name (name);
+}
 
 /* Search for near-matches for NAME within the current bindings, and within
    macro names, returning the best match as a const char *, or NULL if
@@ -5672,6 +5728,15 @@  lookup_name_fuzzy (tree name, enum lookup_name_fuzzy_kind kind, location_t loc)
 {
   gcc_assert (TREE_CODE (name) == IDENTIFIER_NODE);
 
+  /* First, try some well-known names in the C++ standard library, in case
+     the user forgot a #include.  */
+  const char *header_hint = get_stdlib_name_hint (IDENTIFIER_POINTER (name));
+  if (header_hint)
+    return name_hint (NULL,
+		      new suggest_missing_header (loc,
+						  IDENTIFIER_POINTER (name),
+						  header_hint));
+
   best_match <tree, const char *> bm (name);
 
   cp_binding_level *lvl;
diff --git a/gcc/testsuite/g++.dg/spellcheck-stdlib.C b/gcc/testsuite/g++.dg/spellcheck-stdlib.C
new file mode 100644
index 0000000..6e6ab1d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/spellcheck-stdlib.C
@@ -0,0 +1,84 @@ 
+/* Missing <cstddef>.  */
+
+void *ptr = NULL; // { dg-error "'NULL' was not declared" }
+// { dg-message "'NULL' is defined in header '<cstddef>'; did you forget to '#include <cstddef>'?" "" { target *-*-* } .-1 }
+
+ptrdiff_t pd; // { dg-error "'ptrdiff_t' does not name a type" }
+// { dg-message "'ptrdiff_t' is defined in header '<cstddef>'; did you forget to '#include <cstddef>'?" "" { target *-*-* } .-1 }
+
+size_t sz; // { dg-error "'size_t' does not name a type" }
+// { dg-message "'size_t' is defined in header '<cstddef>'; did you forget to '#include <cstddef>'?" "" { target *-*-* } .-1 }
+
+/* Missing <cstdio>.  */
+
+void test_cstdio (void)
+{
+  FILE *f; // { dg-error "'FILE' was not declared in this scope" }
+  // { dg-message "'FILE' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?" "" { target *-*-* } .-1 }
+  // { dg-error "'f' was not declared in this scope" "" { target *-*-* } .-2 }
+  // { dg-bogus "suggested alternative: 'if'" "PR c++/80567" { xfail *-*-* } .-3 }
+
+  char buf[BUFSIZ]; // { dg-error "'BUFSIZ' was not declared" }
+  // { dg-message "'BUFSIZ' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?" "" { target *-*-* } .-1 }
+
+  char buf2[FILENAME_MAX]; // { dg-error "'FILENAME_MAX' was not declared" }
+  // { dg-message "'FILENAME_MAX' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?" "" { target *-*-* } .-1 }
+
+  stderr; // { dg-error "'stderr' was not declared" }
+  // { dg-message "'stderr' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?" "" { target *-*-* } .-1 }
+
+  stdin; // { dg-error "'stdin' was not declared" }
+  // { dg-message "'stdin' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?" "" { target *-*-* } .-1 }
+
+  stdout; // { dg-error "'stdout' was not declared" }
+  // { dg-message "'stdout' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?" "" { target *-*-* } .-1 }
+
+  EOF; // { dg-error "'EOF' was not declared" }
+  // { dg-message "'EOF' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?" "" { target *-*-* } .-1 }
+}
+
+/* Missing <cerrno>.  */
+
+int test_cerrno (void)
+{
+  return errno; // { dg-error "'errno' was not declared" }
+  // { dg-message "'errno' is defined in header '<cerrno>'; did you forget to '#include <cerrno>'?" "" { target *-*-* } .-1 }
+}
+
+/* Missing <cstdarg>.  */
+
+void test_cstdarg (void)
+{
+  va_list ap; // { dg-error "'va_list'" }
+  // { dg-message "'va_list' is defined in header '<cstdarg>'; did you forget to '#include <cstdarg>'?" "" { target *-*-* } .-1 }
+}
+
+/* Missing <climits>.  */
+int test_INT_MAX (void)
+{
+  return INT_MAX; // { dg-line INT_MAX_line }
+  // { dg-error "'INT_MAX' was not declared" "" { target *-*-* } INT_MAX_line }
+  // { dg-bogus "__INT_MAX__" "" { target *-*-* } INT_MAX_line }
+  // { dg-message "'INT_MAX' is defined in header '<climits>'; did you forget to '#include <climits>'?" "" { target *-*-* } INT_MAX_line }
+}
+
+/* Verify that we don't offer suggestions to stdlib globals names when
+   there's an explicit namespace.  */
+
+namespace some_ns {}
+
+int not_within_namespace (void)
+{
+  return some_ns::stdout; // { dg-error "'stdout' is not a member of 'some_ns'" }
+  // { dg-bogus "is defined in header" "" { target *-*-* } .-1 }
+}
+
+/* Similarly for when there's an explicit class scope.  */
+
+class some_class {};
+
+int not_within_class (void)
+{
+  return some_class::stdout; // { dg-error "'stdout' is not a member of 'some_class'" }
+  // { dg-bogus "is defined in header" "" { target *-*-* } .-1 }
+}
diff --git a/gcc/testsuite/gcc.dg/spellcheck-stdlib.c b/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
index 85a21c3..7474c9a 100644
--- a/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
+++ b/gcc/testsuite/gcc.dg/spellcheck-stdlib.c
@@ -53,3 +53,12 @@  void test_stdarg_h (void)
   va_list ap; /* { dg-error "unknown type name 'va_list'" } */
   /* { dg-message "'va_list' is defined in header '<stdarg.h>'; did you forget to '#include <stdarg.h>'?" "" { target *-*-* } .-1 } */
 }
+
+/* Missing <limits.h>.  */
+int test_INT_MAX (void)
+{
+  return INT_MAX; /* { dg-line INT_MAX_line } */
+  /* { dg-error "'INT_MAX' undeclared" "" { target *-*-* } INT_MAX_line } */
+  /* { dg-bogus "__INT_MAX__" "" { target *-*-* } INT_MAX_line } */
+  /* { dg-message "'INT_MAX' is defined in header '<limits.h>'; did you forget to '#include <limits.h>'?" "" { target *-*-* } INT_MAX_line } */
+}