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

This patch 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).

gcc/ChangeLog:
	PR c/81404
	* Makefile.in (C_COMMON_OBJS): Add c-family/known-headers.o.

gcc/c-family/ChangeLog:
	PR c/81404
	* known-headers.cc: New file, based on material from c/c-decl.c.
	(suggest_missing_header): Copied as-is.
	(get_stdlib_header_for_name): New, based on get_c_name_hint but
	heavily edited to add C++ support.  Add some knowledge about
	<limits.h>, <stdint.h>, and <wchar.h>.
	* known-headers.h: Likewise.

gcc/c/ChangeLog:
	PR c/81404
	* c-decl.c: Include "c-family/known-headers.h".
	(get_c_name_hint): Rename to get_stdlib_header_for_name and move
	to known-headers.cc.
	(class suggest_missing_header): Move to known-header.h.
	(lookup_name_fuzzy): Call get_c_stdlib_header_for_name rather
	than get_c_name_hint.

gcc/cp/ChangeLog:
	PR c/81404
	* name-lookup.c: Include "c-family/known-headers.h"
	(lookup_name_fuzzy): Call get_cp_stdlib_header_for_name and
	potentially return a new suggest_missing_header hint.

gcc/testsuite/ChangeLog:
	PR c/81404
	* g++.dg/spellcheck-stdlib.C: New.
	* gcc.dg/spellcheck-stdlib.c (test_INT_MAX): New.

From-SVN: r254980

3 files changed, 220 insertions, 0 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 9d49eb9..1e5c3d3 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,5 +1,15 @@
 2017-11-20  David Malcolm  <dmalcolm@redhat.com>
 
+	PR c/81404
+	* known-headers.cc: New file, based on material from c/c-decl.c.
+	(suggest_missing_header): Copied as-is.
+	(get_stdlib_header_for_name): New, based on get_c_name_hint but
+	heavily edited to add C++ support.  Add some knowledge about
+	<limits.h>, <stdint.h>, and <wchar.h>.
+	* known-headers.h: Likewise.
+
+2017-11-20  David Malcolm  <dmalcolm@redhat.com>
+
 	* c-common.h (enum lookup_name_fuzzy_kind): Move to name-hint.h.
 	(lookup_name_fuzzy): Likewise.  Convert return type from
 	const char * to name_hint.  Add location_t param.
diff --git a/gcc/c-family/known-headers.cc b/gcc/c-family/known-headers.cc
new file mode 100644
index 0000000..d4cd39b
--- /dev/null
+++ b/gcc/c-family/known-headers.cc
@@ -0,0 +1,169 @@
+/* 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"
+#define INCLUDE_UNIQUE_PTR
+#include "system.h"
+#include "coretypes.h"
+#include "c-family/c-common.h"
+#include "c-family/name-hint.h"
+#include "c-family/known-headers.h"
+#include "gcc-rich-location.h"
+
+/* An enum for distinguishing between the C and C++ stdlibs.  */
+
+enum stdlib
+{
+  STDLIB_C,
+  STDLIB_CPLUSPLUS,
+
+  NUM_STDLIBS
+};
+
+/* A struct for associating names in a standard library with the header
+   that should be included to locate them, for each of the C and C++ stdlibs
+   (or NULL, for names that aren't in a header for a particular stdlib).  */
+
+struct stdlib_hint
+{
+  const char *name;
+  const char *header[NUM_STDLIBS];
+};
+
+/* Given non-NULL NAME, return the header name defining it within either
+   the standard library (with '<' and '>'), or NULL.
+   Only handles a subset of the most common names within the stdlibs.  */
+
+static const char *
+get_stdlib_header_for_name (const char *name, enum stdlib lib)
+{
+  gcc_assert (name);
+  gcc_assert (lib < NUM_STDLIBS);
+
+  static const stdlib_hint hints[] = {
+    /* <errno.h> and <cerrno>.  */
+    {"errno", {"<errno.h>", "<cerrno>"} },
+
+    /* <limits.h> and <climits>.  */
+    {"CHAR_BIT", {"<limits.h>", "<climits>"} },
+    {"CHAR_MAX", {"<limits.h>", "<climits>"} },
+    {"CHAR_MIN", {"<limits.h>", "<climits>"} },
+    {"INT_MAX", {"<limits.h>", "<climits>"} },
+    {"INT_MIN", {"<limits.h>", "<climits>"} },
+    {"LLONG_MAX", {"<limits.h>", "<climits>"} },
+    {"LLONG_MIN", {"<limits.h>", "<climits>"} },
+    {"LONG_MAX", {"<limits.h>", "<climits>"} },
+    {"LONG_MIN", {"<limits.h>", "<climits>"} },
+    {"MB_LEN_MAX", {"<limits.h>", "<climits>"} },
+    {"SCHAR_MAX", {"<limits.h>", "<climits>"} },
+    {"SCHAR_MIN", {"<limits.h>", "<climits>"} },
+    {"SHRT_MAX", {"<limits.h>", "<climits>"} },
+    {"SHRT_MIN", {"<limits.h>", "<climits>"} },
+    {"UCHAR_MAX", {"<limits.h>", "<climits>"} },
+    {"UINT_MAX", {"<limits.h>", "<climits>"} },
+    {"ULLONG_MAX", {"<limits.h>", "<climits>"} },
+    {"ULONG_MAX", {"<limits.h>", "<climits>"} },
+    {"USHRT_MAX", {"<limits.h>", "<climits>"} },
+
+    /* <stdarg.h> and <cstdarg>.  */
+    {"va_list", {"<stdarg.h>", "<cstdarg>"} },
+
+    /* <stddef.h> and <cstddef>.  */
+    {"NULL", {"<stddef.h>", "<cstddef>"} },
+    {"nullptr_t", {NULL, "<cstddef>"} },
+    {"offsetof", {"<stddef.h>", "<cstddef>"} },
+    {"ptrdiff_t", {"<stddef.h>", "<cstddef>"} },
+    {"size_t", {"<stddef.h>", "<cstddef>"} },
+    {"wchar_t", {"<stddef.h>", NULL /* a keyword in C++ */} },
+
+    /* <stdio.h>.  */
+    {"BUFSIZ", {"<stdio.h>", "<cstdio>"} },
+    {"EOF", {"<stdio.h>", "<cstdio>"} },
+    {"FILE", {"<stdio.h>", "<cstdio>"} },
+    {"FILENAME_MAX", {"<stdio.h>", "<cstdio>"} },
+    {"fpos_t", {"<stdio.h>", "<cstdio>"} },
+    {"stderr", {"<stdio.h>", "<cstdio>"} },
+    {"stdin", {"<stdio.h>", "<cstdio>"} },
+    {"stdout", {"<stdio.h>", "<cstdio>"} },
+
+    /* <stdint.h>.  */
+    {"PTRDIFF_MAX", {"<stdint.h>", "<cstdint>"} },
+    {"PTRDIFF_MIN", {"<stdint.h>", "<cstdint>"} },
+    {"SIG_ATOMIC_MAX", {"<stdint.h>", "<cstdint>"} },
+    {"SIG_ATOMIC_MIN", {"<stdint.h>", "<cstdint>"} },
+    {"SIZE_MAX", {"<stdint.h>", "<cstdint>"} },
+    {"WINT_MAX", {"<stdint.h>", "<cstdint>"} },
+    {"WINT_MIN", {"<stdint.h>", "<cstdint>"} },
+
+    /* <wchar.h>.  */
+    {"WCHAR_MAX", {"<wchar.h>", "<cwchar>"} },
+    {"WCHAR_MIN", {"<wchar.h>", "<cwchar>"} }
+  };
+  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[lib];
+  return NULL;
+}
+
+/* Given non-NULL NAME, return the header name defining it within the C
+   standard library (with '<' and '>'), or NULL.  */
+
+const char *
+get_c_stdlib_header_for_name (const char *name)
+{
+  return get_stdlib_header_for_name (name, STDLIB_C);
+}
+
+/* Given non-NULL NAME, return the header name defining it within the C++
+   standard library (with '<' and '>'), or NULL.  */
+
+const char *
+get_cp_stdlib_header_for_name (const char *name)
+{
+  return get_stdlib_header_for_name (name, STDLIB_CPLUSPLUS);
+}
+
+/* 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 (&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..328100f
--- /dev/null
+++ b/gcc/c-family/known-headers.h
@@ -0,0 +1,41 @@
+/* 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
+
+extern const char *get_c_stdlib_header_for_name (const char *name);
+extern const char *get_cp_stdlib_header_for_name (const char *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);
+  ~suggest_missing_header ();
+
+ private:
+  const char *m_name_str;
+  const char *m_header_hint;
+};
+
+#endif /* GCC_KNOWN_HEADERS_H */