path: root/gcc/substring-locations.c

/* Source locations within string literals.
   Copyright (C) 2016-2020 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 "intl.h"
#include "diagnostic.h"
#include "cpplib.h"
#include "tree.h"
#include "langhooks.h"
#include "substring-locations.h"
#include "gcc-rich-location.h"

/* format_string_diagnostic_t's ctor, giving information for use by
   the emit_warning* member functions, as follows:

   They attempt to obtain precise location information within a string
   literal from FMT_LOC.

   Case 1: if substring location is available, and is within the range of
   the format string itself, the primary location of the
   diagnostic is the substring range obtained from FMT_LOC, with the
   caret at the *end* of the substring range.

   For example:

     test.c:90:10: warning: problem with '%i' here [-Wformat=]
     printf ("hello %i", msg);
                    ~^

   Case 2: if the substring location is available, but is not within
   the range of the format string, the primary location is that of the
   format string, and a note is emitted showing the substring location.

   For example:
     test.c:90:10: warning: problem with '%i' here [-Wformat=]
     printf("hello " INT_FMT " world", msg);
            ^~~~~~~~~~~~~~~~~~~~~~~~~
     test.c:19: note: format string is defined here
     #define INT_FMT "%i"
                      ~^

   Case 3: if precise substring information is unavailable, the primary
   location is that of the whole string passed to FMT_LOC's constructor.
   For example:

     test.c:90:10: warning: problem with '%i' here [-Wformat=]
     printf(fmt, msg);
            ^~~

   For each of cases 1-3, if param_loc is not UNKNOWN_LOCATION, then it is used
   as a secondary range within the warning.  For example, here it
   is used with case 1:

     test.c:90:16: warning: '%s' here but arg 2 has 'long' type [-Wformat=]
     printf ("foo %s bar", long_i + long_j);
                  ~^       ~~~~~~~~~~~~~~~

   and here with case 2:

     test.c:90:16: warning: '%s' here but arg 2 has 'long' type [-Wformat=]
     printf ("foo " STR_FMT " bar", long_i + long_j);
             ^~~~~~~~~~~~~~~~~~~~~  ~~~~~~~~~~~~~~~
     test.c:89:16: note: format string is defined here
     #define STR_FMT "%s"
                      ~^

   and with case 3:

     test.c:90:10: warning: '%i' here, but arg 2 is "const char *' [-Wformat=]
     printf(fmt, msg);
            ^~~  ~~~

   If non-NULL, then FMT_LABEL will be used to label the location within the
   string for cases 1 and 2; if non-NULL, then PARAM_LABEL will be used to label
   the parameter.  For example with case 1:

    test.c:90:16: warning: '%s' here but arg 2 has 'long' type [-Wformat=]
     printf ("foo %s bar", long_i + long_j);
                  ~^       ~~~~~~~~~~~~~~~
                                  |
                                  int

   and with case 2:

     test.c:90:10: warning: problem with '%i' here [-Wformat=]
     printf("hello " INT_FMT " world", msg);
            ^~~~~~~~~~~~~~~~~~~~~~~~~
     test.c:19: note: format string is defined here
     #define INT_FMT "%i"
                      ~^
                       |
                       int

   If CORRECTED_SUBSTRING is non-NULL, use it for cases 1 and 2 to provide
   a fix-it hint, suggesting that it should replace the text within the
   substring range.  For example:

     test.c:90:10: warning: problem with '%i' here [-Wformat=]
     printf ("hello %i", msg);
                    ~^
                    %s

*/

format_string_diagnostic_t::
format_string_diagnostic_t (const substring_loc &fmt_loc,
			    const range_label *fmt_label,
			    location_t param_loc,
			    const range_label *param_label,
			    const char *corrected_substring)
: m_fmt_loc (fmt_loc),
  m_fmt_label (fmt_label),
  m_param_loc (param_loc),
  m_param_label (param_label),
  m_corrected_substring (corrected_substring)
{
}

/* Emit a warning governed by option OPT, using SINGULAR_GMSGID as the
   format string (or if PLURAL_GMSGID is different from SINGULAR_GMSGID,
   using SINGULAR_GMSGID, PLURAL_GMSGID and N as arguments to ngettext)
   and AP as its arguments.

   Return true if a warning was emitted, false otherwise.  */

bool
format_string_diagnostic_t::emit_warning_n_va (int opt,
					       unsigned HOST_WIDE_INT n,
					       const char *singular_gmsgid,
					       const char *plural_gmsgid,
					       va_list *ap) const
{
  bool substring_within_range = false;
  location_t primary_loc;
  location_t fmt_substring_loc = UNKNOWN_LOCATION;
  source_range fmt_loc_range
    = get_range_from_loc (line_table, m_fmt_loc.get_fmt_string_loc ());
  const char *err = m_fmt_loc.get_location (&fmt_substring_loc);
  source_range fmt_substring_range
    = get_range_from_loc (line_table, fmt_substring_loc);
  if (err)
    /* Case 3: unable to get substring location.  */
    primary_loc = m_fmt_loc.get_fmt_string_loc ();
  else
    {
      if (fmt_substring_range.m_start >= fmt_loc_range.m_start
	  && fmt_substring_range.m_start <= fmt_loc_range.m_finish
	  && fmt_substring_range.m_finish >= fmt_loc_range.m_start
	  && fmt_substring_range.m_finish <= fmt_loc_range.m_finish)
	/* Case 1.  */
	{
	  substring_within_range = true;
	  primary_loc = fmt_substring_loc;
	}
      else
	/* Case 2.  */
	{
	  substring_within_range = false;
	  primary_loc = m_fmt_loc.get_fmt_string_loc ();
	}
    }

  /* Only use fmt_label in the initial warning for case 1.  */
  const range_label *primary_label = NULL;
  if (substring_within_range)
    primary_label = m_fmt_label;

  auto_diagnostic_group d;
  gcc_rich_location richloc (primary_loc, primary_label);

  if (m_param_loc != UNKNOWN_LOCATION)
    richloc.add_range (m_param_loc, SHOW_RANGE_WITHOUT_CARET, m_param_label);

  if (!err && m_corrected_substring && substring_within_range)
    richloc.add_fixit_replace (fmt_substring_range, m_corrected_substring);

  diagnostic_info diagnostic;
  if (singular_gmsgid != plural_gmsgid)
    {
      unsigned long gtn;

      if (sizeof n <= sizeof gtn)
	gtn = n;
      else
	/* Use the largest number ngettext can handle, otherwise
	   preserve the six least significant decimal digits for
	   languages where the plural form depends on them.  */
	gtn = n <= ULONG_MAX ? n : n % 1000000LU + 1000000LU;

      const char *text = ngettext (singular_gmsgid, plural_gmsgid, gtn);
      diagnostic_set_info_translated (&diagnostic, text, ap, &richloc,
				      DK_WARNING);
    }
  else
    diagnostic_set_info (&diagnostic, singular_gmsgid, ap, &richloc,
			 DK_WARNING);
  diagnostic.option_index = opt;
  bool warned = diagnostic_report_diagnostic (global_dc, &diagnostic);

  if (!err && fmt_substring_loc && !substring_within_range)
    /* Case 2.  */
    if (warned)
      {
	/* Use fmt_label in the note for case 2.  */
	rich_location substring_richloc (line_table, fmt_substring_loc,
					 m_fmt_label);
	if (m_corrected_substring)
	  substring_richloc.add_fixit_replace (fmt_substring_range,
					       m_corrected_substring);
	inform (&substring_richloc,
		"format string is defined here");
      }

  return warned;
}

/* Singular-only version of the above.  */

bool
format_string_diagnostic_t::emit_warning_va (int opt, const char *gmsgid,
					     va_list *ap) const
{
  return emit_warning_n_va (opt, 0, gmsgid, gmsgid, ap);
}

/* Variadic version of the above (singular only).  */

bool
format_string_diagnostic_t::emit_warning (int opt, const char *gmsgid,
					  ...) const
{
  va_list ap;
  va_start (ap, gmsgid);
  bool warned = emit_warning_va (opt, gmsgid, &ap);
  va_end (ap);

  return warned;
}

/* Variadic version of the above (singular vs plural).  */

bool
format_string_diagnostic_t::emit_warning_n (int opt, unsigned HOST_WIDE_INT n,
					    const char *singular_gmsgid,
					    const char *plural_gmsgid,
					    ...) const
{
  va_list ap;
  va_start (ap, plural_gmsgid);
  bool warned = emit_warning_n_va (opt, n, singular_gmsgid, plural_gmsgid,
				   &ap);
  va_end (ap);

  return warned;
}

/* Attempt to determine the source location of the substring.
   If successful, return NULL and write the source location to *OUT_LOC.
   Otherwise return an error message.  Error messages are intended
   for GCC developers (to help debugging) rather than for end-users.  */

const char *
substring_loc::get_location (location_t *out_loc) const
{
  gcc_assert (out_loc);
  return lang_hooks.get_substring_location (*this, out_loc);
}