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[official-gcc.git] / gcc / pretty-print.c

/* Various declarations for language-independent pretty-print subroutines.
   Copyright (C) 2003-2013 Free Software Foundation, Inc.
   Contributed by Gabriel Dos Reis <gdr@integrable-solutions.net>

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 "pretty-print.h"

#if HAVE_ICONV
#include <iconv.h>
#endif

/* A pointer to the formatted diagnostic message.  */
#define pp_formatted_text_data(PP) \
   ((const char *) obstack_base (pp_base (PP)->buffer->obstack))

/* Format an integer given by va_arg (ARG, type-specifier T) where
   type-specifier is a precision modifier as indicated by PREC.  F is
   a string used to construct the appropriate format-specifier.  */
#define pp_integer_with_precision(PP, ARG, PREC, T, F)       \
  do                                                         \
    switch (PREC)                                            \
      {                                                      \
      case 0:                                                \
        pp_scalar (PP, "%" F, va_arg (ARG, T));              \
        break;                                               \
                                                             \
      case 1:                                                \
        pp_scalar (PP, "%l" F, va_arg (ARG, long T));        \
        break;                                               \
                                                             \
      case 2:                                                \
        pp_scalar (PP, "%" HOST_LONG_LONG_FORMAT F, va_arg (ARG, long long T));  \
        break;                                               \
                                                             \
      default:                                               \
        break;                                               \
      }                                                      \
  while (0)


/* Subroutine of pp_set_maximum_length.  Set up PRETTY-PRINTER's
   internal maximum characters per line.  */
static void
pp_set_real_maximum_length (pretty_printer *pp)
{
  /* If we're told not to wrap lines then do the obvious thing.  In case
     we'll emit prefix only once per message, it is appropriate
     not to increase unnecessarily the line-length cut-off.  */
  if (!pp_is_wrapping_line (pp)
      || pp_prefixing_rule (pp) == DIAGNOSTICS_SHOW_PREFIX_ONCE
      || pp_prefixing_rule (pp) == DIAGNOSTICS_SHOW_PREFIX_NEVER)
    pp->maximum_length = pp_line_cutoff (pp);
  else
    {
      int prefix_length = pp->prefix ? strlen (pp->prefix) : 0;
      /* If the prefix is ridiculously too long, output at least
         32 characters.  */
      if (pp_line_cutoff (pp) - prefix_length < 32)
        pp->maximum_length = pp_line_cutoff (pp) + 32;
      else
        pp->maximum_length = pp_line_cutoff (pp);
    }
}

/* Clear PRETTY-PRINTER's output state.  */
static inline void
pp_clear_state (pretty_printer *pp)
{
  pp->emitted_prefix = false;
  pp_indentation (pp) = 0;
}

/* Flush the formatted text of PRETTY-PRINTER onto the attached stream.  */
void
pp_write_text_to_stream (pretty_printer *pp)
{
  const char *text = pp_formatted_text (pp);
  fputs (text, pp->buffer->stream);
  pp_clear_output_area (pp);
}

/* As pp_write_text_to_stream, but for GraphViz label output.

   Flush the formatted text of pretty-printer PP onto the attached stream.
   Replace characters in PPF that have special meaning in a GraphViz .dot
   file.
   
   This routine is not very fast, but it doesn't have to be as this is only
   be used by routines dumping intermediate representations in graph form.  */

void
pp_write_text_as_dot_label_to_stream (pretty_printer *pp, bool for_record)
{
  const char *text = pp_formatted_text (pp);
  const char *p = text;
  FILE *fp = pp->buffer->stream;

  while (*p)
    {
      switch (*p)
        {
        /* Print newlines as a left-aligned newline.  */
        case '\n':
          fputs ("\\l\\\n", fp);
          break;

        /* A pipe is only special for record-shape nodes.  */
        case '|':
          if (for_record)
            fputc ('\\', fp);
          fputc (*p, fp);
          break;

        /* The following characters always have to be escaped
           for use in labels.  */
        case '{':
        case '}':
        case '<':
        case '>':
        case '"':
        case ' ':
          fputc ('\\', fp);
          /* fall through */
        default:
          fputc (*p, fp);
          break;
        }
      p++;
    }

  pp_clear_output_area (pp);
}

/* Wrap a text delimited by START and END into PRETTY-PRINTER.  */
static void
pp_wrap_text (pretty_printer *pp, const char *start, const char *end)
{
  bool wrapping_line = pp_is_wrapping_line (pp);

  while (start != end)
    {
      /* Dump anything bordered by whitespaces.  */
      {
        const char *p = start;
        while (p != end && !ISBLANK (*p) && *p != '\n')
          ++p;
        if (wrapping_line
            && p - start >= pp_remaining_character_count_for_line (pp))
          pp_newline (pp);
        pp_append_text (pp, start, p);
        start = p;
      }

      if (start != end && ISBLANK (*start))
        {
          pp_space (pp);
          ++start;
        }
      if (start != end && *start == '\n')
        {
          pp_newline (pp);
          ++start;
        }
    }
}

/* Same as pp_wrap_text but wrap text only when in line-wrapping mode.  */
static inline void
pp_maybe_wrap_text (pretty_printer *pp, const char *start, const char *end)
{
  if (pp_is_wrapping_line (pp))
    pp_wrap_text (pp, start, end);
  else
    pp_append_text (pp, start, end);
}

/* Append to the output area of PRETTY-PRINTER a string specified by its
   STARTing character and LENGTH.  */
static inline void
pp_append_r (pretty_printer *pp, const char *start, int length)
{
  obstack_grow (pp->buffer->obstack, start, length);
  pp->buffer->line_length += length;
}

/* Insert enough spaces into the output area of PRETTY-PRINTER to bring
   the column position to the current indentation level, assuming that a
   newline has just been written to the buffer.  */
void
pp_base_indent (pretty_printer *pp)
{
  int n = pp_indentation (pp);
  int i;

  for (i = 0; i < n; ++i)
    pp_space (pp);
}

/* The following format specifiers are recognized as being client independent:
   %d, %i: (signed) integer in base ten.
   %u: unsigned integer in base ten.
   %o: unsigned integer in base eight.
   %x: unsigned integer in base sixteen.
   %ld, %li, %lo, %lu, %lx: long versions of the above.
   %lld, %lli, %llo, %llu, %llx: long long versions.
   %wd, %wi, %wo, %wu, %wx: HOST_WIDE_INT versions.
   %c: character.
   %s: string.
   %p: pointer.
   %m: strerror(text->err_no) - does not consume a value from args_ptr.
   %%: '%'.
   %<: opening quote.
   %>: closing quote.
   %': apostrophe (should only be used in untranslated messages;
       translations should use appropriate punctuation directly).
   %.*s: a substring the length of which is specified by an argument
         integer.
   %Ns: likewise, but length specified as constant in the format string.
   Flag 'q': quote formatted text (must come immediately after '%').

   Arguments can be used sequentially, or through %N$ resp. *N$
   notation Nth argument after the format string.  If %N$ / *N$
   notation is used, it must be used for all arguments, except %m, %%,
   %<, %> and %', which may not have a number, as they do not consume
   an argument.  When %M$.*N$s is used, M must be N + 1.  (This may
   also be written %M$.*s, provided N is not otherwise used.)  The
   format string must have conversion specifiers with argument numbers
   1 up to highest argument; each argument may only be used once.
   A format string can have at most 30 arguments.  */

/* Formatting phases 1 and 2: render TEXT->format_spec plus
   TEXT->args_ptr into a series of chunks in PP->buffer->args[].
   Phase 3 is in pp_base_format_text.  */

void
pp_base_format (pretty_printer *pp, text_info *text)
{
  output_buffer *buffer = pp->buffer;
  const char *p;
  const char **args;
  struct chunk_info *new_chunk_array;

  unsigned int curarg = 0, chunk = 0, argno;
  pp_wrapping_mode_t old_wrapping_mode;
  bool any_unnumbered = false, any_numbered = false;
  const char **formatters[PP_NL_ARGMAX];

  /* Allocate a new chunk structure.  */
  new_chunk_array = XOBNEW (&buffer->chunk_obstack, struct chunk_info);
  new_chunk_array->prev = buffer->cur_chunk_array;
  buffer->cur_chunk_array = new_chunk_array;
  args = new_chunk_array->args;

  /* Formatting phase 1: split up TEXT->format_spec into chunks in
     PP->buffer->args[].  Even-numbered chunks are to be output
     verbatim, odd-numbered chunks are format specifiers.
     %m, %%, %<, %>, and %' are replaced with the appropriate text at
     this point.  */

  memset (formatters, 0, sizeof formatters);

  for (p = text->format_spec; *p; )
    {
      while (*p != '\0' && *p != '%')
        {
          obstack_1grow (&buffer->chunk_obstack, *p);
          p++;
        }

      if (*p == '\0')
        break;

      switch (*++p)
        {
        case '\0':
          gcc_unreachable ();

        case '%':
          obstack_1grow (&buffer->chunk_obstack, '%');
          p++;
          continue;

        case '<':
          obstack_grow (&buffer->chunk_obstack,
                        open_quote, strlen (open_quote));
          p++;
          continue;

        case '>':
        case '\'':
          obstack_grow (&buffer->chunk_obstack,
                        close_quote, strlen (close_quote));
          p++;
          continue;

        case 'm':
          {
            const char *errstr = xstrerror (text->err_no);
            obstack_grow (&buffer->chunk_obstack, errstr, strlen (errstr));
          }
          p++;
          continue;

        default:
          /* Handled in phase 2.  Terminate the plain chunk here.  */
          obstack_1grow (&buffer->chunk_obstack, '\0');
          gcc_assert (chunk < PP_NL_ARGMAX * 2);
          args[chunk++] = XOBFINISH (&buffer->chunk_obstack, const char *);
          break;
        }

      if (ISDIGIT (*p))
        {
          char *end;
          argno = strtoul (p, &end, 10) - 1;
          p = end;
          gcc_assert (*p == '$');
          p++;

          any_numbered = true;
          gcc_assert (!any_unnumbered);
        }
      else
        {
          argno = curarg++;
          any_unnumbered = true;
          gcc_assert (!any_numbered);
        }
      gcc_assert (argno < PP_NL_ARGMAX);
      gcc_assert (!formatters[argno]);
      formatters[argno] = &args[chunk];
      do
        {
          obstack_1grow (&buffer->chunk_obstack, *p);
          p++;
        }
      while (strchr ("qwl+#", p[-1]));

      if (p[-1] == '.')
        {
          /* We handle '%.Ns' and '%.*s' or '%M$.*N$s'
             (where M == N + 1).  */
          if (ISDIGIT (*p))
            {
              do
                {
                  obstack_1grow (&buffer->chunk_obstack, *p);
                  p++;
                }
              while (ISDIGIT (p[-1]));
              gcc_assert (p[-1] == 's');
            }
          else
            {
              gcc_assert (*p == '*');
              obstack_1grow (&buffer->chunk_obstack, '*');
              p++;

              if (ISDIGIT (*p))
                {
                  char *end;
                  unsigned int argno2 = strtoul (p, &end, 10) - 1;
                  p = end;
                  gcc_assert (argno2 == argno - 1);
                  gcc_assert (!any_unnumbered);
                  gcc_assert (*p == '$');

                  p++;
                  formatters[argno2] = formatters[argno];
                }
              else
                {
                  gcc_assert (!any_numbered);
                  formatters[argno+1] = formatters[argno];
                  curarg++;
                }
              gcc_assert (*p == 's');
              obstack_1grow (&buffer->chunk_obstack, 's');
              p++;
            }
        }
      if (*p == '\0')
        break;

      obstack_1grow (&buffer->chunk_obstack, '\0');
      gcc_assert (chunk < PP_NL_ARGMAX * 2);
      args[chunk++] = XOBFINISH (&buffer->chunk_obstack, const char *);
    }

  obstack_1grow (&buffer->chunk_obstack, '\0');
  gcc_assert (chunk < PP_NL_ARGMAX * 2);
  args[chunk++] = XOBFINISH (&buffer->chunk_obstack, const char *);
  args[chunk] = 0;

  /* Set output to the argument obstack, and switch line-wrapping and
     prefixing off.  */
  buffer->obstack = &buffer->chunk_obstack;
  old_wrapping_mode = pp_set_verbatim_wrapping (pp);

  /* Second phase.  Replace each formatter with the formatted text it
     corresponds to.  */

  for (argno = 0; formatters[argno]; argno++)
    {
      int precision = 0;
      bool wide = false;
      bool plus = false;
      bool hash = false;
      bool quote = false;

      /* We do not attempt to enforce any ordering on the modifier
         characters.  */

      for (p = *formatters[argno];; p++)
        {
          switch (*p)
            {
            case 'q':
              gcc_assert (!quote);
              quote = true;
              continue;

            case '+':
              gcc_assert (!plus);
              plus = true;
              continue;

            case '#':
              gcc_assert (!hash);
              hash = true;
              continue;

            case 'w':
              gcc_assert (!wide);
              wide = true;
              continue;

            case 'l':
              /* We don't support precision beyond that of "long long".  */
              gcc_assert (precision < 2);
              precision++;
              continue;
            }
          break;
        }

      gcc_assert (!wide || precision == 0);

      if (quote)
        pp_string (pp, open_quote);

      switch (*p)
        {
        case 'c':
          pp_character (pp, va_arg (*text->args_ptr, int));
          break;

        case 'd':
        case 'i':
          if (wide)
            pp_wide_integer (pp, va_arg (*text->args_ptr, HOST_WIDE_INT));
          else
            pp_integer_with_precision
              (pp, *text->args_ptr, precision, int, "d");
          break;

        case 'o':
          if (wide)
            pp_scalar (pp, "%" HOST_WIDE_INT_PRINT "o",
                       va_arg (*text->args_ptr, unsigned HOST_WIDE_INT));
          else
            pp_integer_with_precision
              (pp, *text->args_ptr, precision, unsigned, "o");
          break;

        case 's':
          pp_string (pp, va_arg (*text->args_ptr, const char *));
          break;

        case 'p':
          pp_pointer (pp, va_arg (*text->args_ptr, void *));
          break;

        case 'u':
          if (wide)
            pp_scalar (pp, HOST_WIDE_INT_PRINT_UNSIGNED,
                       va_arg (*text->args_ptr, unsigned HOST_WIDE_INT));
          else
            pp_integer_with_precision
              (pp, *text->args_ptr, precision, unsigned, "u");
          break;

        case 'x':
          if (wide)
            pp_scalar (pp, HOST_WIDE_INT_PRINT_HEX,
                       va_arg (*text->args_ptr, unsigned HOST_WIDE_INT));
          else
            pp_integer_with_precision
              (pp, *text->args_ptr, precision, unsigned, "x");
          break;

        case '.':
          {
            int n;
            const char *s;

            /* We handle '%.Ns' and '%.*s' or '%M$.*N$s'
               (where M == N + 1).  The format string should be verified
               already from the first phase.  */
            p++;
            if (ISDIGIT (*p))
              {
                char *end;
                n = strtoul (p, &end, 10);
                p = end;
                gcc_assert (*p == 's');
              }
            else
              {
                gcc_assert (*p == '*');
                p++;
                gcc_assert (*p == 's');
                n = va_arg (*text->args_ptr, int);

                /* This consumes a second entry in the formatters array.  */
                gcc_assert (formatters[argno] == formatters[argno+1]);
                argno++;
              }

            s = va_arg (*text->args_ptr, const char *);
            pp_append_text (pp, s, s + n);
          }
          break;

        default:
          {
            bool ok;

            gcc_assert (pp_format_decoder (pp));
            ok = pp_format_decoder (pp) (pp, text, p,
                                         precision, wide, plus, hash);
            gcc_assert (ok);
          }
        }

      if (quote)
        pp_string (pp, close_quote);

      obstack_1grow (&buffer->chunk_obstack, '\0');
      *formatters[argno] = XOBFINISH (&buffer->chunk_obstack, const char *);
    }

#ifdef ENABLE_CHECKING
  for (; argno < PP_NL_ARGMAX; argno++)
    gcc_assert (!formatters[argno]);
#endif

  /* Revert to normal obstack and wrapping mode.  */
  buffer->obstack = &buffer->formatted_obstack;
  buffer->line_length = 0;
  pp_wrapping_mode (pp) = old_wrapping_mode;
  pp_clear_state (pp);
}

/* Format of a message pointed to by TEXT.  */
void
pp_base_output_formatted_text (pretty_printer *pp)
{
  unsigned int chunk;
  output_buffer *buffer = pp_buffer (pp);
  struct chunk_info *chunk_array = buffer->cur_chunk_array;
  const char **args = chunk_array->args;

  gcc_assert (buffer->obstack == &buffer->formatted_obstack);
  gcc_assert (buffer->line_length == 0);

  /* This is a third phase, first 2 phases done in pp_base_format_args.
     Now we actually print it.  */
  for (chunk = 0; args[chunk]; chunk++)
    pp_string (pp, args[chunk]);

  /* Deallocate the chunk structure and everything after it (i.e. the
     associated series of formatted strings).  */
  buffer->cur_chunk_array = chunk_array->prev;
  obstack_free (&buffer->chunk_obstack, chunk_array);
}

/* Helper subroutine of output_verbatim and verbatim. Do the appropriate
   settings needed by BUFFER for a verbatim formatting.  */
void
pp_base_format_verbatim (pretty_printer *pp, text_info *text)
{
  /* Set verbatim mode.  */
  pp_wrapping_mode_t oldmode = pp_set_verbatim_wrapping (pp);

  /* Do the actual formatting.  */
  pp_format (pp, text);
  pp_output_formatted_text (pp);

  /* Restore previous settings.  */
  pp_wrapping_mode (pp) = oldmode;
}

/* Flush the content of BUFFER onto the attached stream.  */
void
pp_base_flush (pretty_printer *pp)
{
  pp_write_text_to_stream (pp);
  pp_clear_state (pp);
  fflush (pp->buffer->stream);
}

/* Sets the number of maximum characters per line PRETTY-PRINTER can
   output in line-wrapping mode.  A LENGTH value 0 suppresses
   line-wrapping.  */
void
pp_base_set_line_maximum_length (pretty_printer *pp, int length)
{
  pp_line_cutoff (pp) = length;
  pp_set_real_maximum_length (pp);
}

/* Clear PRETTY-PRINTER output area text info.  */
void
pp_base_clear_output_area (pretty_printer *pp)
{
  obstack_free (pp->buffer->obstack, obstack_base (pp->buffer->obstack));
  pp->buffer->line_length = 0;
}

/* Set PREFIX for PRETTY-PRINTER.  */
void
pp_base_set_prefix (pretty_printer *pp, const char *prefix)
{
  pp->prefix = prefix;
  pp_set_real_maximum_length (pp);
  pp->emitted_prefix = false;
  pp_indentation (pp) = 0;
}

/* Free PRETTY-PRINTER's prefix, a previously malloc()'d string.  */
void
pp_base_destroy_prefix (pretty_printer *pp)
{
  if (pp->prefix != NULL)
    {
      free (CONST_CAST (char *, pp->prefix));
      pp->prefix = NULL;
    }
}

/* Write out PRETTY-PRINTER's prefix.  */
void
pp_base_emit_prefix (pretty_printer *pp)
{
  if (pp->prefix != NULL)
    {
      switch (pp_prefixing_rule (pp))
        {
        default:
        case DIAGNOSTICS_SHOW_PREFIX_NEVER:
          break;

        case DIAGNOSTICS_SHOW_PREFIX_ONCE:
          if (pp->emitted_prefix)
            {
              pp_base_indent (pp);
              break;
            }
          pp_indentation (pp) += 3;
          /* Fall through.  */

        case DIAGNOSTICS_SHOW_PREFIX_EVERY_LINE:
          {
            int prefix_length = strlen (pp->prefix);
            pp_append_r (pp, pp->prefix, prefix_length);
            pp->emitted_prefix = true;
          }
          break;
        }
    }
}

/* Construct a PRETTY-PRINTER with PREFIX and of MAXIMUM_LENGTH
   characters per line.  */
void
pp_construct (pretty_printer *pp, const char *prefix, int maximum_length)
{
  memset (pp, 0, sizeof (pretty_printer));
  pp->buffer = XCNEW (output_buffer);
  obstack_init (&pp->buffer->chunk_obstack);
  obstack_init (&pp->buffer->formatted_obstack);
  pp->buffer->obstack = &pp->buffer->formatted_obstack;
  pp->buffer->stream = stderr;
  pp_line_cutoff (pp) = maximum_length;
  pp_prefixing_rule (pp) = DIAGNOSTICS_SHOW_PREFIX_ONCE;
  pp_set_prefix (pp, prefix);
  pp_translate_identifiers (pp) = true;
}

/* Append a string delimited by START and END to the output area of
   PRETTY-PRINTER.  No line wrapping is done.  However, if beginning a
   new line then emit PRETTY-PRINTER's prefix and skip any leading
   whitespace if appropriate.  The caller must ensure that it is
   safe to do so.  */
void
pp_base_append_text (pretty_printer *pp, const char *start, const char *end)
{
  /* Emit prefix and skip whitespace if we're starting a new line.  */
  if (pp->buffer->line_length == 0)
    {
      pp_emit_prefix (pp);
      if (pp_is_wrapping_line (pp))
        while (start != end && *start == ' ')
          ++start;
    }
  pp_append_r (pp, start, end - start);
}

/* Finishes constructing a NULL-terminated character string representing
   the PRETTY-PRINTED text.  */
const char *
pp_base_formatted_text (pretty_printer *pp)
{
  obstack_1grow (pp->buffer->obstack, '\0');
  return pp_formatted_text_data (pp);
}

/*  Return a pointer to the last character emitted in PRETTY-PRINTER's
    output area.  A NULL pointer means no character available.  */
const char *
pp_base_last_position_in_text (const pretty_printer *pp)
{
  const char *p = NULL;
  struct obstack *text = pp->buffer->obstack;

  if (obstack_base (text) != obstack_next_free (text))
    p = ((const char *) obstack_next_free (text)) - 1;
  return p;
}

/* Return the amount of characters PRETTY-PRINTER can accept to
   make a full line.  Meaningful only in line-wrapping mode.  */
int
pp_base_remaining_character_count_for_line (pretty_printer *pp)
{
  return pp->maximum_length - pp->buffer->line_length;
}


/* Format a message into BUFFER a la printf.  */
void
pp_printf (pretty_printer *pp, const char *msg, ...)
{
  text_info text;
  va_list ap;

  va_start (ap, msg);
  text.err_no = errno;
  text.args_ptr = &ap;
  text.format_spec = msg;
  text.locus = NULL;
  pp_format (pp, &text);
  pp_output_formatted_text (pp);
  va_end (ap);
}


/* Output MESSAGE verbatim into BUFFER.  */
void
pp_verbatim (pretty_printer *pp, const char *msg, ...)
{
  text_info text;
  va_list ap;

  va_start (ap, msg);
  text.err_no = errno;
  text.args_ptr = &ap;
  text.format_spec = msg;
  text.locus = NULL;
  pp_format_verbatim (pp, &text);
  va_end (ap);
}



/* Have PRETTY-PRINTER start a new line.  */
void
pp_base_newline (pretty_printer *pp)
{
  obstack_1grow (pp->buffer->obstack, '\n');
  pp_needs_newline (pp) = false;
  pp->buffer->line_length = 0;
}

/* Have PRETTY-PRINTER add a CHARACTER.  */
void
pp_base_character (pretty_printer *pp, int c)
{
  if (pp_is_wrapping_line (pp)
      && pp_remaining_character_count_for_line (pp) <= 0)
    {
      pp_newline (pp);
      if (ISSPACE (c))
        return;
    }
  obstack_1grow (pp->buffer->obstack, c);
  ++pp->buffer->line_length;
}

/* Append a STRING to the output area of PRETTY-PRINTER; the STRING may
   be line-wrapped if in appropriate mode.  */
void
pp_base_string (pretty_printer *pp, const char *str)
{
  pp_maybe_wrap_text (pp, str, str + (str ? strlen (str) : 0));
}

/* Maybe print out a whitespace if needed.  */

void
pp_base_maybe_space (pretty_printer *pp)
{
  if (pp_base (pp)->padding != pp_none)
    {
      pp_space (pp);
      pp_base (pp)->padding = pp_none;
    }
}
\f
/* The string starting at P has LEN (at least 1) bytes left; if they
   start with a valid UTF-8 sequence, return the length of that
   sequence and set *VALUE to the value of that sequence, and
   otherwise return 0 and set *VALUE to (unsigned int) -1.  */

static int
decode_utf8_char (const unsigned char *p, size_t len, unsigned int *value)
{
  unsigned int t = *p;

  if (len == 0)
    abort ();
  if (t & 0x80)
    {
      size_t utf8_len = 0;
      unsigned int ch;
      size_t i;
      for (t = *p; t & 0x80; t <<= 1)
        utf8_len++;

      if (utf8_len > len || utf8_len < 2 || utf8_len > 6)
        {
          *value = (unsigned int) -1;
          return 0;
        }
      ch = *p & ((1 << (7 - utf8_len)) - 1);
      for (i = 1; i < utf8_len; i++)
        {
          unsigned int u = p[i];
          if ((u & 0xC0) != 0x80)
            {
              *value = (unsigned int) -1;
              return 0;
            }
          ch = (ch << 6) | (u & 0x3F);
        }
      if (   (ch <=      0x7F && utf8_len > 1)
          || (ch <=     0x7FF && utf8_len > 2)
          || (ch <=    0xFFFF && utf8_len > 3)
          || (ch <=  0x1FFFFF && utf8_len > 4)
          || (ch <= 0x3FFFFFF && utf8_len > 5)
          || (ch >= 0xD800 && ch <= 0xDFFF))
        {
          *value = (unsigned int) -1;
          return 0;
        }
      *value = ch;
      return utf8_len;
    }
  else
    {
      *value = t;
      return 1;
    }
}

/* Allocator for identifier_to_locale and corresponding function to
   free memory.  */

void *(*identifier_to_locale_alloc) (size_t) = xmalloc;
void (*identifier_to_locale_free) (void *) = free;

/* Given IDENT, an identifier in the internal encoding, return a
   version of IDENT suitable for diagnostics in the locale character
   set: either IDENT itself, or a string, allocated using
   identifier_to_locale_alloc, converted to the locale character set
   and using escape sequences if not representable in the locale
   character set or containing control characters or invalid byte
   sequences.  Existing backslashes in IDENT are not doubled, so the
   result may not uniquely specify the contents of an arbitrary byte
   sequence identifier.  */

const char *
identifier_to_locale (const char *ident)
{
  const unsigned char *uid = (const unsigned char *) ident;
  size_t idlen = strlen (ident);
  bool valid_printable_utf8 = true;
  bool all_ascii = true;
  size_t i;

  for (i = 0; i < idlen;)
    {
      unsigned int c;
      size_t utf8_len = decode_utf8_char (&uid[i], idlen - i, &c);
      if (utf8_len == 0 || c <= 0x1F || (c >= 0x7F && c <= 0x9F))
        {
          valid_printable_utf8 = false;
          break;
        }
      if (utf8_len > 1)
        all_ascii = false;
      i += utf8_len;
    }

  /* If IDENT contains invalid UTF-8 sequences (which may occur with
     attributes putting arbitrary byte sequences in identifiers), or
     control characters, we use octal escape sequences for all bytes
     outside printable ASCII.  */
  if (!valid_printable_utf8)
    {
      char *ret = (char *) identifier_to_locale_alloc (4 * idlen + 1);
      char *p = ret;
      for (i = 0; i < idlen; i++)
        {
          if (uid[i] > 0x1F && uid[i] < 0x7F)
            *p++ = uid[i];
          else
            {
              sprintf (p, "\\%03o", uid[i]);
              p += 4;
            }
        }
      *p = 0;
      return ret;
    }

  /* Otherwise, if it is valid printable ASCII, or printable UTF-8
     with the locale character set being UTF-8, IDENT is used.  */
  if (all_ascii || locale_utf8)
    return ident;

  /* Otherwise IDENT is converted to the locale character set if
     possible.  */
#if defined ENABLE_NLS && defined HAVE_LANGINFO_CODESET && HAVE_ICONV
  if (locale_encoding != NULL)
    {
      iconv_t cd = iconv_open (locale_encoding, "UTF-8");
      bool conversion_ok = true;
      char *ret = NULL;
      if (cd != (iconv_t) -1)
        {
          size_t ret_alloc = 4 * idlen + 1;
          for (;;)
            {
              /* Repeat the whole conversion process as needed with
                 larger buffers so non-reversible transformations can
                 always be detected.  */
              ICONV_CONST char *inbuf = CONST_CAST (char *, ident);
              char *outbuf;
              size_t inbytesleft = idlen;
              size_t outbytesleft = ret_alloc - 1;
              size_t iconv_ret;

              ret = (char *) identifier_to_locale_alloc (ret_alloc);
              outbuf = ret;

              if (iconv (cd, 0, 0, 0, 0) == (size_t) -1)
                {
                  conversion_ok = false;
                  break;
                }

              iconv_ret = iconv (cd, &inbuf, &inbytesleft,
                                 &outbuf, &outbytesleft);
              if (iconv_ret == (size_t) -1 || inbytesleft != 0)
                {
                  if (errno == E2BIG)
                    {
                      ret_alloc *= 2;
                      identifier_to_locale_free (ret);
                      ret = NULL;
                      continue;
                    }
                  else
                    {
                      conversion_ok = false;
                      break;
                    }
                }
              else if (iconv_ret != 0)
                {
                  conversion_ok = false;
                  break;
                }
              /* Return to initial shift state.  */
              if (iconv (cd, 0, 0, &outbuf, &outbytesleft) == (size_t) -1)
                {
                  if (errno == E2BIG)
                    {
                      ret_alloc *= 2;
                      identifier_to_locale_free (ret);
                      ret = NULL;
                      continue;
                    }
                  else
                    {
                      conversion_ok = false;
                      break;
                    }
                }
              *outbuf = 0;
              break;
            }
          iconv_close (cd);
          if (conversion_ok)
            return ret;
        }
    }
#endif

  /* Otherwise, convert non-ASCII characters in IDENT to UCNs.  */
  {
    char *ret = (char *) identifier_to_locale_alloc (10 * idlen + 1);
    char *p = ret;
    for (i = 0; i < idlen;)
      {
        unsigned int c;
        size_t utf8_len = decode_utf8_char (&uid[i], idlen - i, &c);
        if (utf8_len == 1)
          *p++ = uid[i];
        else
          {
            sprintf (p, "\\U%08x", c);
            p += 10;
          }
        i += utf8_len;
      }
    *p = 0;
    return ret;
  }
}