lread.c 109 KB
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/* Lisp parsing and input streams.
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   Copyright (C) 1985, 1986, 1987, 1988, 1989, 1993, 1994, 1995, 1997, 1998,
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     1999, 2000, 2001, 2003, 2004, 2005  Free Software Foundation, Inc.
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This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.

GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */
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#include <config.h>
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#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/file.h>
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#include <errno.h>
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#include "lisp.h"
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#include "intervals.h"
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#include "buffer.h"
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#include "charset.h"
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#include <epaths.h>
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#include "commands.h"
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#include "keyboard.h"
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#include "termhooks.h"
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#include "coding.h"
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#ifdef lint
#include <sys/inode.h>
#endif /* lint */

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#ifdef MSDOS
#if __DJGPP__ < 2
#include <unistd.h>	/* to get X_OK */
#endif
#include "msdos.h"
#endif

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#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

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#ifndef X_OK
#define X_OK 01
#endif

#include <math.h>

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#ifdef HAVE_SETLOCALE
#include <locale.h>
#endif /* HAVE_SETLOCALE */

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#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
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#ifndef O_RDONLY
#define O_RDONLY 0
#endif

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#ifdef HAVE_FSEEKO
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#define file_offset off_t
#define file_tell ftello
#else
#define file_offset long
#define file_tell ftell
#endif

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#ifndef USE_CRT_DLL
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extern int errno;
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#endif
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Lisp_Object Qread_char, Qget_file_char, Qstandard_input, Qcurrent_load_list;
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Lisp_Object Qvariable_documentation, Vvalues, Vstandard_input, Vafter_load_alist;
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Lisp_Object Qascii_character, Qload, Qload_file_name;
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Lisp_Object Qbackquote, Qcomma, Qcomma_at, Qcomma_dot, Qfunction;
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Lisp_Object Qinhibit_file_name_operation;
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Lisp_Object Qeval_buffer_list, Veval_buffer_list;
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extern Lisp_Object Qevent_symbol_element_mask;
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extern Lisp_Object Qfile_exists_p;
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/* non-zero iff inside `load' */
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int load_in_progress;

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/* Directory in which the sources were found.  */
Lisp_Object Vsource_directory;

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/* Search path and suffixes for files to be loaded. */
Lisp_Object Vload_path, Vload_suffixes, default_suffixes;
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/* File name of user's init file.  */
Lisp_Object Vuser_init_file;

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/* This is the user-visible association list that maps features to
   lists of defs in their load files. */
Lisp_Object Vload_history;

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/* This is used to build the load history. */
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Lisp_Object Vcurrent_load_list;

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/* List of files that were preloaded.  */
Lisp_Object Vpreloaded_file_list;

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/* Name of file actually being read by `load'.  */
Lisp_Object Vload_file_name;

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/* Function to use for reading, in `load' and friends.  */
Lisp_Object Vload_read_function;

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/* The association list of objects read with the #n=object form.
   Each member of the list has the form (n . object), and is used to
   look up the object for the corresponding #n# construct.
   It must be set to nil before all top-level calls to read0.  */
Lisp_Object read_objects;

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/* Nonzero means load should forcibly load all dynamic doc strings.  */
static int load_force_doc_strings;

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/* Nonzero means read should convert strings to unibyte.  */
static int load_convert_to_unibyte;

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/* Function to use for loading an Emacs lisp source file (not
   compiled) instead of readevalloop.  */
Lisp_Object Vload_source_file_function;

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/* List of all DEFVAR_BOOL variables.  Used by the byte optimizer.  */
Lisp_Object Vbyte_boolean_vars;

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/* Whether or not to add a `read-positions' property to symbols
   read. */
Lisp_Object Vread_with_symbol_positions;

/* List of (SYMBOL . POSITION) accumulated so far. */
Lisp_Object Vread_symbol_positions_list;

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/* List of descriptors now open for Fload.  */
static Lisp_Object load_descriptor_list;

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/* File for get_file_char to read from.  Use by load.  */
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static FILE *instream;

/* When nonzero, read conses in pure space */
static int read_pure;

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/* For use within read-from-string (this reader is non-reentrant!!)  */
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static int read_from_string_index;
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static int read_from_string_index_byte;
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static int read_from_string_limit;
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/* Number of bytes left to read in the buffer character
   that `readchar' has already advanced over.  */
static int readchar_backlog;
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/* Number of characters read in the current call to Fread or
   Fread_from_string. */
static int readchar_count;
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/* This contains the last string skipped with #@.  */
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static char *saved_doc_string;
/* Length of buffer allocated in saved_doc_string.  */
static int saved_doc_string_size;
/* Length of actual data in saved_doc_string.  */
static int saved_doc_string_length;
/* This is the file position that string came from.  */
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static file_offset saved_doc_string_position;
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/* This contains the previous string skipped with #@.
   We copy it from saved_doc_string when a new string
   is put in saved_doc_string.  */
static char *prev_saved_doc_string;
/* Length of buffer allocated in prev_saved_doc_string.  */
static int prev_saved_doc_string_size;
/* Length of actual data in prev_saved_doc_string.  */
static int prev_saved_doc_string_length;
/* This is the file position that string came from.  */
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static file_offset prev_saved_doc_string_position;
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/* Nonzero means inside a new-style backquote
   with no surrounding parentheses.
   Fread initializes this to zero, so we need not specbind it
   or worry about what happens to it when there is an error.  */
static int new_backquote_flag;
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/* A list of file names for files being loaded in Fload.  Used to
   check for recursive loads.  */

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static Lisp_Object Vloads_in_progress;
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/* Non-zero means load dangerous compiled Lisp files.  */

int load_dangerous_libraries;

/* A regular expression used to detect files compiled with Emacs.  */

static Lisp_Object Vbytecomp_version_regexp;

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static void to_multibyte P_ ((char **, char **, int *));
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static void readevalloop P_ ((Lisp_Object, FILE*, Lisp_Object,
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			      Lisp_Object (*) (), int,
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			      Lisp_Object, Lisp_Object,
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			      Lisp_Object, Lisp_Object));
static Lisp_Object load_unwind P_ ((Lisp_Object));
static Lisp_Object load_descriptor_unwind P_ ((Lisp_Object));

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/* Handle unreading and rereading of characters.
   Write READCHAR to read a character,
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   UNREAD(c) to unread c to be read again.

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   The READCHAR and UNREAD macros are meant for reading/unreading a
   byte code; they do not handle multibyte characters.  The caller
   should manage them if necessary.
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   [ Actually that seems to be a lie; READCHAR will definitely read
     multibyte characters from buffer sources, at least.  Is the
     comment just out of date?
     -- Colin Walters <walters@gnu.org>, 22 May 2002 16:36:50 -0400 ]
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 */
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#define READCHAR readchar (readcharfun)
#define UNREAD(c) unreadchar (readcharfun, c)

static int
readchar (readcharfun)
     Lisp_Object readcharfun;
{
  Lisp_Object tem;
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  register int c;
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  readchar_count++;
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  if (BUFFERP (readcharfun))
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    {
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      register struct buffer *inbuffer = XBUFFER (readcharfun);
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      int pt_byte = BUF_PT_BYTE (inbuffer);
      int orig_pt_byte = pt_byte;
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      if (readchar_backlog > 0)
	/* We get the address of the byte just passed,
	   which is the last byte of the character.
	   The other bytes in this character are consecutive with it,
	   because the gap can't be in the middle of a character.  */
	return *(BUF_BYTE_ADDRESS (inbuffer, BUF_PT_BYTE (inbuffer) - 1)
		 - --readchar_backlog);

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      if (pt_byte >= BUF_ZV_BYTE (inbuffer))
	return -1;
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      readchar_backlog = -1;

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      if (! NILP (inbuffer->enable_multibyte_characters))
	{
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	  /* Fetch the character code from the buffer.  */
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	  unsigned char *p = BUF_BYTE_ADDRESS (inbuffer, pt_byte);
	  BUF_INC_POS (inbuffer, pt_byte);
	  c = STRING_CHAR (p, pt_byte - orig_pt_byte);
	}
      else
	{
	  c = BUF_FETCH_BYTE (inbuffer, pt_byte);
	  pt_byte++;
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	}
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      SET_BUF_PT_BOTH (inbuffer, BUF_PT (inbuffer) + 1, pt_byte);
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      return c;
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    }
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  if (MARKERP (readcharfun))
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    {
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      register struct buffer *inbuffer = XMARKER (readcharfun)->buffer;
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      int bytepos = marker_byte_position (readcharfun);
      int orig_bytepos = bytepos;
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      if (readchar_backlog > 0)
	/* We get the address of the byte just passed,
	   which is the last byte of the character.
	   The other bytes in this character are consecutive with it,
	   because the gap can't be in the middle of a character.  */
	return *(BUF_BYTE_ADDRESS (inbuffer, XMARKER (readcharfun)->bytepos - 1)
		 - --readchar_backlog);

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      if (bytepos >= BUF_ZV_BYTE (inbuffer))
	return -1;
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      readchar_backlog = -1;

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      if (! NILP (inbuffer->enable_multibyte_characters))
	{
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	  /* Fetch the character code from the buffer.  */
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	  unsigned char *p = BUF_BYTE_ADDRESS (inbuffer, bytepos);
	  BUF_INC_POS (inbuffer, bytepos);
	  c = STRING_CHAR (p, bytepos - orig_bytepos);
	}
      else
	{
	  c = BUF_FETCH_BYTE (inbuffer, bytepos);
	  bytepos++;
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	}

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      XMARKER (readcharfun)->bytepos = bytepos;
      XMARKER (readcharfun)->charpos++;

      return c;
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    }
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  if (EQ (readcharfun, Qlambda))
    return read_bytecode_char (0);

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  if (EQ (readcharfun, Qget_file_char))
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    {
      c = getc (instream);
#ifdef EINTR
      /* Interrupted reads have been observed while reading over the network */
      while (c == EOF && ferror (instream) && errno == EINTR)
	{
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	  QUIT;
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	  clearerr (instream);
	  c = getc (instream);
	}
#endif
      return c;
    }
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  if (STRINGP (readcharfun))
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    {
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      if (read_from_string_index >= read_from_string_limit)
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	c = -1;
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      else
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	FETCH_STRING_CHAR_ADVANCE (c, readcharfun,
				   read_from_string_index,
				   read_from_string_index_byte);
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      return c;
    }

  tem = call0 (readcharfun);

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  if (NILP (tem))
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    return -1;
  return XINT (tem);
}

/* Unread the character C in the way appropriate for the stream READCHARFUN.
   If the stream is a user function, call it with the char as argument.  */

static void
unreadchar (readcharfun, c)
     Lisp_Object readcharfun;
     int c;
{
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  readchar_count--;
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  if (c == -1)
    /* Don't back up the pointer if we're unreading the end-of-input mark,
       since readchar didn't advance it when we read it.  */
    ;
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  else if (BUFFERP (readcharfun))
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    {
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      struct buffer *b = XBUFFER (readcharfun);
      int bytepos = BUF_PT_BYTE (b);
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      if (readchar_backlog >= 0)
	readchar_backlog++;
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      else
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	{
	  BUF_PT (b)--;
	  if (! NILP (b->enable_multibyte_characters))
	    BUF_DEC_POS (b, bytepos);
	  else
	    bytepos--;
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	  BUF_PT_BYTE (b) = bytepos;
	}
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    }
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  else if (MARKERP (readcharfun))
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    {
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      struct buffer *b = XMARKER (readcharfun)->buffer;
      int bytepos = XMARKER (readcharfun)->bytepos;
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      if (readchar_backlog >= 0)
	readchar_backlog++;
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      else
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	{
	  XMARKER (readcharfun)->charpos--;
	  if (! NILP (b->enable_multibyte_characters))
	    BUF_DEC_POS (b, bytepos);
	  else
	    bytepos--;
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	  XMARKER (readcharfun)->bytepos = bytepos;
	}
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    }
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  else if (STRINGP (readcharfun))
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    {
      read_from_string_index--;
      read_from_string_index_byte
	= string_char_to_byte (readcharfun, read_from_string_index);
    }
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  else if (EQ (readcharfun, Qlambda))
    read_bytecode_char (1);
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  else if (EQ (readcharfun, Qget_file_char))
    ungetc (c, instream);
  else
    call1 (readcharfun, make_number (c));
}

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static Lisp_Object read_internal_start P_ ((Lisp_Object, Lisp_Object,
					    Lisp_Object));
static Lisp_Object read0 P_ ((Lisp_Object));
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static Lisp_Object read1 P_ ((Lisp_Object, int *, int));
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static Lisp_Object read_list P_ ((int, Lisp_Object));
static Lisp_Object read_vector P_ ((Lisp_Object, int));
static int read_multibyte P_ ((int, Lisp_Object));

static Lisp_Object substitute_object_recurse P_ ((Lisp_Object, Lisp_Object,
						  Lisp_Object));
static void substitute_object_in_subtree P_ ((Lisp_Object,
					      Lisp_Object));
static void substitute_in_interval P_ ((INTERVAL, Lisp_Object));
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432

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/* Get a character from the tty.  */
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extern Lisp_Object read_char ();

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/* Read input events until we get one that's acceptable for our purposes.

   If NO_SWITCH_FRAME is non-zero, switch-frame events are stashed
   until we get a character we like, and then stuffed into
   unread_switch_frame.

   If ASCII_REQUIRED is non-zero, we check function key events to see
   if the unmodified version of the symbol has a Qascii_character
   property, and use that character, if present.

   If ERROR_NONASCII is non-zero, we signal an error if the input we
   get isn't an ASCII character with modifiers.  If it's zero but
   ASCII_REQUIRED is non-zero, we just re-read until we get an ASCII
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   character.

   If INPUT_METHOD is nonzero, we invoke the current input method
   if the character warrants that.  */
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Lisp_Object
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read_filtered_event (no_switch_frame, ascii_required, error_nonascii,
		     input_method)
     int no_switch_frame, ascii_required, error_nonascii, input_method;
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{
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  register Lisp_Object val, delayed_switch_frame;

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#ifdef HAVE_WINDOW_SYSTEM
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  if (display_hourglass_p)
    cancel_hourglass ();
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#endif
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  delayed_switch_frame = Qnil;
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  /* Read until we get an acceptable event.  */
 retry:
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  val = read_char (0, 0, 0,
		   (input_method ? Qnil : Qt),
		   0);
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  if (BUFFERP (val))
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    goto retry;

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  /* switch-frame events are put off until after the next ASCII
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     character.  This is better than signaling an error just because
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     the last characters were typed to a separate minibuffer frame,
     for example.  Eventually, some code which can deal with
     switch-frame events will read it and process it.  */
  if (no_switch_frame
      && EVENT_HAS_PARAMETERS (val)
      && EQ (EVENT_HEAD (val), Qswitch_frame))
    {
      delayed_switch_frame = val;
      goto retry;
    }

  if (ascii_required)
    {
      /* Convert certain symbols to their ASCII equivalents.  */
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      if (SYMBOLP (val))
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	{
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	  Lisp_Object tem, tem1;
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	  tem = Fget (val, Qevent_symbol_element_mask);
	  if (!NILP (tem))
	    {
	      tem1 = Fget (Fcar (tem), Qascii_character);
	      /* Merge this symbol's modifier bits
		 with the ASCII equivalent of its basic code.  */
	      if (!NILP (tem1))
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		XSETFASTINT (val, XINT (tem1) | XINT (Fcar (Fcdr (tem))));
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	    }
	}
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      /* If we don't have a character now, deal with it appropriately.  */
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      if (!INTEGERP (val))
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	{
	  if (error_nonascii)
	    {
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	      Vunread_command_events = Fcons (val, Qnil);
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	      error ("Non-character input-event");
	    }
	  else
	    goto retry;
	}
    }

  if (! NILP (delayed_switch_frame))
    unread_switch_frame = delayed_switch_frame;

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#if 0

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#ifdef HAVE_WINDOW_SYSTEM
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  if (display_hourglass_p)
    start_hourglass ();
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#endif
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#endif

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  return val;
}

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DEFUN ("read-char", Fread_char, Sread_char, 0, 2, 0,
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       doc: /* Read a character from the command input (keyboard or macro).
It is returned as a number.
If the user generates an event which is not a character (i.e. a mouse
click or function key event), `read-char' signals an error.  As an
exception, switch-frame events are put off until non-ASCII events can
be read.
If you want to read non-character events, or ignore them, call
`read-event' or `read-char-exclusive' instead.

If the optional argument PROMPT is non-nil, display that as a prompt.
If the optional argument INHERIT-INPUT-METHOD is non-nil and some
input method is turned on in the current buffer, that input method
is used for reading a character.  */)
     (prompt, inherit_input_method)
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     Lisp_Object prompt, inherit_input_method;
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{
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  if (! NILP (prompt))
    message_with_string ("%s", prompt, 0);
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  return read_filtered_event (1, 1, 1, ! NILP (inherit_input_method));
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}

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DEFUN ("read-event", Fread_event, Sread_event, 0, 2, 0,
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       doc: /* Read an event object from the input stream.
If the optional argument PROMPT is non-nil, display that as a prompt.
If the optional argument INHERIT-INPUT-METHOD is non-nil and some
input method is turned on in the current buffer, that input method
is used for reading a character.  */)
     (prompt, inherit_input_method)
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     Lisp_Object prompt, inherit_input_method;
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{
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  if (! NILP (prompt))
    message_with_string ("%s", prompt, 0);
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  return read_filtered_event (0, 0, 0, ! NILP (inherit_input_method));
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}

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DEFUN ("read-char-exclusive", Fread_char_exclusive, Sread_char_exclusive, 0, 2, 0,
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       doc: /* Read a character from the command input (keyboard or macro).
It is returned as a number.  Non-character events are ignored.

If the optional argument PROMPT is non-nil, display that as a prompt.
If the optional argument INHERIT-INPUT-METHOD is non-nil and some
input method is turned on in the current buffer, that input method
is used for reading a character.  */)
     (prompt, inherit_input_method)
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     Lisp_Object prompt, inherit_input_method;
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{
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  if (! NILP (prompt))
    message_with_string ("%s", prompt, 0);
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  return read_filtered_event (1, 1, 0, ! NILP (inherit_input_method));
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}

DEFUN ("get-file-char", Fget_file_char, Sget_file_char, 0, 0, 0,
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       doc: /* Don't use this yourself.  */)
     ()
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{
  register Lisp_Object val;
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  XSETINT (val, getc (instream));
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  return val;
}
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598

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/* Value is non-zero if the file asswociated with file descriptor FD
   is a compiled Lisp file that's safe to load.  Only files compiled
   with Emacs are safe to load.  Files compiled with XEmacs can lead
   to a crash in Fbyte_code because of an incompatible change in the
   byte compiler.  */

static int
safe_to_load_p (fd)
     int fd;
{
  char buf[512];
  int nbytes, i;
  int safe_p = 1;

  /* Read the first few bytes from the file, and look for a line
     specifying the byte compiler version used.  */
  nbytes = emacs_read (fd, buf, sizeof buf - 1);
  if (nbytes > 0)
    {
      buf[nbytes] = '\0';

      /* Skip to the next newline, skipping over the initial `ELC'
	 with NUL bytes following it.  */
      for (i = 0; i < nbytes && buf[i] != '\n'; ++i)
	;

      if (i < nbytes
	  && fast_c_string_match_ignore_case (Vbytecomp_version_regexp,
					      buf + i) < 0)
	safe_p = 0;
    }

  lseek (fd, 0, SEEK_SET);
  return safe_p;
}


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/* Callback for record_unwind_protect.  Restore the old load list OLD,
   after loading a file successfully.  */

static Lisp_Object
record_load_unwind (old)
     Lisp_Object old;
{
  return Vloads_in_progress = old;
}

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/* This handler function is used via internal_condition_case_1.  */

static Lisp_Object
load_error_handler (data)
     Lisp_Object data;
{
  return Qnil;
}
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DEFUN ("load", Fload, Sload, 1, 5, 0,
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       doc: /* Execute a file of Lisp code named FILE.
First try FILE with `.elc' appended, then try with `.el',
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 then try FILE unmodified (the exact suffixes are determined by
`load-suffixes').  Environment variable references in FILE
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 are replaced with their values by calling `substitute-in-file-name'.
This function searches the directories in `load-path'.
If optional second arg NOERROR is non-nil,
 report no error if FILE doesn't exist.
Print messages at start and end of loading unless
 optional third arg NOMESSAGE is non-nil.
If optional fourth arg NOSUFFIX is non-nil, don't try adding
 suffixes `.elc' or `.el' to the specified name FILE.
If optional fifth arg MUST-SUFFIX is non-nil, insist on
 the suffix `.elc' or `.el'; don't accept just FILE unless
 it ends in one of those suffixes or includes a directory name.
Return t if file exists.  */)
     (file, noerror, nomessage, nosuffix, must_suffix)
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     Lisp_Object file, noerror, nomessage, nosuffix, must_suffix;
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{
  register FILE *stream;
  register int fd = -1;
  register Lisp_Object lispstream;
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  int count = SPECPDL_INDEX ();
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  Lisp_Object temp;
  struct gcpro gcpro1;
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  Lisp_Object found, efound;
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  /* 1 means we printed the ".el is newer" message.  */
  int newer = 0;
  /* 1 means we are loading a compiled file.  */
  int compiled = 0;
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  Lisp_Object handler;
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  int safe_p = 1;
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  char *fmode = "r";
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#ifdef DOS_NT
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  fmode = "rt";
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#endif /* DOS_NT */
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  CHECK_STRING (file);
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  /* If file name is magic, call the handler.  */
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  /* This shouldn't be necessary any more now that `openp' handles it right.
    handler = Ffind_file_name_handler (file, Qload);
    if (!NILP (handler))
      return call5 (handler, Qload, file, noerror, nomessage, nosuffix); */
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  /* Do this after the handler to avoid
     the need to gcpro noerror, nomessage and nosuffix.
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     (Below here, we care only whether they are nil or not.)
     The presence of this call is the result of a historical accident:
     it used to be in every file-operations and when it got removed
     everywhere, it accidentally stayed here.  Since then, enough people
     supposedly have things like (load "$PROJECT/foo.el") in their .emacs
     that it seemed risky to remove.  */
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  if (! NILP (noerror))
    {
      file = internal_condition_case_1 (Fsubstitute_in_file_name, file,
					Qt, load_error_handler);
      if (NILP (file))
	return Qnil;
    }
  else
    file = Fsubstitute_in_file_name (file);
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  /* Avoid weird lossage with null string as arg,
     since it would try to load a directory as a Lisp file */
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  if (SCHARS (file) > 0)
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    {
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      int size = SBYTES (file);
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      Lisp_Object tmp[2];
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      GCPRO1 (file);
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      if (! NILP (must_suffix))
	{
	  /* Don't insist on adding a suffix if FILE already ends with one.  */
	  if (size > 3
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	      && !strcmp (SDATA (file) + size - 3, ".el"))
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	    must_suffix = Qnil;
	  else if (size > 4
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		   && !strcmp (SDATA (file) + size - 4, ".elc"))
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	    must_suffix = Qnil;
	  /* Don't insist on adding a suffix
	     if the argument includes a directory name.  */
	  else if (! NILP (Ffile_name_directory (file)))
	    must_suffix = Qnil;
	}

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      fd = openp (Vload_path, file,
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		  (!NILP (nosuffix) ? Qnil
		   : !NILP (must_suffix) ? Vload_suffixes
		   : Fappend (2, (tmp[0] = Vload_suffixes,
				  tmp[1] = default_suffixes,
				  tmp))),
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		  &found, Qnil);
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      UNGCPRO;
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    }

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  if (fd == -1)
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    {
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      if (NILP (noerror))
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	Fsignal (Qfile_error, Fcons (build_string ("Cannot open load file"),
				     Fcons (file, Qnil)));
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      else
	return Qnil;
    }

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  /* Tell startup.el whether or not we found the user's init file.  */
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  if (EQ (Qt, Vuser_init_file))
    Vuser_init_file = found;

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  /* If FD is -2, that means openp found a magic file.  */
  if (fd == -2)
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    {
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      if (NILP (Fequal (found, file)))
	/* If FOUND is a different file name from FILE,
	   find its handler even if we have already inhibited
	   the `load' operation on FILE.  */
	handler = Ffind_file_name_handler (found, Qt);
      else
	handler = Ffind_file_name_handler (found, Qload);
      if (! NILP (handler))
	return call5 (handler, Qload, found, noerror, nomessage, Qt);
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    }

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  /* Check if we're stuck in a recursive load cycle.

     2000-09-21: It's not possible to just check for the file loaded
     being a member of Vloads_in_progress.  This fails because of the
     way the byte compiler currently works; `provide's are not
     evaluted, see font-lock.el/jit-lock.el as an example.  This
     leads to a certain amount of ``normal'' recursion.

     Also, just loading a file recursively is not always an error in
     the general case; the second load may do something different.  */
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  {
    int count = 0;
    Lisp_Object tem;
    for (tem = Vloads_in_progress; CONSP (tem); tem = XCDR (tem))
      if (!NILP (Fequal (found, XCAR (tem))))
	count++;
    if (count > 3)
      Fsignal (Qerror, Fcons (build_string ("Recursive load"),
			      Fcons (found, Vloads_in_progress)));
    record_unwind_protect (record_load_unwind, Vloads_in_progress);
    Vloads_in_progress = Fcons (found, Vloads_in_progress);
  }
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  if (!bcmp (SDATA (found) + SBYTES (found) - 4,
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	     ".elc", 4))
    /* Load .elc files directly, but not when they are
       remote and have no handler!  */
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    {
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      if (fd != -2)
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	{
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	  struct stat s1, s2;
	  int result;
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	  if (!safe_to_load_p (fd))
	    {
	      safe_p = 0;
	      if (!load_dangerous_libraries)
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		{
		  if (fd >= 0)
		    emacs_close (fd);
		  error ("File `%s' was not compiled in Emacs",
			 SDATA (found));
		}
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	      else if (!NILP (nomessage))
		message_with_string ("File `%s' not compiled in Emacs", found, 1);
	    }
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	  compiled = 1;

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	  GCPRO1 (efound);
	  efound = ENCODE_FILE (found);

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#ifdef DOS_NT
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	  fmode = "rb";
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#endif /* DOS_NT */
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	  stat ((char *)SDATA (efound), &s1);
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	  SSET (efound, SBYTES (efound) - 1, 0);
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	  result = stat ((char *)SDATA (efound), &s2);
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	  SSET (efound, SBYTES (efound) - 1, 'c');
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	  UNGCPRO;

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	  if (result >= 0 && (unsigned) s1.st_mtime < (unsigned) s2.st_mtime)
	    {
	      /* Make the progress messages mention that source is newer.  */
	      newer = 1;
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	      /* If we won't print another message, mention this anyway.  */
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	      if (!NILP (nomessage))
		{
		  Lisp_Object file;
		  file = Fsubstring (found, make_number (0), make_number (-1));
		  message_with_string ("Source file `%s' newer than byte-compiled file",
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				       file, 1);
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		}
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	    }
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	}
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    }
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  else
    {
      /* We are loading a source file (*.el).  */
      if (!NILP (Vload_source_file_function))
	{
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	  Lisp_Object val;
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	  if (fd >= 0)
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	    emacs_close (fd);
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	  val = call4 (Vload_source_file_function, found, file,
		       NILP (noerror) ? Qnil : Qt,
		       NILP (nomessage) ? Qnil : Qt);
	  return unbind_to (count, val);
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	}
    }
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#ifdef WINDOWSNT
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  emacs_close (fd);
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  GCPRO1 (efound);
  efound = ENCODE_FILE (found);
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  stream = fopen ((char *) SDATA (efound), fmode);
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  UNGCPRO;
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#else  /* not WINDOWSNT */
  stream = fdopen (fd, fmode);
#endif /* not WINDOWSNT */
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  if (stream == 0)
    {
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      emacs_close (fd);
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      error ("Failure to create stdio stream for %s", SDATA (file));
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    }

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  if (! NILP (Vpurify_flag))
    Vpreloaded_file_list = Fcons (file, Vpreloaded_file_list);

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  if (NILP (nomessage))
    {
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      if (!safe_p)
	message_with_string ("Loading %s (compiled; note unsafe, not compiled in Emacs)...",
		 file, 1);
      else if (!compiled)
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	message_with_string ("Loading %s (source)...", file, 1);
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      else if (newer)
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	message_with_string ("Loading %s (compiled; note, source file is newer)...",
		 file, 1);
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      else /* The typical case; compiled file newer than source file.  */
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	message_with_string ("Loading %s...", file, 1);
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    }
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  GCPRO1 (file);
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  lispstream = Fcons (Qnil, Qnil);
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  XSETCARFASTINT (lispstream, (EMACS_UINT)stream >> 16);
  XSETCDRFASTINT (lispstream, (EMACS_UINT)stream & 0xffff);
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  record_unwind_protect (load_unwind, lispstream);
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  record_unwind_protect (load_descriptor_unwind, load_descriptor_list);
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  specbind (Qload_file_name, found);
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  specbind (Qinhibit_file_name_operation, Qnil);
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  load_descriptor_list
    = Fcons (make_number (fileno (stream)), load_descriptor_list);
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  load_in_progress++;
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  readevalloop (Qget_file_char, stream, file, Feval,
		0, Qnil, Qnil, Qnil, Qnil);
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  unbind_to (count, Qnil);

  /* Run any load-hooks for this file.  */
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  temp = Fassoc (file, Vafter_load_alist);
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  if (!NILP (temp))
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    Fprogn (Fcdr (temp));
  UNGCPRO;

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  if (saved_doc_string)
    free (saved_doc_string);
  saved_doc_string = 0;
  saved_doc_string_size = 0;

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  if (prev_saved_doc_string)
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    xfree (prev_saved_doc_string);
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  prev_saved_doc_string = 0;
  prev_saved_doc_string_size = 0;

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  if (!noninteractive && NILP (nomessage))
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    {
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      if (!safe_p)
	message_with_string ("Loading %s (compiled; note unsafe, not compiled in Emacs)...done",
		 file, 1);
      else if (!compiled)
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	message_with_string ("Loading %s (source)...done", file, 1);
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      else if (newer)
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	message_with_string ("Loading %s (compiled; note, source file is newer)...done",
		 file, 1);
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      else /* The typical case; compiled file newer than source file.  */
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	message_with_string ("Loading %s...done", file, 1);
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    }
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  if (!NILP (Fequal (build_string ("obsolete"),
		     Ffile_name_nondirectory
		     (Fdirectory_file_name (Ffile_name_directory (found))))))
    message_with_string ("Package %s is obsolete", file, 1);

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  return Qt;
}

static Lisp_Object
load_unwind (stream)  /* used as unwind-protect function in load */
     Lisp_Object stream;
{
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  fclose ((FILE *) (XFASTINT (XCAR (stream)) << 16
		    | XFASTINT (XCDR (stream))));
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  if (--load_in_progress < 0) load_in_progress = 0;
  return Qnil;
}

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static Lisp_Object
load_descriptor_unwind (oldlist)
     Lisp_Object oldlist;
{
  load_descriptor_list = oldlist;
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  return Qnil;
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}

/* Close all descriptors in use for Floads.
   This is used when starting a subprocess.  */

void
close_load_descs ()
{
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#ifndef WINDOWSNT
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  Lisp_Object tail;
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  for (tail = load_descriptor_list; !NILP (tail); tail = XCDR (tail))
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    emacs_close (XFASTINT (XCAR (tail)));
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#endif
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}
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static int
complete_filename_p (pathname)
     Lisp_Object pathname;
{
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  register const unsigned char *s = SDATA (pathname);
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  return (IS_DIRECTORY_SEP (s[0])
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	  || (SCHARS (pathname) > 2
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	      && IS_DEVICE_SEP (s[1]) && IS_DIRECTORY_SEP (s[2]))
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#ifdef ALTOS
	  || *s == '@'
#endif
#ifdef VMS
	  || index (s, ':')
#endif /* VMS */
	  );
}

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DEFUN ("locate-file-internal", Flocate_file_internal, Slocate_file_internal, 2, 4, 0,
       doc: /* Search for FILENAME through PATH.
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Returns the file's name in absolute form, or nil if not found.
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If SUFFIXES is non-nil, it should be a list of suffixes to append to
file name when searching.
If non-nil, PREDICATE is used instead of `file-readable-p'.
PREDICATE can also be an integer to pass to the access(2) function,
in which case file-name-handlers are ignored.  */)
     (filename, path, suffixes, predicate)
     Lisp_Object filename, path, suffixes, predicate;
{
  Lisp_Object file;
  int fd = openp (path, filename, suffixes, &file, predicate);
  if (NILP (predicate) && fd > 0)
    close (fd);
  return file;
}


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/* Search for a file whose name is STR, looking in directories
   in the Lisp list PATH, and trying suffixes from SUFFIX.
   On success, returns a file descriptor.  On failure, returns -1.