Date: Thu, 8 Aug 1996 19:04:04 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
To: Frank Frederiksen <ff AT kom DOT auc DOT dk>
Cc: djgpp AT delorie DOT com
Subject: Re: Q: Compiling Emacs 19.32
In-Reply-To: <4ucac5$f6l@newsfeed.cs.auc.dk>
Message-Id: <Pine.SUN.3.91.960808185641.20906C-100000@is>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


On 8 Aug 1996, Frank Frederiksen wrote:

> I have just downloaded emacs 19.32 via ftp. After I unpacked it, I
> read in the install that:
> 
> >The current version of djgpp 2.0 (as of August 1996) has two bugs that
> >affect Emacs.  We've included corrected versions of two files from
> >djgpp in the msdos subdirectory: is-exec.c and sigaction.c.  To work
> >around the bugs, compile these files and link them into temacs.  The
> >next version of djgpp should have these bugs fixed.
> 
> However, I have two problems:
> 1) The two .c files are not in the msdos directory as stated

That's a bug in the shell script used to make the distribution.  Emacs 
19.33 (should be available in a few days) will have this corrected.  I 
attach the fixed files below, so you don't have to wait.

> 2) how do I specifically compile them and link them into temacs.

Put the two files attached to this message anywhere you like and then 
type the following words of wisdom from the DOS prompt:

	gcc -Wall -O2 -c is_exec.c
	gcc -Wall -O2 -c sigaction.c
	ar rvs c:/djgpp/lib/libc.a is_exec.o sigaction.o

(replace c:/djgpp with the correct path of DJGPP on your system).
That's it!  Now your libc.a library has the patched versions of these 
functions instead of the original ones.  After that build Emacs as usual, 
and it will be linked with the patched functions.

> Or should I rather wait for a new release of djgpp?

That is always an option.

---------------------- is_exec.c -----------------------------------
/* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
/* IS_EXEC.C
 *
 * Given a filename or a file handle, and the extension of the file,
 * determine if the file is executable.
 * First, the file extension is checked in case it uniquely identifies
 * the file as either an executable or not.  Failing this, the first
 * two bytes of the file are tested for known signatures of executable
 * files.
 *
 * Copyright (c) 1994 Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
 *
 * This software may be used freely so long as this copyright notice is
 * left intact.  There is no warranty on this software.
 *
 */

#include <libc/stubs.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <dpmi.h>
#include <go32.h>
#include <io.h>
#include <libc/farptrgs.h>
#include <libc/dosio.h>

extern unsigned short _djstat_flags;
unsigned short        _get_magic(const char *, int);
int                   _is_executable(const char *, int, const char *);

/*
 * Read a MAGIC NUMBER from a given file.  These are the first
 * two bytes of the file, if we look at them as an unsigned short. */

#define _STAT_EXEC_EXT      2   /* get execute bits from file extension? */
#define _STAT_EXEC_MAGIC    4   /* get execute bits from magic signature? */

unsigned short
_get_magic(const char *s, int fh)
{
  __dpmi_regs          regs;
  unsigned short       retval;
  unsigned short       fpos_high = 0, fpos_low = 0;
  int                  read_fail = 0;

  /* If given a pathname, open the file. */
  if (s)
  {
    int handle;
    if((handle = _open(s,0)) == -1)
      return 0;
    regs.x.bx = handle;
  }
  /* Else file already open.  Remember its current file position
     and move to beginning of file. */
  else
  {
    regs.x.ax = 0x4201;		/* set pointer from current position */
    regs.x.bx = fh;
    regs.x.cx = regs.x.dx = 0;	/* move 0 bytes (i.e., stay put) */
    __dpmi_int(0x21, &regs);
    if (regs.x.flags & 1)
    {
      errno = __doserr_to_errno(regs.x.ax);
      return 0;
    }
    fpos_high = regs.x.dx;	/* got current position */
    fpos_low  = regs.x.ax;

    regs.x.ax = 0x4200;		/* set pointer from the beginning of file */
    regs.x.cx = regs.x.dx = 0;	/* move to beginning of file */
    __dpmi_int(0x21, &regs);
    if (regs.x.flags & 1)
    {
      errno = __doserr_to_errno(regs.x.ax);
      return 0;
    }
  }
  regs.x.ds = __tb_segment;
  regs.x.dx = __tb_offset;

  /* Read 2 bytes from the file. */
  regs.x.ax = 0x3f00;
  regs.x.cx = 2;
  __dpmi_int(0x21, &regs);

  /* We can either (1) succeed, (2) read less than 2 bytes,
     or (3) fail to read at all.  */
  if (regs.x.ax != 2)
    read_fail = (regs.x.flags & 1) ? regs.x.ax : -1;

  /* If called with filename, close the file. */
  if (s)
  {
    regs.x.ax = 0x3e00;
    __dpmi_int(0x21, &regs);
    if (regs.x.flags & 1)
      errno = __doserr_to_errno(regs.x.ax);
  }
  /* Else leave file pointer where we found it. */
  else
  {
    regs.x.ax = 0x4200;		/* set pointer from the beginning of file */
    regs.x.bx = fh;
    regs.x.cx = fpos_high;
    regs.x.dx = fpos_low;
    __dpmi_int(0x21, &regs);
    if (regs.x.flags & 1)
    {
      errno = __doserr_to_errno(regs.x.ax);
      return 0;
    }
  }

  if (read_fail == 0)
    retval = _farpeekw(_dos_ds, __tb);
  else
  {
    /* The file couldn't be read: assume non-executable.  If the file
       *is* executable, but was passed as a file-handle, and the user
       opened it in write-only mode, they lose...  */
    retval = 0;
    if (read_fail != -1)
      errno = __doserr_to_errno(read_fail);
  }

  return retval;
}

/* A list of extensions which designate executable files.  These
   are NOT tested for the magic number.  */
static char executables[] = "|EXE|COM|BAT|BTM|DLL|VXD|";

/* A list of extensions which belong to files known to NEVER be
   executables.  These exist to minimize read()'ing files while
   detecting executables by magic number.  You are welcome to
   add to this list, but remember: only extensions which could
   NEVER be present in executables should go here.  */
static char non_executables[] = "\
|A|A01|A02|A03|A04|A05|ADL|ARC|ARJ|ASC|ASM|AUX|AWK\
|BAS|BIB|BGI|BMP\
|C|CC|CFG|CGZ|CH3|CHR|CI|CLP|CMF|CPI|CPP|CXX\
|DAT|DBF|DIZ|DOC|DVI\
|E|EL|ELC\
|F77|FN3\
|GIF|GZ\
|H|HLP|HPP|HXX\
|ICO|IN|INC|INF|INI\
|JPG\
|L|LEX|LF|LIB|LOG|LST|LZH\
|M|MAK|MAP|MF|MID|MPG\
|O|OBJ\
|PAK|PAS|PBM|PCD|PCX|PDS|PIC|PIF|PN3|PRJ|PS\
|RAS|RGB|RLE\
|S|SND|SY3\
|TAR|TAZ|TEX|TGA|TGZ|TIF|TXH|TXI|TXT\
|VOC\
|WAV|WK1|WK3|WKB|WQ1|WQ3|WQ4|WQ5|WQ6|WQ!\
|XBM\
|Y\
|ZIP|ZOO|";

int
_is_executable(const char *filename, int fhandle, const char *extension)
{
  if (!extension && filename)
  {
    const char *cp, *ep=0;
    for (cp=filename; *cp; cp++)
    {
      if (*cp == '.')
	ep = cp;
      if (*cp == '/' || *cp == '\\' || *cp == ':')
	ep = 0;
    }
    extension = ep;
  }
  if ((_djstat_flags & _STAT_EXEC_EXT) == 0
      && extension
      && *extension
      && strlen(extension) <= ((extension[0]=='.') ? 4 : 3))
    {
      /* Search the list of extensions in executables[]. */
      char tmp_buf[6], *tp = tmp_buf;

      *tp++ = '|';
      if (*extension == '.')
	extension++;
      while (*extension)
	*tp++ = toupper (*extension++);
      *tp++ = '|';
      *tp = '\0';
      if (strstr(non_executables, tmp_buf))
        return 0;
      else if (strstr(executables, tmp_buf))
        return 1;
    }

  /* No extension, or extension doesn't define execute
     bits unambiguously.  We are in for some dirty work.
     Read the first two bytes of the file and see if they
     are any of the known magic numbers which designate
     executable files.
     Unix-like shells, which have executable shell scripts
     without extensions and DON'T have "#!" as their FIRST
     TWO CHARACTERS, lose here.  Sorry, folks.  */
  if ( (_djstat_flags & _STAT_EXEC_MAGIC) == 0 )
    {
      switch (_get_magic(filename, fhandle))
        {
          case 0x5a4d:      /* "MZ" */
          case 0x010b:
          case 0x014c:
          case 0x2123:      /* "#!" */
              return 1;
        }
    }

  return 0;
}

-------------------- sigaction.c --------------------------
/* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
#include <signal.h>
#include <errno.h>

int
sigaction(int _sig, const struct sigaction *_act, struct sigaction *_oact)
{
  int retval = 0;

  if (_oact)
  {
    void (*installed_sig)(int) = signal (_sig, SIG_IGN);

    /* FIXME */
    if (installed_sig == SIG_ERR)
    {
      retval = -1;
      errno = EINVAL;
    }
    else
      signal (_sig, installed_sig);
    _oact->sa_handler = installed_sig;
    retval = sigemptyset (&_oact->sa_mask);
    _oact->sa_flags = 0;
  }
  if (_act)
  {
    if (signal (_sig, _act->sa_handler) == SIG_ERR)
    {
      retval = -1;
      errno = EINVAL;
    }
  }
  return 0;
}