gcc/c-pch.c

/* Precompiled header implementation for the C languages.
   Copyright (C) 2000, 2002, 2003 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 2, 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 COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "version.h"
#include "cpplib.h"
#include "tree.h"
#include "flags.h"
#include "c-common.h"
#include "output.h"
#include "toplev.h"
#include "debug.h"
#include "c-pragma.h"
#include "ggc.h"
#include "langhooks.h"
#include "hosthooks.h"
#include "target.h"

/* This structure is read very early when validating the PCH, and
   might be read for a PCH which is for a completely different compiler
   for a different operating system.  Thus, it should really only contain
   'unsigned char' entries, at least in the initial entries.  

   If you add or change entries before version_length, you should increase
   the version number in get_ident().  

   There are a bunch of fields named *_length; those are lengths of data that
   follows this structure in the same order as the fields in the structure.

   The flags_info field is used to verify that certain flags settings that
   have to be the same during the compilation of the PCH and a compilation
   using the PCH are indeed the same.  */

struct c_pch_validity
{
  unsigned char host_machine_length;
  unsigned char target_machine_length;
  unsigned char version_length;
  unsigned char debug_info_type;
  unsigned int flags_info;
  void (*pch_init) (void);
  size_t target_data_length;
};

/* If -funit-at-a-time is set, we require that it was also set during the
   compilation of the PCH we may be using.  */
#define FLAG_UNIT_AT_A_TIME_SET 1 << 0

struct c_pch_header 
{
  unsigned long asm_size;
};

#define IDENT_LENGTH 8

/* The file we'll be writing the PCH to.  */
static FILE *pch_outfile;

/* The position in the assembler output file when pch_init was called.  */
static long asm_file_startpos;

/* The host and target machines.  */
static const char host_machine[] = HOST_MACHINE;
static const char target_machine[] = TARGET_MACHINE;

static const char *get_ident (void);

/* Compute an appropriate 8-byte magic number for the PCH file, so that
   utilities like file(1) can identify it, and so that GCC can quickly
   ignore non-PCH files and PCH files that are of a completely different
   format.  */

static const char *
get_ident(void)
{
  static char result[IDENT_LENGTH];
  static const char template[IDENT_LENGTH] = "gpch.012";
  static const char c_language_chars[] = "Co+O";
  
  memcpy (result, template, IDENT_LENGTH);
  result[4] = c_language_chars[c_language];

  return result;
}

/* Prepare to write a PCH file.  This is called at the start of 
   compilation.  */

void
pch_init (void)
{
  FILE *f;
  struct c_pch_validity v;
  void *target_validity;
  static const char partial_pch[IDENT_LENGTH] = "gpcWrite";
  unsigned int current_flags_info = 0;
  
  if (! pch_file)
    return;

  if (flag_unit_at_a_time)
    current_flags_info |= FLAG_UNIT_AT_A_TIME_SET;

  f = fopen (pch_file, "w+b");
  if (f == NULL)
    fatal_error ("can't create precompiled header %s: %m", pch_file);
  pch_outfile = f;
  
  if (strlen (host_machine) > 255 || strlen (target_machine) > 255
      || strlen (version_string) > 255)
    abort ();
  
  v.host_machine_length = strlen (host_machine);
  v.target_machine_length = strlen (target_machine);
  v.version_length = strlen (version_string);
  v.debug_info_type = write_symbols;
  v.flags_info = current_flags_info;
  v.pch_init = &pch_init;
  target_validity = targetm.get_pch_validity (&v.target_data_length);
  
  if (fwrite (partial_pch, IDENT_LENGTH, 1, f) != 1
      || fwrite (&v, sizeof (v), 1, f) != 1
      || fwrite (host_machine, v.host_machine_length, 1, f) != 1
      || fwrite (target_machine, v.target_machine_length, 1, f) != 1
      || fwrite (version_string, v.version_length, 1, f) != 1
      || fwrite (target_validity, v.target_data_length, 1, f) != 1)
    fatal_error ("can't write to %s: %m", pch_file);

  /* We need to be able to re-read the output.  */
  /* The driver always provides a valid -o option.  */
  if (asm_file_name == NULL
      || strcmp (asm_file_name, "-") == 0)
    fatal_error ("`%s' is not a valid output file", asm_file_name);
  
  asm_file_startpos = ftell (asm_out_file);
  
  /* Let the debugging format deal with the PCHness.  */
  (*debug_hooks->handle_pch) (0);
  
  cpp_save_state (parse_in, f);
}

/* Write the PCH file.  This is called at the end of a compilation which
   will produce a PCH file.  */

void
c_common_write_pch (void)
{
  char *buf;
  long asm_file_end;
  long written;
  struct c_pch_header h;

  (*debug_hooks->handle_pch) (1);

  cpp_write_pch_deps (parse_in, pch_outfile);

  asm_file_end = ftell (asm_out_file);
  h.asm_size = asm_file_end - asm_file_startpos;
  
  if (fwrite (&h, sizeof (h), 1, pch_outfile) != 1)
    fatal_error ("can't write %s: %m", pch_file);
  
  buf = xmalloc (16384);
  fflush (asm_out_file);

  if (fseek (asm_out_file, asm_file_startpos, SEEK_SET) != 0)
    fatal_error ("can't seek in %s: %m", asm_file_name);

  for (written = asm_file_startpos; written < asm_file_end; )
    {
      long size = asm_file_end - written;
      if (size > 16384)
	size = 16384;
      if (fread (buf, size, 1, asm_out_file) != 1)
	fatal_error ("can't read %s: %m", asm_file_name);
      if (fwrite (buf, size, 1, pch_outfile) != 1)
	fatal_error ("can't write %s: %m", pch_file);
      written += size;
    }
  free (buf);
  /* asm_out_file can be written afterwards, so must be flushed first.  */
  fflush (asm_out_file);

  gt_pch_save (pch_outfile);
  cpp_write_pch_state (parse_in, pch_outfile);

  if (fseek (pch_outfile, 0, SEEK_SET) != 0
      || fwrite (get_ident (), IDENT_LENGTH, 1, pch_outfile) != 1)
    fatal_error ("can't write %s: %m", pch_file);

  fclose (pch_outfile);
}

/* Check the PCH file called NAME, open on FD, to see if it can be
   used in this compilation.  Return 1 if valid, 0 if the file can't
   be used now but might be if it's seen later in the compilation, and
   2 if this file could never be used in the compilation.  */

int
c_common_valid_pch (cpp_reader *pfile, const char *name, int fd)
{
  int sizeread;
  int result;
  char ident[IDENT_LENGTH];
  char short_strings[256 * 3];
  int strings_length;
  const char *pch_ident;
  struct c_pch_validity v;
  unsigned int current_flags_info = 0;

  if (flag_unit_at_a_time)
    current_flags_info |= FLAG_UNIT_AT_A_TIME_SET;

  /* Perform a quick test of whether this is a valid
     precompiled header for the current language
     and with the current flag settings.  */

  sizeread = read (fd, ident, IDENT_LENGTH);
  if (sizeread == -1)
    fatal_error ("can't read %s: %m", name);
  else if (sizeread != IDENT_LENGTH)
    return 2;
  
  pch_ident = get_ident();
  if (memcmp (ident, pch_ident, IDENT_LENGTH) != 0)
    {
      if (cpp_get_options (pfile)->warn_invalid_pch)
	{
	  if (memcmp (ident, pch_ident, 5) == 0)
	    /* It's a PCH, for the right language, but has the wrong version.
	     */
	    cpp_error (pfile, CPP_DL_WARNING, 
		       "%s: not compatible with this GCC version", name);
	  else if (memcmp (ident, pch_ident, 4) == 0)
	    /* It's a PCH for the wrong language.  */
	    cpp_error (pfile, CPP_DL_WARNING, "%s: not for %s", name,
		       lang_hooks.name);
	  else 
	    /* Not any kind of PCH.  */
	    cpp_error (pfile, CPP_DL_WARNING, "%s: not a PCH file", name);
	}
      return 2;
    }

  /* At this point, we know it's a PCH file, so it ought to be long enough
     that we can read a c_pch_validity structure.  */
  if (read (fd, &v, sizeof (v)) != sizeof (v))
    fatal_error ("can't read %s: %m", name);

  strings_length = (v.host_machine_length + v.target_machine_length 
		    + v.version_length);
  if (read (fd, short_strings, strings_length) != strings_length)
    fatal_error ("can't read %s: %m", name);
  if (v.host_machine_length != strlen (host_machine)
      || memcmp (host_machine, short_strings, strlen (host_machine)) != 0)
    {
      if (cpp_get_options (pfile)->warn_invalid_pch)
	cpp_error (pfile, CPP_DL_WARNING, 
		   "%s: created on host `%.*s', but used on host `%s'", name,
		   v.host_machine_length, short_strings, host_machine);
      return 2;
    }
  if (v.target_machine_length != strlen (target_machine)
      || memcmp (target_machine, short_strings + v.host_machine_length,
		 strlen (target_machine)) != 0)
    {
      if (cpp_get_options (pfile)->warn_invalid_pch)
	cpp_error (pfile, CPP_DL_WARNING, 
		   "%s: created for target `%.*s', but used for target `%s'", 
		   name, v.target_machine_length, 
		   short_strings + v.host_machine_length, target_machine);
      return 2;
    }
  if (v.version_length != strlen (version_string)
      || memcmp (version_string, 
		 (short_strings + v.host_machine_length 
		  + v.target_machine_length),
		 v.version_length) != 0)
    {
      if (cpp_get_options (pfile)->warn_invalid_pch)
	cpp_error (pfile, CPP_DL_WARNING,
		   "%s: created by version `%.*s', but this is version `%s'", 
		   name, v.version_length, 
		   (short_strings + v.host_machine_length 
		    + v.target_machine_length), 
		   version_string);
      return 2;
    }
  if (v.flags_info != current_flags_info)
    {
      if (cpp_get_options (pfile)->warn_invalid_pch)
	cpp_error (pfile, CPP_DL_WARNING,
		   "%s: created using different flags",
		   name);
      return 2;
    }

  /* The allowable debug info combinations are that either the PCH file
     was built with the same as is being used now, or the PCH file was
     built for some kind of debug info but now none is in use.  */
  if (v.debug_info_type != write_symbols
      && write_symbols != NO_DEBUG)
    {
      if (cpp_get_options (pfile)->warn_invalid_pch)
	cpp_error (pfile, CPP_DL_WARNING, 
		   "%s: created with -g%s, but used with -g%s", name,
		   debug_type_names[v.debug_info_type],
		   debug_type_names[write_symbols]);
      return 2;
    }

  /* If the text segment was not loaded at the same address as it was
     when the PCH file was created, function pointers loaded from the
     PCH will not be valid.  We could in theory remap all the function
     pointers, but no support for that exists at present.  */
  if (v.pch_init != &pch_init)
    {
      if (cpp_get_options (pfile)->warn_invalid_pch)
	cpp_error (pfile, CPP_DL_WARNING, 
		   "%s: had text segment at different address", name);
      return 2;
    }

  /* Check the target-specific validity data.  */
  {
    void *this_file_data = xmalloc (v.target_data_length);
    const char *msg;
    
    if ((size_t) read (fd, this_file_data, v.target_data_length)
	!= v.target_data_length)
      fatal_error ("can't read %s: %m", name);
    msg = targetm.pch_valid_p (this_file_data, v.target_data_length);
    free (this_file_data);
    if (msg != NULL)
      {
	if (cpp_get_options (pfile)->warn_invalid_pch)
	  cpp_error (pfile, CPP_DL_WARNING, "%s: %s", name, msg);
	return 2;
      }
  }

  /* Check the preprocessor macros are the same as when the PCH was
     generated.  */
  
  result = cpp_valid_state (pfile, name, fd);
  if (result == -1)
    return 2;
  else
    return result == 0;
}

/* Load in the PCH file NAME, open on FD.  It was originally searched for
   by ORIG_NAME.  */

void
c_common_read_pch (cpp_reader *pfile, const char *name,
		   int fd, const char *orig_name ATTRIBUTE_UNUSED)
{
  FILE *f;
  struct c_pch_header h;
  char *buf;
  unsigned long written;
  struct save_macro_data *smd;
  
  f = fdopen (fd, "rb");
  if (f == NULL)
    {
      cpp_errno (pfile, CPP_DL_ERROR, "calling fdopen");
      return;
    }

  cpp_get_callbacks (parse_in)->valid_pch = NULL;

  if (fread (&h, sizeof (h), 1, f) != 1)
    {
      cpp_errno (pfile, CPP_DL_ERROR, "reading");
      return;
    }

  buf = xmalloc (16384);
  for (written = 0; written < h.asm_size; )
    {
      long size = h.asm_size - written;
      if (size > 16384)
	size = 16384;
      if (fread (buf, size, 1, f) != 1
	  || fwrite (buf, size, 1, asm_out_file) != 1)
	cpp_errno (pfile, CPP_DL_ERROR, "reading");
      written += size;
    }
  free (buf);

  cpp_prepare_state (pfile, &smd);

  gt_pch_restore (f);

  if (cpp_read_state (pfile, name, f, smd) != 0)
    return;

  fclose (f);
}

/* Indicate that no more PCH files should be read.  */

void
c_common_no_more_pch (void)
{
  if (cpp_get_callbacks (parse_in)->valid_pch)
    {
      cpp_get_callbacks (parse_in)->valid_pch = NULL;
      host_hooks.gt_pch_use_address (NULL, 0);
    }
}