gcc/c-pch.c

   1 /* Precompiled header implementation for the C languages.
   2    Copyright (C) 2000, 2002, 2003, 2004, 2005, 2007 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 3, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #include "config.h"
  21 #include "system.h"
  22 #include "coretypes.h"
  23 #include "version.h"
  24 #include "cpplib.h"
  25 #include "tree.h"
  26 #include "flags.h"
  27 #include "c-common.h"
  28 #include "output.h"
  29 #include "toplev.h"
  30 #include "debug.h"
  31 #include "c-pragma.h"
  32 #include "ggc.h"
  33 #include "langhooks.h"
  34 #include "hosthooks.h"
  35 #include "target.h"
  36
  37 /* This is a list of flag variables that must match exactly, and their
  38    names for the error message.  The possible values for *flag_var must
  39    fit in a 'signed char'.  */
  40
  41 static const struct c_pch_matching
  42 {
  43   int *flag_var;
  44   const char *flag_name;
  45 } pch_matching[] = {
  46   { &flag_exceptions, "-fexceptions" },
  47   { &flag_unit_at_a_time, "-funit-at-a-time" }
  48 };
  49
  50 enum {
  51   MATCH_SIZE = ARRAY_SIZE (pch_matching)
  52 };
  53
  54 /* The value of the checksum in the dummy compiler that is actually
  55    checksummed.  That compiler should never be run.  */
  56 static const char no_checksum[16] = { 0 };
  57
  58 /* Information about flags and suchlike that affect PCH validity.
  59
  60    Before this structure is read, both an initial 8-character identification
  61    string, and a 16-byte checksum, have been read and validated.  */
  62
  63 struct c_pch_validity
  64 {
  65   unsigned char debug_info_type;
  66   signed char match[MATCH_SIZE];
  67   void (*pch_init) (void);
  68   size_t target_data_length;
  69 };
  70
  71 struct c_pch_header
  72 {
  73   unsigned long asm_size;
  74 };
  75
  76 #define IDENT_LENGTH 8
  77
  78 /* The file we'll be writing the PCH to.  */
  79 static FILE *pch_outfile;
  80
  81 /* The position in the assembler output file when pch_init was called.  */
  82 static long asm_file_startpos;
  83
  84 static const char *get_ident (void);
  85
  86 /* Compute an appropriate 8-byte magic number for the PCH file, so that
  87    utilities like file(1) can identify it, and so that GCC can quickly
  88    ignore non-PCH files and PCH files that are of a completely different
  89    format.  */
  90
  91 static const char *
  92 get_ident (void)
  93 {
  94   static char result[IDENT_LENGTH];
  95   static const char template[IDENT_LENGTH] = "gpch.013";
  96   static const char c_language_chars[] = "Co+O";
  97
  98   memcpy (result, template, IDENT_LENGTH);
  99   result[4] = c_language_chars[c_language];
 100
 101   return result;
 102 }
 103
 104 /* Prepare to write a PCH file, if one is being written.  This is
 105    called at the start of compilation.
 106
 107    Also, print out the executable checksum if -fverbose-asm is in effect.  */
 108
 109 void
 110 pch_init (void)
 111 {
 112   FILE *f;
 113   struct c_pch_validity v;
 114   void *target_validity;
 115   static const char partial_pch[IDENT_LENGTH] = "gpcWrite";
 116
 117 #ifdef ASM_COMMENT_START
 118   if (flag_verbose_asm)
 119     {
 120       fprintf (asm_out_file, "%s ", ASM_COMMENT_START);
 121       c_common_print_pch_checksum (asm_out_file);
 122       fputc ('\n', asm_out_file);
 123     }
 124 #endif
 125
 126   if (!pch_file)
 127     return;
 128
 129   f = fopen (pch_file, "w+b");
 130   if (f == NULL)
 131     fatal_error ("can%'t create precompiled header %s: %m", pch_file);
 132   pch_outfile = f;
 133
 134   gcc_assert (memcmp (executable_checksum, no_checksum, 16) != 0);
 135
 136   v.debug_info_type = write_symbols;
 137   {
 138     size_t i;
 139     for (i = 0; i < MATCH_SIZE; i++)
 140       {
 141         v.match[i] = *pch_matching[i].flag_var;
 142         gcc_assert (v.match[i] == *pch_matching[i].flag_var);
 143       }
 144   }
 145   v.pch_init = &pch_init;
 146   target_validity = targetm.get_pch_validity (&v.target_data_length);
 147
 148   if (fwrite (partial_pch, IDENT_LENGTH, 1, f) != 1
 149       || fwrite (executable_checksum, 16, 1, f) != 1
 150       || fwrite (&v, sizeof (v), 1, f) != 1
 151       || fwrite (target_validity, v.target_data_length, 1, f) != 1)
 152     fatal_error ("can%'t write to %s: %m", pch_file);
 153
 154   /* We need to be able to re-read the output.  */
 155   /* The driver always provides a valid -o option.  */
 156   if (asm_file_name == NULL
 157       || strcmp (asm_file_name, "-") == 0)
 158     fatal_error ("%qs is not a valid output file", asm_file_name);
 159
 160   asm_file_startpos = ftell (asm_out_file);
 161
 162   /* Let the debugging format deal with the PCHness.  */
 163   (*debug_hooks->handle_pch) (0);
 164
 165   cpp_save_state (parse_in, f);
 166 }
 167
 168 /* Write the PCH file.  This is called at the end of a compilation which
 169    will produce a PCH file.  */
 170
 171 void
 172 c_common_write_pch (void)
 173 {
 174   char *buf;
 175   long asm_file_end;
 176   long written;
 177   struct c_pch_header h;
 178
 179   (*debug_hooks->handle_pch) (1);
 180
 181   cpp_write_pch_deps (parse_in, pch_outfile);
 182
 183   asm_file_end = ftell (asm_out_file);
 184   h.asm_size = asm_file_end - asm_file_startpos;
 185
 186   if (fwrite (&h, sizeof (h), 1, pch_outfile) != 1)
 187     fatal_error ("can%'t write %s: %m", pch_file);
 188
 189   buf = XNEWVEC (char, 16384);
 190
 191   if (fseek (asm_out_file, asm_file_startpos, SEEK_SET) != 0)
 192     fatal_error ("can%'t seek in %s: %m", asm_file_name);
 193
 194   for (written = asm_file_startpos; written < asm_file_end; )
 195     {
 196       long size = asm_file_end - written;
 197       if (size > 16384)
 198         size = 16384;
 199       if (fread (buf, size, 1, asm_out_file) != 1)
 200         fatal_error ("can%'t read %s: %m", asm_file_name);
 201       if (fwrite (buf, size, 1, pch_outfile) != 1)
 202         fatal_error ("can%'t write %s: %m", pch_file);
 203       written += size;
 204     }
 205   free (buf);
 206   /* asm_out_file can be written afterwards, so fseek to clear
 207      _IOREAD flag.  */
 208   if (fseek (asm_out_file, 0, SEEK_END) != 0)
 209     fatal_error ("can%'t seek in %s: %m", asm_file_name);
 210
 211   gt_pch_save (pch_outfile);
 212   cpp_write_pch_state (parse_in, pch_outfile);
 213
 214   if (fseek (pch_outfile, 0, SEEK_SET) != 0
 215       || fwrite (get_ident (), IDENT_LENGTH, 1, pch_outfile) != 1)
 216     fatal_error ("can%'t write %s: %m", pch_file);
 217
 218   fclose (pch_outfile);
 219 }
 220
 221 /* Check the PCH file called NAME, open on FD, to see if it can be
 222    used in this compilation.  Return 1 if valid, 0 if the file can't
 223    be used now but might be if it's seen later in the compilation, and
 224    2 if this file could never be used in the compilation.  */
 225
 226 int
 227 c_common_valid_pch (cpp_reader *pfile, const char *name, int fd)
 228 {
 229   int sizeread;
 230   int result;
 231   char ident[IDENT_LENGTH + 16];
 232   const char *pch_ident;
 233   struct c_pch_validity v;
 234
 235   /* Perform a quick test of whether this is a valid
 236      precompiled header for the current language.  */
 237
 238   gcc_assert (memcmp (executable_checksum, no_checksum, 16) != 0);
 239
 240   sizeread = read (fd, ident, IDENT_LENGTH + 16);
 241   if (sizeread == -1)
 242     fatal_error ("can%'t read %s: %m", name);
 243   else if (sizeread != IDENT_LENGTH + 16)
 244     {
 245       cpp_error (pfile, CPP_DL_WARNING, "%s: too short to be a PCH file",
 246                  name);
 247       return 2;
 248     }
 249
 250   pch_ident = get_ident();
 251   if (memcmp (ident, pch_ident, IDENT_LENGTH) != 0)
 252     {
 253       if (cpp_get_options (pfile)->warn_invalid_pch)
 254         {
 255           if (memcmp (ident, pch_ident, 5) == 0)
 256             /* It's a PCH, for the right language, but has the wrong version.
 257              */
 258             cpp_error (pfile, CPP_DL_WARNING,
 259                        "%s: not compatible with this GCC version", name);
 260           else if (memcmp (ident, pch_ident, 4) == 0)
 261             /* It's a PCH for the wrong language.  */
 262             cpp_error (pfile, CPP_DL_WARNING, "%s: not for %s", name,
 263                        lang_hooks.name);
 264           else
 265             /* Not any kind of PCH.  */
 266             cpp_error (pfile, CPP_DL_WARNING, "%s: not a PCH file", name);
 267         }
 268       return 2;
 269     }
 270   if (memcmp (ident + IDENT_LENGTH, executable_checksum, 16) != 0)
 271     {
 272       if (cpp_get_options (pfile)->warn_invalid_pch)
 273         cpp_error (pfile, CPP_DL_WARNING,
 274                    "%s: created by a different GCC executable", name);
 275       return 2;
 276     }
 277
 278   /* At this point, we know it's a PCH file created by this
 279      executable, so it ought to be long enough that we can read a
 280      c_pch_validity structure.  */
 281   if (read (fd, &v, sizeof (v)) != sizeof (v))
 282     fatal_error ("can%'t read %s: %m", name);
 283
 284   /* The allowable debug info combinations are that either the PCH file
 285      was built with the same as is being used now, or the PCH file was
 286      built for some kind of debug info but now none is in use.  */
 287   if (v.debug_info_type != write_symbols
 288       && write_symbols != NO_DEBUG)
 289     {
 290       if (cpp_get_options (pfile)->warn_invalid_pch)
 291         cpp_error (pfile, CPP_DL_WARNING,
 292                    "%s: created with -g%s, but used with -g%s", name,
 293                    debug_type_names[v.debug_info_type],
 294                    debug_type_names[write_symbols]);
 295       return 2;
 296     }
 297
 298   /* Check flags that must match exactly.  */
 299   {
 300     size_t i;
 301     for (i = 0; i < MATCH_SIZE; i++)
 302       if (*pch_matching[i].flag_var != v.match[i])
 303         {
 304           if (cpp_get_options (pfile)->warn_invalid_pch)
 305             cpp_error (pfile, CPP_DL_WARNING,
 306                        "%s: settings for %s do not match", name,
 307                        pch_matching[i].flag_name);
 308           return 2;
 309         }
 310   }
 311
 312   /* If the text segment was not loaded at the same address as it was
 313      when the PCH file was created, function pointers loaded from the
 314      PCH will not be valid.  We could in theory remap all the function
 315      pointers, but no support for that exists at present.
 316      Since we have the same executable, it should only be necessary to
 317      check one function.  */
 318   if (v.pch_init != &pch_init)
 319     {
 320       if (cpp_get_options (pfile)->warn_invalid_pch)
 321         cpp_error (pfile, CPP_DL_WARNING,
 322                    "%s: had text segment at different address", name);
 323       return 2;
 324     }
 325
 326   /* Check the target-specific validity data.  */
 327   {
 328     void *this_file_data = xmalloc (v.target_data_length);
 329     const char *msg;
 330
 331     if ((size_t) read (fd, this_file_data, v.target_data_length)
 332         != v.target_data_length)
 333       fatal_error ("can%'t read %s: %m", name);
 334     msg = targetm.pch_valid_p (this_file_data, v.target_data_length);
 335     free (this_file_data);
 336     if (msg != NULL)
 337       {
 338         if (cpp_get_options (pfile)->warn_invalid_pch)
 339           cpp_error (pfile, CPP_DL_WARNING, "%s: %s", name, msg);
 340         return 2;
 341       }
 342   }
 343
 344   /* Check the preprocessor macros are the same as when the PCH was
 345      generated.  */
 346
 347   result = cpp_valid_state (pfile, name, fd);
 348   if (result == -1)
 349     return 2;
 350   else
 351     return result == 0;
 352 }
 353
 354 /* If non-NULL, this function is called after a precompile header file
 355    is loaded.  */
 356 void (*lang_post_pch_load) (void);
 357
 358 /* Load in the PCH file NAME, open on FD.  It was originally searched for
 359    by ORIG_NAME.  */
 360
 361 void
 362 c_common_read_pch (cpp_reader *pfile, const char *name,
 363                    int fd, const char *orig_name ATTRIBUTE_UNUSED)
 364 {
 365   FILE *f;
 366   struct c_pch_header h;
 367   struct save_macro_data *smd;
 368
 369   f = fdopen (fd, "rb");
 370   if (f == NULL)
 371     {
 372       cpp_errno (pfile, CPP_DL_ERROR, "calling fdopen");
 373       return;
 374     }
 375
 376   cpp_get_callbacks (parse_in)->valid_pch = NULL;
 377
 378   if (fread (&h, sizeof (h), 1, f) != 1)
 379     {
 380       cpp_errno (pfile, CPP_DL_ERROR, "reading");
 381       return;
 382     }
 383
 384   if (!flag_preprocess_only)
 385     {
 386       unsigned long written;
 387       char * buf = XNEWVEC (char, 16384);
 388
 389       for (written = 0; written < h.asm_size; )
 390         {
 391           long size = h.asm_size - written;
 392           if (size > 16384)
 393             size = 16384;
 394           if (fread (buf, size, 1, f) != 1
 395               || fwrite (buf, size, 1, asm_out_file) != 1)
 396             cpp_errno (pfile, CPP_DL_ERROR, "reading");
 397           written += size;
 398         }
 399       free (buf);
 400     }
 401   else
 402     {
 403       /* If we're preprocessing, don't write to a NULL
 404          asm_out_file.  */
 405       if (fseek (f, h.asm_size, SEEK_CUR) != 0)
 406         cpp_errno (pfile, CPP_DL_ERROR, "seeking");
 407     }
 408
 409   cpp_prepare_state (pfile, &smd);
 410
 411   gt_pch_restore (f);
 412
 413   if (cpp_read_state (pfile, name, f, smd) != 0)
 414     return;
 415
 416   fclose (f);
 417
 418   /* Give the front end a chance to take action after a PCH file has
 419      been loaded.  */
 420   if (lang_post_pch_load)
 421     (*lang_post_pch_load) ();
 422 }
 423
 424 /* Indicate that no more PCH files should be read.  */
 425
 426 void
 427 c_common_no_more_pch (void)
 428 {
 429   if (cpp_get_callbacks (parse_in)->valid_pch)
 430     {
 431       cpp_get_callbacks (parse_in)->valid_pch = NULL;
 432       host_hooks.gt_pch_use_address (NULL, 0, -1, 0);
 433     }
 434 }
 435
 436 /* Handle #pragma GCC pch_preprocess, to load in the PCH file.  */
 437
 438 #ifndef O_BINARY
 439 # define O_BINARY 0
 440 #endif
 441
 442 void
 443 c_common_pch_pragma (cpp_reader *pfile, const char *name)
 444 {
 445   int fd;
 446
 447   if (!cpp_get_options (pfile)->preprocessed)
 448     {
 449       error ("pch_preprocess pragma should only be used with -fpreprocessed");
 450       inform ("use #include instead");
 451       return;
 452     }
 453
 454   fd = open (name, O_RDONLY | O_BINARY, 0666);
 455   if (fd == -1)
 456     fatal_error ("%s: couldn%'t open PCH file: %m", name);
 457
 458   if (c_common_valid_pch (pfile, name, fd) != 1)
 459     {
 460       if (!cpp_get_options (pfile)->warn_invalid_pch)
 461         inform ("use -Winvalid-pch for more information");
 462       fatal_error ("%s: PCH file was invalid", name);
 463     }
 464
 465   c_common_read_pch (pfile, name, fd, name);
 466
 467   close (fd);
 468 }
 469
 470 /* Print out executable_checksum[].  */
 471
 472 void
 473 c_common_print_pch_checksum (FILE *f)
 474 {
 475   int i;
 476   fputs ("Compiler executable checksum: ", f);
 477   for (i = 0; i < 16; i++)
 478     fprintf (f, "%02x", executable_checksum[i]);
 479   putc ('\n', f);
 480 }