gcc/c-family/c-pch.c

   1 /* Precompiled header implementation for the C languages.
   2    Copyright (C) 2000-2017 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 "target.h"
  24 #include "c-common.h"
  25 #include "timevar.h"
  26 #include "flags.h"
  27 #include "debug.h"
  28 #include "c-pragma.h"
  29 #include "langhooks.h"
  30 #include "hosthooks.h"
  31
  32 /* This is a list of flag variables that must match exactly, and their
  33    names for the error message.  The possible values for *flag_var must
  34    fit in a 'signed char'.  */
  35
  36 static const struct c_pch_matching
  37 {
  38   int *flag_var;
  39   const char *flag_name;
  40 } pch_matching[] = {
  41   { &flag_exceptions, "-fexceptions" },
  42 };
  43
  44 enum {
  45   MATCH_SIZE = ARRAY_SIZE (pch_matching)
  46 };
  47
  48 /* The value of the checksum in the dummy compiler that is actually
  49    checksummed.  That compiler should never be run.  */
  50 static const char no_checksum[16] = { 0 };
  51
  52 /* Information about flags and suchlike that affect PCH validity.
  53
  54    Before this structure is read, both an initial 8-character identification
  55    string, and a 16-byte checksum, have been read and validated.  */
  56
  57 struct c_pch_validity
  58 {
  59   unsigned char debug_info_type;
  60   signed char match[MATCH_SIZE];
  61   void (*pch_init) (void);
  62   size_t target_data_length;
  63 };
  64
  65 #define IDENT_LENGTH 8
  66
  67 /* The file we'll be writing the PCH to.  */
  68 static FILE *pch_outfile;
  69
  70 static const char *get_ident (void);
  71
  72 /* Compute an appropriate 8-byte magic number for the PCH file, so that
  73    utilities like file(1) can identify it, and so that GCC can quickly
  74    ignore non-PCH files and PCH files that are of a completely different
  75    format.  */
  76
  77 static const char *
  78 get_ident (void)
  79 {
  80   static char result[IDENT_LENGTH];
  81   static const char templ[] = "gpch.014";
  82   static const char c_language_chars[] = "Co+O";
  83
  84   memcpy (result, templ, IDENT_LENGTH);
  85   result[4] = c_language_chars[c_language];
  86
  87   return result;
  88 }
  89
  90 /* Whether preprocessor state should be saved by pch_init.  */
  91
  92 static bool pch_ready_to_save_cpp_state = false;
  93
  94 /* Prepare to write a PCH file, if one is being written.  This is
  95    called at the start of compilation.  */
  96
  97 void
  98 pch_init (void)
  99 {
 100   FILE *f;
 101   struct c_pch_validity v;
 102   void *target_validity;
 103   static const char partial_pch[] = "gpcWrite";
 104
 105   if (!pch_file)
 106     return;
 107
 108   f = fopen (pch_file, "w+b");
 109   if (f == NULL)
 110     fatal_error (input_location, "can%'t create precompiled header %s: %m",
 111                  pch_file);
 112   pch_outfile = f;
 113
 114   gcc_assert (memcmp (executable_checksum, no_checksum, 16) != 0);
 115
 116   memset (&v, '\0', sizeof (v));
 117   v.debug_info_type = write_symbols;
 118   {
 119     size_t i;
 120     for (i = 0; i < MATCH_SIZE; i++)
 121       {
 122         v.match[i] = *pch_matching[i].flag_var;
 123         gcc_assert (v.match[i] == *pch_matching[i].flag_var);
 124       }
 125   }
 126   v.pch_init = &pch_init;
 127   target_validity = targetm.get_pch_validity (&v.target_data_length);
 128
 129   if (fwrite (partial_pch, IDENT_LENGTH, 1, f) != 1
 130       || fwrite (executable_checksum, 16, 1, f) != 1
 131       || fwrite (&v, sizeof (v), 1, f) != 1
 132       || fwrite (target_validity, v.target_data_length, 1, f) != 1)
 133     fatal_error (input_location, "can%'t write to %s: %m", pch_file);
 134
 135   /* Let the debugging format deal with the PCHness.  */
 136   (*debug_hooks->handle_pch) (0);
 137
 138   if (pch_ready_to_save_cpp_state)
 139     pch_cpp_save_state ();
 140
 141   XDELETE (target_validity);
 142 }
 143
 144 /* Whether preprocessor state has been saved in a PCH file.  */
 145
 146 static bool pch_cpp_state_saved = false;
 147
 148 /* Save preprocessor state in a PCH file, after implicitly included
 149    headers have been read.  If the PCH file has not yet been opened,
 150    record that state should be saved when it is opened.  */
 151
 152 void
 153 pch_cpp_save_state (void)
 154 {
 155   if (!pch_cpp_state_saved)
 156     {
 157       if (pch_outfile)
 158         {
 159           cpp_save_state (parse_in, pch_outfile);
 160           pch_cpp_state_saved = true;
 161         }
 162       else
 163         pch_ready_to_save_cpp_state = true;
 164     }
 165 }
 166
 167 /* Write the PCH file.  This is called at the end of a compilation which
 168    will produce a PCH file.  */
 169
 170 void
 171 c_common_write_pch (void)
 172 {
 173   timevar_push (TV_PCH_SAVE);
 174
 175   targetm.prepare_pch_save ();
 176
 177   (*debug_hooks->handle_pch) (1);
 178
 179   prepare_target_option_nodes_for_pch ();
 180
 181   cpp_write_pch_deps (parse_in, pch_outfile);
 182
 183   gt_pch_save (pch_outfile);
 184
 185   timevar_push (TV_PCH_CPP_SAVE);
 186   cpp_write_pch_state (parse_in, pch_outfile);
 187   timevar_pop (TV_PCH_CPP_SAVE);
 188
 189   if (fseek (pch_outfile, 0, SEEK_SET) != 0
 190       || fwrite (get_ident (), IDENT_LENGTH, 1, pch_outfile) != 1)
 191     fatal_error (input_location, "can%'t write %s: %m", pch_file);
 192
 193   fclose (pch_outfile);
 194
 195   timevar_pop (TV_PCH_SAVE);
 196 }
 197
 198 /* Check the PCH file called NAME, open on FD, to see if it can be
 199    used in this compilation.  Return 1 if valid, 0 if the file can't
 200    be used now but might be if it's seen later in the compilation, and
 201    2 if this file could never be used in the compilation.  */
 202
 203 int
 204 c_common_valid_pch (cpp_reader *pfile, const char *name, int fd)
 205 {
 206   int sizeread;
 207   int result;
 208   char ident[IDENT_LENGTH + 16];
 209   const char *pch_ident;
 210   struct c_pch_validity v;
 211
 212   /* Perform a quick test of whether this is a valid
 213      precompiled header for the current language.  */
 214
 215   gcc_assert (memcmp (executable_checksum, no_checksum, 16) != 0);
 216
 217   sizeread = read (fd, ident, IDENT_LENGTH + 16);
 218   if (sizeread == -1)
 219     fatal_error (input_location, "can%'t read %s: %m", name);
 220   else if (sizeread != IDENT_LENGTH + 16)
 221     {
 222       if (cpp_get_options (pfile)->warn_invalid_pch)
 223         cpp_error (pfile, CPP_DL_WARNING, "%s: too short to be a PCH file",
 224                    name);
 225       return 2;
 226     }
 227
 228   pch_ident = get_ident();
 229   if (memcmp (ident, pch_ident, IDENT_LENGTH) != 0)
 230     {
 231       if (cpp_get_options (pfile)->warn_invalid_pch)
 232         {
 233           if (memcmp (ident, pch_ident, 5) == 0)
 234             /* It's a PCH, for the right language, but has the wrong version.
 235              */
 236             cpp_error (pfile, CPP_DL_WARNING,
 237                        "%s: not compatible with this GCC version", name);
 238           else if (memcmp (ident, pch_ident, 4) == 0)
 239             /* It's a PCH for the wrong language.  */
 240             cpp_error (pfile, CPP_DL_WARNING, "%s: not for %s", name,
 241                        lang_hooks.name);
 242           else
 243             /* Not any kind of PCH.  */
 244             cpp_error (pfile, CPP_DL_WARNING, "%s: not a PCH file", name);
 245         }
 246       return 2;
 247     }
 248   if (memcmp (ident + IDENT_LENGTH, executable_checksum, 16) != 0)
 249     {
 250       if (cpp_get_options (pfile)->warn_invalid_pch)
 251         cpp_error (pfile, CPP_DL_WARNING,
 252                    "%s: created by a different GCC executable", name);
 253       return 2;
 254     }
 255
 256   /* At this point, we know it's a PCH file created by this
 257      executable, so it ought to be long enough that we can read a
 258      c_pch_validity structure.  */
 259   if (read (fd, &v, sizeof (v)) != sizeof (v))
 260     fatal_error (input_location, "can%'t read %s: %m", name);
 261
 262   /* The allowable debug info combinations are that either the PCH file
 263      was built with the same as is being used now, or the PCH file was
 264      built for some kind of debug info but now none is in use.  */
 265   if (v.debug_info_type != write_symbols
 266       && write_symbols != NO_DEBUG)
 267     {
 268       if (cpp_get_options (pfile)->warn_invalid_pch)
 269         cpp_error (pfile, CPP_DL_WARNING,
 270                    "%s: created with -g%s, but used with -g%s", name,
 271                    debug_type_names[v.debug_info_type],
 272                    debug_type_names[write_symbols]);
 273       return 2;
 274     }
 275
 276   /* Check flags that must match exactly.  */
 277   {
 278     size_t i;
 279     for (i = 0; i < MATCH_SIZE; i++)
 280       if (*pch_matching[i].flag_var != v.match[i])
 281         {
 282           if (cpp_get_options (pfile)->warn_invalid_pch)
 283             cpp_error (pfile, CPP_DL_WARNING,
 284                        "%s: settings for %s do not match", name,
 285                        pch_matching[i].flag_name);
 286           return 2;
 287         }
 288   }
 289
 290   /* If the text segment was not loaded at the same address as it was
 291      when the PCH file was created, function pointers loaded from the
 292      PCH will not be valid.  We could in theory remap all the function
 293      pointers, but no support for that exists at present.
 294      Since we have the same executable, it should only be necessary to
 295      check one function.  */
 296   if (v.pch_init != &pch_init)
 297     {
 298       if (cpp_get_options (pfile)->warn_invalid_pch)
 299         cpp_error (pfile, CPP_DL_WARNING,
 300                    "%s: had text segment at different address", name);
 301       return 2;
 302     }
 303
 304   /* Check the target-specific validity data.  */
 305   {
 306     void *this_file_data = xmalloc (v.target_data_length);
 307     const char *msg;
 308
 309     if ((size_t) read (fd, this_file_data, v.target_data_length)
 310         != v.target_data_length)
 311       fatal_error (input_location, "can%'t read %s: %m", name);
 312     msg = targetm.pch_valid_p (this_file_data, v.target_data_length);
 313     free (this_file_data);
 314     if (msg != NULL)
 315       {
 316         if (cpp_get_options (pfile)->warn_invalid_pch)
 317           cpp_error (pfile, CPP_DL_WARNING, "%s: %s", name, msg);
 318         return 2;
 319       }
 320   }
 321
 322   /* Check the preprocessor macros are the same as when the PCH was
 323      generated.  */
 324
 325   result = cpp_valid_state (pfile, name, fd);
 326   if (result == -1)
 327     return 2;
 328   else
 329     return result == 0;
 330 }
 331
 332 /* If non-NULL, this function is called after a precompile header file
 333    is loaded.  */
 334 void (*lang_post_pch_load) (void);
 335
 336 /* Load in the PCH file NAME, open on FD.  It was originally searched for
 337    by ORIG_NAME.  */
 338
 339 void
 340 c_common_read_pch (cpp_reader *pfile, const char *name,
 341                    int fd, const char *orig_name ATTRIBUTE_UNUSED)
 342 {
 343   FILE *f;
 344   struct save_macro_data *smd;
 345   expanded_location saved_loc;
 346   bool saved_trace_includes;
 347
 348   timevar_push (TV_PCH_RESTORE);
 349
 350   f = fdopen (fd, "rb");
 351   if (f == NULL)
 352     {
 353       cpp_errno (pfile, CPP_DL_ERROR, "calling fdopen");
 354       close (fd);
 355       goto end;
 356     }
 357
 358   cpp_get_callbacks (parse_in)->valid_pch = NULL;
 359
 360   /* Save the location and then restore it after reading the PCH.  */
 361   saved_loc = expand_location (line_table->highest_line);
 362   saved_trace_includes = line_table->trace_includes;
 363
 364   timevar_push (TV_PCH_CPP_RESTORE);
 365   cpp_prepare_state (pfile, &smd);
 366   timevar_pop (TV_PCH_CPP_RESTORE);
 367
 368   gt_pch_restore (f);
 369   cpp_set_line_map (pfile, line_table);
 370   rebuild_location_adhoc_htab (line_table);
 371
 372   timevar_push (TV_PCH_CPP_RESTORE);
 373   if (cpp_read_state (pfile, name, f, smd) != 0)
 374     {
 375       fclose (f);
 376       timevar_pop (TV_PCH_CPP_RESTORE);
 377       goto end;
 378     }
 379   timevar_pop (TV_PCH_CPP_RESTORE);
 380
 381
 382   fclose (f);
 383
 384   line_table->trace_includes = saved_trace_includes;
 385   linemap_add (line_table, LC_ENTER, 0, saved_loc.file, saved_loc.line);
 386
 387   /* Give the front end a chance to take action after a PCH file has
 388      been loaded.  */
 389   if (lang_post_pch_load)
 390     (*lang_post_pch_load) ();
 391
 392 end:
 393   timevar_pop (TV_PCH_RESTORE);
 394 }
 395
 396 /* Indicate that no more PCH files should be read.  */
 397
 398 void
 399 c_common_no_more_pch (void)
 400 {
 401   if (cpp_get_callbacks (parse_in)->valid_pch)
 402     {
 403       cpp_get_callbacks (parse_in)->valid_pch = NULL;
 404       host_hooks.gt_pch_use_address (NULL, 0, -1, 0);
 405     }
 406 }
 407
 408 /* Handle #pragma GCC pch_preprocess, to load in the PCH file.  */
 409
 410 void
 411 c_common_pch_pragma (cpp_reader *pfile, const char *name)
 412 {
 413   int fd;
 414
 415   if (!cpp_get_options (pfile)->preprocessed)
 416     {
 417       error ("pch_preprocess pragma should only be used with -fpreprocessed");
 418       inform (input_location, "use #include instead");
 419       return;
 420     }
 421
 422   fd = open (name, O_RDONLY | O_BINARY, 0666);
 423   if (fd == -1)
 424     fatal_error (input_location, "%s: couldn%'t open PCH file: %m", name);
 425
 426   if (c_common_valid_pch (pfile, name, fd) != 1)
 427     {
 428       if (!cpp_get_options (pfile)->warn_invalid_pch)
 429         inform (input_location, "use -Winvalid-pch for more information");
 430       fatal_error (input_location, "%s: PCH file was invalid", name);
 431     }
 432
 433   c_common_read_pch (pfile, name, fd, name);
 434
 435   close (fd);
 436 }
 437