gcc/c-family/c-pch.c

   1 /* Precompiled header implementation for the C languages.
   2    Copyright (C) 2000-2020 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 /* Information about flags and suchlike that affect PCH validity.
  49
  50    Before this structure is read, both an initial 8-character identification
  51    string, and a 16-byte checksum, have been read and validated.  */
  52
  53 struct c_pch_validity
  54 {
  55   unsigned char debug_info_type;
  56   signed char match[MATCH_SIZE];
  57   void (*pch_init) (void);
  58   size_t target_data_length;
  59 };
  60
  61 #define IDENT_LENGTH 8
  62
  63 /* The file we'll be writing the PCH to.  */
  64 static FILE *pch_outfile;
  65
  66 static const char *get_ident (void);
  67
  68 /* Compute an appropriate 8-byte magic number for the PCH file, so that
  69    utilities like file(1) can identify it, and so that GCC can quickly
  70    ignore non-PCH files and PCH files that are of a completely different
  71    format.  */
  72
  73 static const char *
  74 get_ident (void)
  75 {
  76   static char result[IDENT_LENGTH];
  77   static const char templ[] = "gpch.014";
  78   static const char c_language_chars[] = "Co+O";
  79
  80   memcpy (result, templ, IDENT_LENGTH);
  81   result[4] = c_language_chars[c_language];
  82
  83   return result;
  84 }
  85
  86 /* Whether preprocessor state should be saved by pch_init.  */
  87
  88 static bool pch_ready_to_save_cpp_state = false;
  89
  90 /* Prepare to write a PCH file, if one is being written.  This is
  91    called at the start of compilation.  */
  92
  93 void
  94 pch_init (void)
  95 {
  96   FILE *f;
  97   struct c_pch_validity v;
  98   void *target_validity;
  99   static const char partial_pch[] = "gpcWrite";
 100
 101   if (!pch_file)
 102     return;
 103
 104   f = fopen (pch_file, "w+b");
 105   if (f == NULL)
 106     fatal_error (input_location, "cannot create precompiled header %s: %m",
 107                  pch_file);
 108   pch_outfile = f;
 109
 110   memset (&v, '\0', sizeof (v));
 111   v.debug_info_type = write_symbols;
 112   {
 113     size_t i;
 114     for (i = 0; i < MATCH_SIZE; i++)
 115       {
 116         v.match[i] = *pch_matching[i].flag_var;
 117         gcc_assert (v.match[i] == *pch_matching[i].flag_var);
 118       }
 119   }
 120   v.pch_init = &pch_init;
 121   target_validity = targetm.get_pch_validity (&v.target_data_length);
 122
 123   if (fwrite (partial_pch, IDENT_LENGTH, 1, f) != 1
 124       || fwrite (executable_checksum, 16, 1, f) != 1
 125       || fwrite (&v, sizeof (v), 1, f) != 1
 126       || fwrite (target_validity, v.target_data_length, 1, f) != 1)
 127     fatal_error (input_location, "cannot write to %s: %m", pch_file);
 128
 129   /* Let the debugging format deal with the PCHness.  */
 130   (*debug_hooks->handle_pch) (0);
 131
 132   if (pch_ready_to_save_cpp_state)
 133     pch_cpp_save_state ();
 134
 135   XDELETE (target_validity);
 136 }
 137
 138 /* Whether preprocessor state has been saved in a PCH file.  */
 139
 140 static bool pch_cpp_state_saved = false;
 141
 142 /* Save preprocessor state in a PCH file, after implicitly included
 143    headers have been read.  If the PCH file has not yet been opened,
 144    record that state should be saved when it is opened.  */
 145
 146 void
 147 pch_cpp_save_state (void)
 148 {
 149   if (!pch_cpp_state_saved)
 150     {
 151       if (pch_outfile)
 152         {
 153           cpp_save_state (parse_in, pch_outfile);
 154           pch_cpp_state_saved = true;
 155         }
 156       else
 157         pch_ready_to_save_cpp_state = true;
 158     }
 159 }
 160
 161 /* Write the PCH file.  This is called at the end of a compilation which
 162    will produce a PCH file.  */
 163
 164 void
 165 c_common_write_pch (void)
 166 {
 167   timevar_push (TV_PCH_SAVE);
 168
 169   targetm.prepare_pch_save ();
 170
 171   (*debug_hooks->handle_pch) (1);
 172
 173   prepare_target_option_nodes_for_pch ();
 174
 175   cpp_write_pch_deps (parse_in, pch_outfile);
 176
 177   gt_pch_save (pch_outfile);
 178
 179   timevar_push (TV_PCH_CPP_SAVE);
 180   cpp_write_pch_state (parse_in, pch_outfile);
 181   timevar_pop (TV_PCH_CPP_SAVE);
 182
 183   if (fseek (pch_outfile, 0, SEEK_SET) != 0
 184       || fwrite (get_ident (), IDENT_LENGTH, 1, pch_outfile) != 1)
 185     fatal_error (input_location, "cannot write %s: %m", pch_file);
 186
 187   fclose (pch_outfile);
 188
 189   timevar_pop (TV_PCH_SAVE);
 190 }
 191
 192 /* Check the PCH file called NAME, open on FD, to see if it can be
 193    used in this compilation.  Return 1 if valid, 0 if the file can't
 194    be used now but might be if it's seen later in the compilation, and
 195    2 if this file could never be used in the compilation.  */
 196
 197 int
 198 c_common_valid_pch (cpp_reader *pfile, const char *name, int fd)
 199 {
 200   int sizeread;
 201   int result;
 202   char ident[IDENT_LENGTH + 16];
 203   const char *pch_ident;
 204   struct c_pch_validity v;
 205
 206   /* Perform a quick test of whether this is a valid
 207      precompiled header for the current language.  */
 208
 209   /* C++ modules and PCH don't play together.  */
 210   if (flag_modules)
 211     return 2;
 212
 213   sizeread = read (fd, ident, IDENT_LENGTH + 16);
 214   if (sizeread == -1)
 215     fatal_error (input_location, "cannot read %s: %m", name);
 216   else if (sizeread != IDENT_LENGTH + 16)
 217     {
 218       cpp_warning (pfile, CPP_W_INVALID_PCH, "%s: too short to be a PCH file",
 219                    name);
 220       return 2;
 221     }
 222
 223   pch_ident = get_ident();
 224   if (memcmp (ident, pch_ident, IDENT_LENGTH) != 0)
 225     {
 226         if (memcmp (ident, pch_ident, 5) == 0)
 227           /* It's a PCH, for the right language, but has the wrong version.  */
 228           cpp_warning (pfile, CPP_W_INVALID_PCH,
 229                        "%s: not compatible with this GCC version", name);
 230         else if (memcmp (ident, pch_ident, 4) == 0)
 231           /* It's a PCH for the wrong language.  */
 232           cpp_warning (pfile, CPP_W_INVALID_PCH, "%s: not for %s", name,
 233                        lang_hooks.name);
 234         else
 235           /* Not any kind of PCH.  */
 236           cpp_warning (pfile, CPP_W_INVALID_PCH, "%s: not a PCH file", name);
 237       return 2;
 238     }
 239   if (memcmp (ident + IDENT_LENGTH, executable_checksum, 16) != 0)
 240     {
 241       cpp_warning (pfile, CPP_W_INVALID_PCH,
 242                    "%s: created by a different GCC executable", name);
 243       return 2;
 244     }
 245
 246   /* At this point, we know it's a PCH file created by this
 247      executable, so it ought to be long enough that we can read a
 248      c_pch_validity structure.  */
 249   if (read (fd, &v, sizeof (v)) != sizeof (v))
 250     fatal_error (input_location, "cannot read %s: %m", name);
 251
 252   /* The allowable debug info combinations are that either the PCH file
 253      was built with the same as is being used now, or the PCH file was
 254      built for some kind of debug info but now none is in use.  */
 255   if (v.debug_info_type != write_symbols
 256       && write_symbols != NO_DEBUG)
 257     {
 258       cpp_warning (pfile, CPP_W_INVALID_PCH,
 259                    "%s: created with -g%s, but used with -g%s", name,
 260                    debug_type_names[v.debug_info_type],
 261                    debug_type_names[write_symbols]);
 262       return 2;
 263     }
 264
 265   /* Check flags that must match exactly.  */
 266   {
 267     size_t i;
 268     for (i = 0; i < MATCH_SIZE; i++)
 269       if (*pch_matching[i].flag_var != v.match[i])
 270         {
 271           cpp_warning (pfile, CPP_W_INVALID_PCH,
 272                        "%s: settings for %s do not match", name,
 273                        pch_matching[i].flag_name);
 274           return 2;
 275         }
 276   }
 277
 278   /* If the text segment was not loaded at the same address as it was
 279      when the PCH file was created, function pointers loaded from the
 280      PCH will not be valid.  We could in theory remap all the function
 281      pointers, but no support for that exists at present.
 282      Since we have the same executable, it should only be necessary to
 283      check one function.  */
 284   if (v.pch_init != &pch_init)
 285     {
 286       cpp_warning (pfile, CPP_W_INVALID_PCH,
 287                    "%s: had text segment at different address", name);
 288       return 2;
 289     }
 290
 291   /* Check the target-specific validity data.  */
 292   {
 293     void *this_file_data = xmalloc (v.target_data_length);
 294     const char *msg;
 295
 296     if ((size_t) read (fd, this_file_data, v.target_data_length)
 297         != v.target_data_length)
 298       fatal_error (input_location, "cannot read %s: %m", name);
 299     msg = targetm.pch_valid_p (this_file_data, v.target_data_length);
 300     free (this_file_data);
 301     if (msg != NULL)
 302       {
 303         cpp_warning (pfile, CPP_W_INVALID_PCH, "%s: %s", name, msg);
 304         return 2;
 305       }
 306   }
 307
 308   /* Check the preprocessor macros are the same as when the PCH was
 309      generated.  */
 310
 311   result = cpp_valid_state (pfile, name, fd);
 312   if (result == -1)
 313     return 2;
 314   else
 315     return result == 0;
 316 }
 317
 318 /* If non-NULL, this function is called after a precompile header file
 319    is loaded.  */
 320 void (*lang_post_pch_load) (void);
 321
 322 /* Load in the PCH file NAME, open on FD.  It was originally searched for
 323    by ORIG_NAME.  */
 324
 325 void
 326 c_common_read_pch (cpp_reader *pfile, const char *name,
 327                    int fd, const char *orig_name ATTRIBUTE_UNUSED)
 328 {
 329   FILE *f;
 330   struct save_macro_data *smd;
 331   expanded_location saved_loc;
 332   bool saved_trace_includes;
 333
 334   timevar_push (TV_PCH_RESTORE);
 335
 336   f = fdopen (fd, "rb");
 337   if (f == NULL)
 338     {
 339       cpp_errno (pfile, CPP_DL_ERROR, "calling fdopen");
 340       close (fd);
 341       goto end;
 342     }
 343
 344   cpp_get_callbacks (parse_in)->valid_pch = NULL;
 345
 346   /* Save the location and then restore it after reading the PCH.  */
 347   saved_loc = expand_location (line_table->highest_line);
 348   saved_trace_includes = line_table->trace_includes;
 349
 350   timevar_push (TV_PCH_CPP_RESTORE);
 351   cpp_prepare_state (pfile, &smd);
 352   timevar_pop (TV_PCH_CPP_RESTORE);
 353
 354   gt_pch_restore (f);
 355   cpp_set_line_map (pfile, line_table);
 356   rebuild_location_adhoc_htab (line_table);
 357
 358   timevar_push (TV_PCH_CPP_RESTORE);
 359   if (cpp_read_state (pfile, name, f, smd) != 0)
 360     {
 361       fclose (f);
 362       timevar_pop (TV_PCH_CPP_RESTORE);
 363       goto end;
 364     }
 365   timevar_pop (TV_PCH_CPP_RESTORE);
 366
 367
 368   fclose (f);
 369
 370   line_table->trace_includes = saved_trace_includes;
 371   linemap_add (line_table, LC_ENTER, 0, saved_loc.file, saved_loc.line);
 372
 373   /* Give the front end a chance to take action after a PCH file has
 374      been loaded.  */
 375   if (lang_post_pch_load)
 376     (*lang_post_pch_load) ();
 377
 378 end:
 379   timevar_pop (TV_PCH_RESTORE);
 380 }
 381
 382 /* Indicate that no more PCH files should be read.  */
 383
 384 void
 385 c_common_no_more_pch (void)
 386 {
 387   if (cpp_get_callbacks (parse_in)->valid_pch)
 388     {
 389       cpp_get_callbacks (parse_in)->valid_pch = NULL;
 390       host_hooks.gt_pch_use_address (NULL, 0, -1, 0);
 391     }
 392 }
 393
 394 /* Handle #pragma GCC pch_preprocess, to load in the PCH file.  */
 395
 396 void
 397 c_common_pch_pragma (cpp_reader *pfile, const char *name)
 398 {
 399   int fd;
 400
 401   if (!cpp_get_options (pfile)->preprocessed)
 402     {
 403       error ("%<pch_preprocess%> pragma should only be used "
 404              "with %<-fpreprocessed%>");
 405       inform (input_location, "use %<#include%> instead");
 406       return;
 407     }
 408
 409   fd = open (name, O_RDONLY | O_BINARY, 0666);
 410   if (fd == -1)
 411     fatal_error (input_location, "%s: couldn%'t open PCH file: %m", name);
 412
 413   if (c_common_valid_pch (pfile, name, fd) != 1)
 414     {
 415       if (!cpp_get_options (pfile)->warn_invalid_pch)
 416         inform (input_location, "use %<-Winvalid-pch%> for more information");
 417       fatal_error (input_location, "%s: PCH file was invalid", name);
 418     }
 419
 420   c_common_read_pch (pfile, name, fd, name);
 421
 422   close (fd);
 423 }
 424