gcc/c-family/c-pch.c

   1 /* Precompiled header implementation for the C languages.
   2    Copyright (C) 2000-2021 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   uint32_t pch_write_symbols;
  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.pch_write_symbols = 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.pch_write_symbols != write_symbols
 256       && write_symbols != NO_DEBUG)
 257     {
 258       char *created_str = xstrdup (debug_set_names (v.pch_write_symbols));
 259       char *used_str = xstrdup (debug_set_names (write_symbols));
 260       cpp_warning (pfile, CPP_W_INVALID_PCH,
 261                    "%s: created with '%s' debug info, but used with '%s'", name,
 262                    created_str, used_str);
 263       free (created_str);
 264       free (used_str);
 265       return 2;
 266     }
 267
 268   /* Check flags that must match exactly.  */
 269   {
 270     size_t i;
 271     for (i = 0; i < MATCH_SIZE; i++)
 272       if (*pch_matching[i].flag_var != v.match[i])
 273         {
 274           cpp_warning (pfile, CPP_W_INVALID_PCH,
 275                        "%s: settings for %s do not match", name,
 276                        pch_matching[i].flag_name);
 277           return 2;
 278         }
 279   }
 280
 281   /* If the text segment was not loaded at the same address as it was
 282      when the PCH file was created, function pointers loaded from the
 283      PCH will not be valid.  We could in theory remap all the function
 284      pointers, but no support for that exists at present.
 285      Since we have the same executable, it should only be necessary to
 286      check one function.  */
 287   if (v.pch_init != &pch_init)
 288     {
 289       cpp_warning (pfile, CPP_W_INVALID_PCH,
 290                    "%s: had text segment at different address", name);
 291       return 2;
 292     }
 293
 294   /* Check the target-specific validity data.  */
 295   {
 296     void *this_file_data = xmalloc (v.target_data_length);
 297     const char *msg;
 298
 299     if ((size_t) read (fd, this_file_data, v.target_data_length)
 300         != v.target_data_length)
 301       fatal_error (input_location, "cannot read %s: %m", name);
 302     msg = targetm.pch_valid_p (this_file_data, v.target_data_length);
 303     free (this_file_data);
 304     if (msg != NULL)
 305       {
 306         cpp_warning (pfile, CPP_W_INVALID_PCH, "%s: %s", name, msg);
 307         return 2;
 308       }
 309   }
 310
 311   /* Check the preprocessor macros are the same as when the PCH was
 312      generated.  */
 313
 314   result = cpp_valid_state (pfile, name, fd);
 315   if (result == -1)
 316     return 2;
 317   else
 318     return result == 0;
 319 }
 320
 321 /* If non-NULL, this function is called after a precompile header file
 322    is loaded.  */
 323 void (*lang_post_pch_load) (void);
 324
 325 /* Load in the PCH file NAME, open on FD.  It was originally searched for
 326    by ORIG_NAME.  */
 327
 328 void
 329 c_common_read_pch (cpp_reader *pfile, const char *name,
 330                    int fd, const char *orig_name ATTRIBUTE_UNUSED)
 331 {
 332   FILE *f;
 333   struct save_macro_data *smd;
 334   expanded_location saved_loc;
 335   bool saved_trace_includes;
 336
 337   timevar_push (TV_PCH_RESTORE);
 338
 339   f = fdopen (fd, "rb");
 340   if (f == NULL)
 341     {
 342       cpp_errno (pfile, CPP_DL_ERROR, "calling fdopen");
 343       close (fd);
 344       goto end;
 345     }
 346
 347   cpp_get_callbacks (parse_in)->valid_pch = NULL;
 348
 349   /* Save the location and then restore it after reading the PCH.  */
 350   saved_loc = expand_location (line_table->highest_line);
 351   saved_trace_includes = line_table->trace_includes;
 352
 353   timevar_push (TV_PCH_CPP_RESTORE);
 354   cpp_prepare_state (pfile, &smd);
 355   timevar_pop (TV_PCH_CPP_RESTORE);
 356
 357   gt_pch_restore (f);
 358   cpp_set_line_map (pfile, line_table);
 359   rebuild_location_adhoc_htab (line_table);
 360
 361   timevar_push (TV_PCH_CPP_RESTORE);
 362   if (cpp_read_state (pfile, name, f, smd) != 0)
 363     {
 364       fclose (f);
 365       timevar_pop (TV_PCH_CPP_RESTORE);
 366       goto end;
 367     }
 368   timevar_pop (TV_PCH_CPP_RESTORE);
 369
 370
 371   fclose (f);
 372
 373   line_table->trace_includes = saved_trace_includes;
 374   linemap_add (line_table, LC_ENTER, 0, saved_loc.file, saved_loc.line);
 375
 376   /* Give the front end a chance to take action after a PCH file has
 377      been loaded.  */
 378   if (lang_post_pch_load)
 379     (*lang_post_pch_load) ();
 380
 381 end:
 382   timevar_pop (TV_PCH_RESTORE);
 383 }
 384
 385 /* Indicate that no more PCH files should be read.  */
 386
 387 void
 388 c_common_no_more_pch (void)
 389 {
 390   if (cpp_get_callbacks (parse_in)->valid_pch)
 391     {
 392       cpp_get_callbacks (parse_in)->valid_pch = NULL;
 393       host_hooks.gt_pch_use_address (NULL, 0, -1, 0);
 394     }
 395 }
 396
 397 /* Handle #pragma GCC pch_preprocess, to load in the PCH file.  */
 398
 399 void
 400 c_common_pch_pragma (cpp_reader *pfile, const char *name)
 401 {
 402   int fd;
 403
 404   if (!cpp_get_options (pfile)->preprocessed)
 405     {
 406       error ("%<pch_preprocess%> pragma should only be used "
 407              "with %<-fpreprocessed%>");
 408       inform (input_location, "use %<#include%> instead");
 409       return;
 410     }
 411
 412   fd = open (name, O_RDONLY | O_BINARY, 0666);
 413   if (fd == -1)
 414     fatal_error (input_location, "%s: couldn%'t open PCH file: %m", name);
 415
 416   if (c_common_valid_pch (pfile, name, fd) != 1)
 417     {
 418       if (!cpp_get_options (pfile)->warn_invalid_pch)
 419         inform (input_location, "use %<-Winvalid-pch%> for more information");
 420       fatal_error (input_location, "%s: PCH file was invalid", name);
 421     }
 422
 423   c_common_read_pch (pfile, name, fd, name);
 424
 425   close (fd);
 426 }
 427