1/* Precompiled header implementation for the C languages.
2 Copyright (C) 2000-2025 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify
7it under the terms of the GNU General Public License as published by
8the Free Software Foundation; either version 3, or (at your option)
9any later version.
10
11GCC is distributed in the hope that it will be useful,
12but WITHOUT ANY WARRANTY; without even the implied warranty of
13MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14GNU General Public License for more details.
15
16You should have received a copy of the GNU General Public License
17along 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#include "diagnostic.h"
32
33/* This is a list of flag variables that must match exactly, and their
34 names for the error message. The possible values for *flag_var must
35 fit in a 'signed char'. */
36
37static const struct c_pch_matching
38{
39 int *flag_var;
40 const char *flag_name;
41} pch_matching[] = {
42 { .flag_var: &flag_exceptions, .flag_name: "-fexceptions" },
43};
44
45enum {
46 MATCH_SIZE = ARRAY_SIZE (pch_matching)
47};
48
49/* Information about flags and suchlike that affect PCH validity.
50
51 Before this structure is read, both an initial 8-character identification
52 string, and a 16-byte checksum, have been read and validated. */
53
54struct c_pch_validity
55{
56 uint32_t pch_write_symbols;
57 signed char match[MATCH_SIZE];
58 size_t target_data_length;
59};
60
61#define IDENT_LENGTH 8
62
63/* The file we'll be writing the PCH to. */
64static FILE *pch_outfile;
65
66static 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
73static const char *
74get_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 (dest: result, src: 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
88static 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
93void
94pch_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 (filename: pch_file, modes: "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 (s: &v, c: '\0', n: 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 target_validity = targetm.get_pch_validity (&v.target_data_length);
121
122 if (fwrite (ptr: partial_pch, IDENT_LENGTH, n: 1, s: f) != 1
123 || fwrite (ptr: executable_checksum, size: 16, n: 1, s: f) != 1
124 || fwrite (ptr: &v, size: sizeof (v), n: 1, s: f) != 1
125 || fwrite (ptr: target_validity, size: v.target_data_length, n: 1, s: f) != 1)
126 fatal_error (input_location, "cannot write to %s: %m", pch_file);
127
128 /* Let the debugging format deal with the PCHness. */
129 (*debug_hooks->handle_pch) (0);
130
131 if (pch_ready_to_save_cpp_state)
132 pch_cpp_save_state ();
133
134 XDELETE (target_validity);
135}
136
137/* Whether preprocessor state has been saved in a PCH file. */
138
139static bool pch_cpp_state_saved = false;
140
141/* Save preprocessor state in a PCH file, after implicitly included
142 headers have been read. If the PCH file has not yet been opened,
143 record that state should be saved when it is opened. */
144
145void
146pch_cpp_save_state (void)
147{
148 if (!pch_cpp_state_saved)
149 {
150 if (pch_outfile)
151 {
152 cpp_save_state (parse_in, pch_outfile);
153 pch_cpp_state_saved = true;
154 }
155 else
156 pch_ready_to_save_cpp_state = true;
157 }
158}
159
160/* Write the PCH file. This is called at the end of a compilation which
161 will produce a PCH file. */
162
163void
164c_common_write_pch (void)
165{
166 timevar_push (tv: TV_PCH_SAVE);
167
168 targetm.prepare_pch_save ();
169
170 (*debug_hooks->handle_pch) (1);
171
172 prepare_target_option_nodes_for_pch ();
173
174 cpp_write_pch_deps (parse_in, pch_outfile);
175
176 gt_pch_save (f: pch_outfile);
177
178 timevar_push (tv: TV_PCH_CPP_SAVE);
179 cpp_write_pch_state (parse_in, pch_outfile);
180 timevar_pop (tv: TV_PCH_CPP_SAVE);
181
182 if (global_dc->pch_save (f: pch_outfile) < 0
183 || fseek (stream: pch_outfile, off: 0, SEEK_SET) != 0
184 || fwrite (ptr: get_ident (), IDENT_LENGTH, n: 1, s: pch_outfile) != 1)
185 fatal_error (input_location, "cannot write %s: %m", pch_file);
186
187 fclose (stream: pch_outfile);
188
189 timevar_pop (tv: 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
197int
198c_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: fd, buf: 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, msgid: "%s: too short to be a PCH file",
219 name);
220 return 2;
221 }
222
223 pch_ident = get_ident();
224 if (memcmp (s1: ident, s2: pch_ident, IDENT_LENGTH) != 0)
225 {
226 if (memcmp (s1: ident, s2: pch_ident, n: 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 msgid: "%s: not compatible with this GCC version", name);
230 else if (memcmp (s1: ident, s2: pch_ident, n: 4) == 0)
231 /* It's a PCH for the wrong language. */
232 cpp_warning (pfile, CPP_W_INVALID_PCH, msgid: "%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, msgid: "%s: not a PCH file", name);
237 return 2;
238 }
239 if (memcmp (s1: ident + IDENT_LENGTH, s2: executable_checksum, n: 16) != 0)
240 {
241 cpp_warning (pfile, CPP_W_INVALID_PCH,
242 msgid: "%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: fd, buf: &v, nbytes: 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 (w_symbols: v.pch_write_symbols));
259 char *used_str = xstrdup (debug_set_names (write_symbols));
260 cpp_warning (pfile, CPP_W_INVALID_PCH,
261 msgid: "%s: created with '%s' debug info, but used with '%s'", name,
262 created_str, used_str);
263 free (ptr: created_str);
264 free (ptr: 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 msgid: "%s: settings for %s do not match", name,
276 pch_matching[i].flag_name);
277 return 2;
278 }
279 }
280
281 /* Check the target-specific validity data. */
282 {
283 void *this_file_data = xmalloc (v.target_data_length);
284 const char *msg;
285
286 if ((size_t) read (fd: fd, buf: this_file_data, nbytes: v.target_data_length)
287 != v.target_data_length)
288 fatal_error (input_location, "cannot read %s: %m", name);
289 msg = targetm.pch_valid_p (this_file_data, v.target_data_length);
290 free (ptr: this_file_data);
291 if (msg != NULL)
292 {
293 cpp_warning (pfile, CPP_W_INVALID_PCH, msgid: "%s: %s", name, msg);
294 return 2;
295 }
296 }
297
298 /* Check the preprocessor macros are the same as when the PCH was
299 generated. */
300
301 result = cpp_valid_state (pfile, name, fd);
302 if (result == -1)
303 return 2;
304 else
305 return result == 0;
306}
307
308/* If non-NULL, this function is called after a precompile header file
309 is loaded. */
310void (*lang_post_pch_load) (void);
311
312/* Load in the PCH file NAME, open on FD. It was originally searched for
313 by ORIG_NAME. */
314
315void
316c_common_read_pch (cpp_reader *pfile, const char *name,
317 int fd, const char *orig_name ATTRIBUTE_UNUSED)
318{
319 FILE *f;
320 struct save_macro_data *smd;
321 expanded_location saved_loc;
322 bool saved_trace_includes;
323 int cpp_result;
324
325 timevar_push (tv: TV_PCH_RESTORE);
326
327 f = fdopen (fd, "rb");
328 if (f == NULL)
329 {
330 cpp_errno (pfile, CPP_DL_ERROR, msgid: "calling fdopen");
331 close (fd: fd);
332 goto end;
333 }
334
335 cpp_get_callbacks (parse_in)->valid_pch = NULL;
336
337 /* Save the location and then restore it after reading the PCH. */
338 saved_loc = expand_location (line_table->highest_line);
339 saved_trace_includes = line_table->trace_includes;
340
341 timevar_push (tv: TV_PCH_CPP_RESTORE);
342 cpp_prepare_state (pfile, &smd);
343 timevar_pop (tv: TV_PCH_CPP_RESTORE);
344
345 gt_pch_restore (f);
346 cpp_set_line_map (pfile, line_table);
347 rebuild_location_adhoc_htab (line_table);
348 line_table->trace_includes = saved_trace_includes;
349
350 /* Set the current location to the line containing the #include (or the
351 #pragma GCC pch_preprocess) for the purpose of assigning locations to any
352 macros that are about to be restored. */
353 linemap_add (line_table, LC_ENTER, sysp: 0, to_file: saved_loc.file,
354 to_line: saved_loc.line > 1 ? saved_loc.line - 1 : saved_loc.line);
355
356 timevar_push (tv: TV_PCH_CPP_RESTORE);
357 cpp_result = cpp_read_state (pfile, name, f, smd);
358
359 /* Set the current location to the line following the #include, where we
360 were prior to processing the PCH. */
361 linemap_line_start (set: line_table, to_line: saved_loc.line, max_column_hint: 0);
362
363 timevar_pop (tv: TV_PCH_CPP_RESTORE);
364
365 if (global_dc->pch_restore (f) < 0)
366 fatal_error (input_location, "cannot read %s: %m", name);
367
368 fclose (stream: f);
369
370 if (cpp_result != 0)
371 goto end;
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
378end:
379 timevar_pop (tv: TV_PCH_RESTORE);
380}
381
382/* Indicate that no more PCH files should be read. */
383
384void
385c_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 void *addr = NULL;
391 host_hooks.gt_pch_use_address (addr, 0, -1, 0);
392 }
393}
394
395/* Handle #pragma GCC pch_preprocess, to load in the PCH file. */
396
397void
398c_common_pch_pragma (cpp_reader *pfile, const char *name)
399{
400 int fd;
401
402 if (!cpp_get_options (pfile)->preprocessed)
403 {
404 error ("%<pch_preprocess%> pragma should only be used "
405 "with %<-fpreprocessed%>");
406 inform (input_location, "use %<#include%> instead");
407 return;
408 }
409
410 fd = open (file: name, O_RDONLY | O_BINARY, 0666);
411 if (fd == -1)
412 fatal_error (input_location, "%s: couldn%'t open PCH file: %m", name);
413
414 if (c_common_valid_pch (pfile, name, fd) != 1)
415 {
416 if (!cpp_get_options (pfile)->warn_invalid_pch)
417 inform (input_location, "use %<-Winvalid-pch%> for more information");
418 fatal_error (input_location, "%s: PCH file was invalid", name);
419 }
420
421 c_common_read_pch (pfile, name, fd, orig_name: name);
422
423 close (fd: fd);
424}
425
426

source code of gcc/c-family/c-pch.cc