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libcpp: Stabilize the location for macros restored after PCH load [PR105608]

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libcpp currently lacks the infrastructure to assign correct locations to
macros that were defined prior to loading a PCH and then restored
afterwards. While I plan to address that fully for GCC 15, this patch
improves things by using at least a valid location, even if it's not the
best one. Without this change, libcpp uses pfile->directive_line as the
location for the restored macros, but this location_t applies to the old
line map, not the one that was just restored from the PCH, so the resulting
location is unpredictable and depends on what was stored in the line maps
before. With this change, all restored macros get assigned locations at the
line of the #include that triggered the PCH restore. A future patch will
store the actual file name and line number of each definition and then
synthesize locations in the new line map pointing to the right place.

gcc/c-family/ChangeLog:

	PR preprocessor/105608
	* c-pch.cc (c_common_read_pch): Adjust line map so that libcpp
	assigns a location to restored macros which is the same location
	that triggered the PCH include.

libcpp/ChangeLog:

	PR preprocessor/105608
	* pch.cc (cpp_read_state): Set a valid location for restored
	macros.
This commit is contained in:
Lewis Hyatt 2024-01-31 15:50:11 -05:00
parent 65b105b4f3
commit 019dc63819
2 changed files with 24 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
gcc/c-family/c-pch.cc
View File

@ -318,6 +318,7 @@ c_common_read_pch (cpp_reader *pfile, const char *name,
struct save_macro_data *smd;
expanded_location saved_loc;
bool saved_trace_includes;
int cpp_result;
timevar_push (TV_PCH_RESTORE);
@ -343,20 +344,26 @@ c_common_read_pch (cpp_reader *pfile, const char *name,
cpp_set_line_map (pfile, line_table);
rebuild_location_adhoc_htab (line_table);
line_table->trace_includes = saved_trace_includes;
linemap_add (line_table, LC_ENTER, 0, saved_loc.file, saved_loc.line);
/* Set the current location to the line containing the #include (or the
#pragma GCC pch_preprocess) for the purpose of assigning locations to any
macros that are about to be restored. */
linemap_add (line_table, LC_ENTER, 0, saved_loc.file,
saved_loc.line > 1 ? saved_loc.line - 1 : saved_loc.line);
timevar_push (TV_PCH_CPP_RESTORE);
if (cpp_read_state (pfile, name, f, smd) != 0)
{
fclose (f);
timevar_pop (TV_PCH_CPP_RESTORE);
goto end;
}
cpp_result = cpp_read_state (pfile, name, f, smd);
/* Set the current location to the line following the #include, where we
were prior to processing the PCH. */
linemap_line_start (line_table, saved_loc.line, 0);
timevar_pop (TV_PCH_CPP_RESTORE);
fclose (f);
if (cpp_result != 0)
goto end;
/* Give the front end a chance to take action after a PCH file has
been loaded. */
if (lang_post_pch_load)

9
libcpp/pch.cc
View File

@ -838,7 +838,14 @@ cpp_read_state (cpp_reader *r, const char *name, FILE *f,
!= NULL)
{
_cpp_clean_line (r);
if (!_cpp_create_definition (r, h, 0))
/* ??? Using r->line_table->highest_line is not ideal here, but we
do need to use some location that is relative to the new line
map just loaded, not the old one that was in effect when these
macros were lexed. The proper fix is to remember the file name
and line number where each macro was defined, and then add
these locations into the new line map. See PR105608. */
if (!_cpp_create_definition (r, h, r->line_table->highest_line))
abort ();
_cpp_pop_buffer (r);
}