When we read preprocessed source, we deal with a couple of special
location lines at the start of the file. These provide information
about the original filename of the source and the current directory, so
we can process the source in the same manner. When updating that code,
I had a somewhat philosophical question: Should the line table contain
evidence of the filename the user provided to the compiler? I figured
to leave it there, as it did no harm. But this defect shows an issue.
It's in the line table and our (non optimizing) line table serializer
emits that filename. Which means if one re-preprocesses the original
source to a differently-named intermediate file, the resultant CMI is
different. Boo. That's a difference that doesn't matter, except the
CRC matching then fails. We should elide the filename, so that one can
preprocess to mktemp intermediate filenames for whatever reason.
This patch takes the approach of expunging it from the line table -- so
the line table will end up with exactly the same form. That seems a
better bet than trying to fix up mismatching line tables in CMI emission.
PR c++/99072
libcpp/
* init.c (read_original_filename): Expunge all evidence of the
original filename.
gcc/testsuite/
* g++.dg/modules/pr99072.H: New.
--
Nathan Sidwell
diff --git c/gcc/testsuite/g++.dg/modules/pr99072.H w/gcc/testsuite/g++.dg/modules/pr99072.H
new file mode 100644
index 00000000000..eda0c07f9e2
--- /dev/null
+++ w/gcc/testsuite/g++.dg/modules/pr99072.H
@@ -0,0 +1,10 @@
+# 0 "REALNAME"
+# 0 "<built-in>"
+# 0 "<command-line>"
+# 0 "<command-line>"
+# 1 "/usr/include/stdc-predef.h" 1 3 4
+# 0 "<command-line>" 2
+# 1 "REALNAME"
+
+// { dg-additional-options {-fmodule-header -fpreprocessed -fdump-lang-module-lineno} }
+// { dg-final { scan-lang-dump { 4 source file names\n Source file\[0\]=REALNAME\n Source file\[1\]=<built-in>\n Source file\[2\]=<command-line>\n Source file\[3\]=/usr/include/stdc-predef.h\n} module } }
diff --git c/libcpp/init.c w/libcpp/init.c
index 17b0d251cda..68ed2c761b9 100644
--- c/libcpp/init.c
+++ w/libcpp/init.c
@@ -752,6 +752,23 @@ read_original_filename (cpp_reader *pfile)
if (_cpp_handle_directive (pfile, token->flags & PREV_WHITE))
{
read_original_directory (pfile);
+
+ auto *penult = &linemap_check_ordinary
+ (LINEMAPS_LAST_MAP (pfile->line_table, false))[-1];
+ if (penult[1].reason == LC_RENAME_VERBATIM)
+ {
+ /* Expunge any evidence of the original linemap. */
+ pfile->line_table->highest_location
+ = pfile->line_table->highest_line
+ = penult[0].start_location;
+
+ penult[1].start_location = penult[0].start_location;
+ penult[1].reason = penult[0].reason;
+ penult[0] = penult[1];
+ pfile->line_table->info_ordinary.used--;
+ pfile->line_table->info_ordinary.cache = 0;
+ }
+
return true;
}
}
