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From: "jruffin at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug pch/56549] #pragma once ineffective with BOM in include file
Date: Mon, 30 Nov 2020 12:51:38 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D56549

--- Comment #7 from Julien Ruffin <jruffin at gmail dot com> ---
Here is the patch for the current master. I have tested it on large C++ code
bases. So far, it builds successfully and significantly faster.

diff --git a/libcpp/files.c b/libcpp/files.c
index 301b2379a23..cbc2b0f4540 100644
--- a/libcpp/files.c
+++ b/libcpp/files.c
@@ -1978,25 +1978,28 @@ _cpp_save_file_entries (cpp_reader *pfile, FILE *fp)
       result->entries[count].once_only =3D f->once_only;
       /* |=3D is avoided in the next line because of an HP C compiler bug =
*/
       result->have_once_only =3D result->have_once_only | f->once_only;
+
       if (f->buffer_valid)
-       md5_buffer ((const char *)f->buffer,
-                   f->st.st_size, result->entries[count].sum);
+        {
+          md5_buffer ((const char *)f->buffer,
+                      f->st.st_size, result->entries[count].sum);
+        }
       else
-       {
-         FILE *ff;
-         int oldfd =3D f->fd;
-
-         if (!open_file (f))
-           {
-             open_file_failed (pfile, f, 0, 0);
-             free (result);
-             return false;
-           }
-         ff =3D fdopen (f->fd, "rb");
-         md5_stream (ff, result->entries[count].sum);
-         fclose (ff);
-         f->fd =3D oldfd;
-       }
+        {
+          if (!read_file (pfile, f, 0))
+            {
+              return false;
+            }
+
+          md5_buffer ((const char *)f->buffer,
+                      f->st.st_size, result->entries[count].sum);
+
+          const void* to_free =3D f->buffer_start;
+          f->buffer_start =3D NULL;
+          f->buffer =3D NULL;
+          f->buffer_valid =3D false;
+          free ((void*) to_free);
+        }
       result->entries[count].size =3D f->st.st_size;
     }=