2012-03-07  Richard Guenther  <rguenther@suse.de>

	PR pch/52518
	PR pch/38987
	* doc/invoke.texi (Precompiled Headers): Remove sentence that
	suggests you can include PCHs from inside another header.

2009-09-22  Richard Guenther  <rguenther@suse.de>

	PR pch/38987
	* files.c (pch_open_file): Disallow non-toplevel PCH inclusion.

--- libcpp/files.c	(revision 151969)
+++ libcpp/files.c	(revision 151970)
@@ -288,6 +288,12 @@ pch_open_file (cpp_reader *pfile, _cpp_f
   if (file->name[0] == '\0' || !pfile->cb.valid_pch)
     return false;
 
+  /* If the file is not included as first include from either the toplevel
+     file or the command-line it is not a valid use of PCH.  */
+  if (pfile->all_files
+      && pfile->all_files->next_file)
+    return false;
+
   flen = strlen (path);
   len = flen + sizeof (extension);
   pchname = XNEWVEC (char, len);
--- gcc/doc/invoke.texi	(revision 185028)
+++ gcc/doc/invoke.texi	(revision 185029)
@@ -19891,9 +19891,8 @@ Only one precompiled header can be used
 
 @item
 A precompiled header can't be used once the first C token is seen.  You
-can have preprocessor directives before a precompiled header; you can
-even include a precompiled header from inside another header, so long as
-there are no C tokens before the @code{#include}.
+can have preprocessor directives before a precompiled header; you cannot
+include a precompiled header from inside another header.
 
 @item
 The precompiled header file must be produced for the same language as