cppinit.c (remove_dup_dir): Add head_ptr argument to handle removal at head.

	* cppinit.c (remove_dup_dir): Add head_ptr argument to handle removal
	at head.
	(remove_dup_nonsys_dirs): New function.
	(remove_dup_dirs): Change argument head to head_ptr.  Remove warnings.
	(merge_include_chains): Remove non-system include directories from
	quote and bracket include chains when they duplicate equivalent system
	directories.
	* doc/cpp.texi (-I): Update.
        * doc/cppopts.texi (-I): Update.
        * doc/install.texi (--with-local-prefix): Further document usage of
	this option.
	* doc/invoke.texi (-I): Update.

From-SVN: r56468

6 files changed, 160 insertions, 63 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5a70ba7..8df1641 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,18 @@
+2002-08-20  John David Anglin  <dave@hiauly1.hia.nrc.ca>
+
+	* cppinit.c (remove_dup_dir): Add head_ptr argument to handle removal
+	at head.
+	(remove_dup_nonsys_dirs): New function.
+	(remove_dup_dirs): Change argument head to head_ptr.  Remove warnings.
+	(merge_include_chains): Remove non-system include directories from
+	quote and bracket include chains when they duplicate equivalent system
+	directories.
+	* doc/cpp.texi (-I): Update.
+        * doc/cppopts.texi (-I): Update.
+        * doc/install.texi (--with-local-prefix): Further document usage of
+	this option.
+	* doc/invoke.texi (-I): Update.
+
 2002-08-20  Richard Henderson  <rth@redhat.com>
 
 	* expr.c (TARGET_MEM_FUNCTIONS): Transform to boolean.
diff --git a/gcc/cppinit.c b/gcc/cppinit.c
index 0c61086..bdee5a6 100644
--- a/gcc/cppinit.c
+++ b/gcc/cppinit.c
@@ -94,9 +94,13 @@ static void mark_named_operators	PARAMS ((cpp_reader *));
 static void append_include_chain	PARAMS ((cpp_reader *,
 						 char *, int, int));
 static struct search_path * remove_dup_dir	PARAMS ((cpp_reader *,
+						 struct search_path *,
+						 struct search_path **));
+static struct search_path * remove_dup_nonsys_dirs PARAMS ((cpp_reader *,
+						 struct search_path **,
 						 struct search_path *));
 static struct search_path * remove_dup_dirs PARAMS ((cpp_reader *,
-						 struct search_path *));
+						 struct search_path **));
 static void merge_include_chains	PARAMS ((cpp_reader *));
 static bool push_include		PARAMS ((cpp_reader *,
 						 struct pending_option *));
@@ -257,55 +261,92 @@ append_include_chain (pfile, dir, path, cxx_aware)
 }
 
 /* Handle a duplicated include path.  PREV is the link in the chain
-   before the duplicate.  The duplicate is removed from the chain and
-   freed.  Returns PREV.  */
+   before the duplicate, or NULL if the duplicate is at the head of
+   the chain.  The duplicate is removed from the chain and freed.
+   Returns PREV.  */
 static struct search_path *
-remove_dup_dir (pfile, prev)
+remove_dup_dir (pfile, prev, head_ptr)
      cpp_reader *pfile;
      struct search_path *prev;
+     struct search_path **head_ptr;
 {
-  struct search_path *cur = prev->next;
+  struct search_path *cur;
+
+  if (prev != NULL)
+    {
+      cur = prev->next;
+      prev->next = cur->next;
+    }
+  else
+    {
+      cur = *head_ptr;
+      *head_ptr = cur->next;
+    }
 
   if (CPP_OPTION (pfile, verbose))
     fprintf (stderr, _("ignoring duplicate directory \"%s\"\n"), cur->name);
 
-  prev->next = cur->next;
   free ((PTR) cur->name);
   free (cur);
 
   return prev;
 }
 
+/* Remove duplicate non-system directories for which there is an equivalent
+   system directory latter in the chain.  The range for removal is between
+   *HEAD_PTR and END.  Returns the directory before END, or NULL if none.
+   This algorithm is quadratic in the number system directories, which is
+   acceptable since there aren't usually that many of them.  */
+static struct search_path *
+remove_dup_nonsys_dirs (pfile, head_ptr, end)
+     cpp_reader *pfile;
+     struct search_path **head_ptr;
+     struct search_path *end;
+{
+  struct search_path *prev, *cur, *other;
+
+  for (cur = *head_ptr; cur; cur = cur->next)
+    {
+      if (cur->sysp)
+	{
+	  for (other = *head_ptr, prev = NULL;
+	       other != end;
+	       other = other ? other->next : *head_ptr)
+	    {
+	      if (!other->sysp
+		  && INO_T_EQ (cur->ino, other->ino)
+		  && cur->dev == other->dev)
+		{
+		  other = remove_dup_dir (pfile, prev, head_ptr);
+		  if (CPP_OPTION (pfile, verbose))
+		    fprintf (stderr,
+  _("  as it is a non-system directory that duplicates a system directory\n"));
+		}
+	      prev = other;
+	    }
+	}
+    }
+
+  return prev;
+}
+
 /* Remove duplicate directories from a chain.  Returns the tail of the
    chain, or NULL if the chain is empty.  This algorithm is quadratic
    in the number of -I switches, which is acceptable since there
    aren't usually that many of them.  */
 static struct search_path *
-remove_dup_dirs (pfile, head)
+remove_dup_dirs (pfile, head_ptr)
      cpp_reader *pfile;
-     struct search_path *head;
+     struct search_path **head_ptr;
 {
   struct search_path *prev = NULL, *cur, *other;
 
-  for (cur = head; cur; cur = cur->next)
+  for (cur = *head_ptr; cur; cur = cur->next)
     {
-      for (other = head; other != cur; other = other->next)
+      for (other = *head_ptr; other != cur; other = other->next)
 	if (INO_T_EQ (cur->ino, other->ino) && cur->dev == other->dev)
 	  {
-	    if (cur->sysp && !other->sysp)
-	      {
-		cpp_error (pfile, DL_WARNING,
-			   "changing search order for system directory \"%s\"",
-			   cur->name);
-		if (strcmp (cur->name, other->name))
-		  cpp_error (pfile, DL_WARNING,
-			     "  as it is the same as non-system directory \"%s\"",
-			     other->name);
-		else
-		  cpp_error (pfile, DL_WARNING,
-			     "  as it has already been specified as a non-system directory");
-	      }
-	    cur = remove_dup_dir (pfile, prev);
+	    cur = remove_dup_dir (pfile, prev, head_ptr);
 	    break;
 	  }
       prev = cur;
@@ -343,28 +384,33 @@ merge_include_chains (pfile)
   else
     brack = systm;
 
-  /* This is a bit tricky.  First we drop dupes from the quote-include
-     list.  Then we drop dupes from the bracket-include list.
-     Finally, if qtail and brack are the same directory, we cut out
-     brack and move brack up to point to qtail.
+  /* This is a bit tricky.  First we drop non-system dupes of system
+     directories from the merged bracket-include list.  Next we drop
+     dupes from the bracket and quote include lists.  Then we drop
+     non-system dupes from the merged quote-include list.  Finally,
+     if qtail and brack are the same directory, we cut out brack and
+     move brack up to point to qtail.
 
      We can't just merge the lists and then uniquify them because
      then we may lose directories from the <> search path that should
-     be there; consider -Ifoo -Ibar -I- -Ifoo -Iquux. It is however
+     be there; consider -Ifoo -Ibar -I- -Ifoo -Iquux.  It is however
      safe to treat -Ibar -Ifoo -I- -Ifoo -Iquux as if written
      -Ibar -I- -Ifoo -Iquux.  */
 
-  remove_dup_dirs (pfile, brack);
-  qtail = remove_dup_dirs (pfile, quote);
+  remove_dup_nonsys_dirs (pfile, &brack, systm);
+  remove_dup_dirs (pfile, &brack);
 
   if (quote)
     {
+      qtail = remove_dup_dirs (pfile, &quote);
       qtail->next = brack;
 
+      qtail = remove_dup_nonsys_dirs (pfile, &quote, brack);
+
       /* If brack == qtail, remove brack as it's simpler.  */
-      if (brack && INO_T_EQ (qtail->ino, brack->ino)
+      if (qtail && brack && INO_T_EQ (qtail->ino, brack->ino)
 	  && qtail->dev == brack->dev)
-	brack = remove_dup_dir (pfile, qtail);
+	brack = remove_dup_dir (pfile, qtail, &quote);
     }
   else
     quote = brack;
diff --git a/gcc/doc/cpp.texi b/gcc/doc/cpp.texi
index 1284a39..71f0d87 100644
--- a/gcc/doc/cpp.texi
+++ b/gcc/doc/cpp.texi
@@ -823,11 +823,22 @@ version of GCC in use.
 
 You can add to this list with the @option{-I@var{dir}} command line
 option.  All the directories named by @option{-I} are searched, in
-left-to-right order, @emph{before} the default directories.  You can
-also prevent GCC from searching any of the default directories with the
-@option{-nostdinc} option.  This is useful when you are compiling an
+left-to-right order, @emph{before} the default directories.  The only
+exception is when @file{dir} is already searched by default.  In
+this case, the option is ignored and the search order for system
+directories remains unchanged.
+
+Duplicate directories are removed from the quote and bracket search
+chains before the two chains are merged to make the final search chain.
+Thus, it is possible for a directory to occur twice in the final search
+chain if it was specified in both the quote and bracket chains.
+
+You can prevent GCC from searching any of the default directories with
+the @option{-nostdinc} option.  This is useful when you are compiling an
 operating system kernel or some other program that does not use the
 standard C library facilities, or the standard C library itself.
+@option{-I} options are not ignored as described above when
+@option{-nostdinc} is in effect.
 
 GCC looks for headers requested with @code{@w{#include "@var{file}"}}
 first in the directory containing the current file, then in the same
@@ -836,12 +847,6 @@ For example, if @file{/usr/include/sys/stat.h} contains
 @code{@w{#include "types.h"}}, GCC looks for @file{types.h} first in
 @file{/usr/include/sys}, then in its usual search path.
 
-If you name a search directory with @option{-I@var{dir}} that is also a
-system include directory, the @option{-I} wins; the directory will be
-searched according to the @option{-I} ordering, and it will not be
-treated as a system include directory. GCC will warn you when a system
-include directory is hidden in this way.
-
 @samp{#line} (@pxref{Line Control}) does not change GCC's idea of the
 directory containing the current file.
 
@@ -1074,8 +1079,8 @@ found in that directory will be considered system headers.
 All directories named by @option{-isystem} are searched @emph{after} all
 directories named by @option{-I}, no matter what their order was on the
 command line.  If the same directory is named by both @option{-I} and
-@option{-isystem}, @option{-I} wins; it is as if the @option{-isystem} option
-had never been specified at all. GCC warns you when this happens.
+@option{-isystem}, the @option{-I} option is ignored.  GCC provides an
+informative message when this occurs if @option{-v} is used.
 
 @findex #pragma GCC system_header
 There is also a directive, @code{@w{#pragma GCC system_header}}, which
@@ -1817,9 +1822,7 @@ conformance to the C Standard.  CPP follows the host convention when
 processing system header files, but when processing user files
 @code{__STDC__} is always 1.  This has been reported to cause problems;
 for instance, some versions of Solaris provide X Windows headers that
-expect @code{__STDC__} to be either undefined or 1.  You may be able to
-work around this sort of problem by using an @option{-I} option to
-cancel treatment of those headers as system headers.  @xref{Invocation}.
+expect @code{__STDC__} to be either undefined or 1.  @xref{Invocation}.
 
 @item __STDC_VERSION__
 This macro expands to the C Standard's version number, a long integer
diff --git a/gcc/doc/cppopts.texi b/gcc/doc/cppopts.texi
index b23c9fc..e2265eb 100644
--- a/gcc/doc/cppopts.texi
+++ b/gcc/doc/cppopts.texi
@@ -51,16 +51,14 @@ for header files.
 @xref{Search Path}.
 @end ifset
 Directories named by @option{-I} are searched before the standard
-system include directories.
-
-It is dangerous to specify a standard system include directory in an
-@option{-I} option.  This defeats the special treatment of system
-headers
+system include directories.  If the directory @var{dir} is a standard
+system include directory, the option is ignored to ensure that the
+default search order for system directories and the special treatment
+of system headers are not defeated
 @ifset cppmanual
 (@pxref{System Headers})
 @end ifset
-.  It can also defeat the repairs to buggy system headers which GCC
-makes when it is installed.
+.
 
 @item -o @var{file}
 @opindex o
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index d8c92a4..9e2d629 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -467,6 +467,43 @@ any in that directory---are not part of GCC@.  They are part of other
 programs---perhaps many others.  (GCC installs its own header files in
 another directory which is based on the @option{--prefix} value.)
 
+Both the local-prefix include directory and the GCC-prefix include
+directory are part of GCC's "system include" directories.  Although these
+two directories are not fixed, they need to be searched in the proper
+order for the correct processing of the include_next directive.  The
+local-prefix include directory is searched before the GCC-prefix
+include directory.  Another characteristic of system include directories
+is that pedantic warnings are turned off for headers in these directories.
+
+Some autoconf macros add @option{-I @var{directory}} options to the
+compiler command line, to ensure that directories containing installed
+packages' headers are searched.  When @var{directory} is one of GCC's
+system include directories, GCC will ignore the option so that system
+directories continue to be processed in the correct order.  This
+may result in a search order different from what was specified but the
+directory will still be searched.
+
+GCC automatically searches for ordinary libraries using
+@env{GCC_EXEC_PREFIX}.  Thus, when the same installation prefix is
+used for both GCC and packages, GCC will automatically search for
+both headers and libraries.  This provides a configuration that is
+easy to use.  GCC behaves in a manner similar to that when it is
+installed as a system compiler in @file{/usr}.
+
+Sites that need to install multiple versions of GCC may not want to
+use the above simple configuration.  It is possible to use the
+@option{--program-prefix}, @option{--program-suffix} and
+@option{--program-transform-name} options to install multiple versions
+into a single directory, but it may be simpler to use different prefixes
+and the @option{--with-local-prefix} option to specify the location of the
+site-specific files for each version.  It will then be necessary for
+users to specify explicitly the location of local site libraries
+(e.g., with @env{LIBRARY_PATH}).
+
+The same value can be used for both @option{--with-local-prefix} and
+@option{--prefix} provided it is not @file{/usr}.  This can be used
+to avoid the default search of @file{/usr/local/include}.
+
 @strong{Do not} specify @file{/usr} as the @option{--with-local-prefix}!
 The directory you use for @option{--with-local-prefix} @strong{must not}
 contain any of the system's standard header files.  If it did contain
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3119c45..d2fc0f7 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -4281,15 +4281,13 @@ one @option{-I} option, the directories are scanned in left-to-right
 order; the standard system directories come after.
 
 If a standard system include directory, or a directory specified with
-@option{-isystem}, is also specified with @option{-I}, it will be
-searched only in the position requested by @option{-I}.  Also, it will
-not be considered a system include directory.  If that directory really
-does contain system headers, there is a good chance that they will
-break.  For instance, if GCC's installation procedure edited the headers
-in @file{/usr/include} to fix bugs, @samp{-I/usr/include} will cause the
-original, buggy headers to be found instead of the corrected ones.  GCC
-will issue a warning when a system include directory is hidden in this
-way.
+@option{-isystem}, is also specified with @option{-I}, the @option{-I}
+option will be ignored.  The directory will still be searched but as a
+system directory at its normal position in the system include chain.
+This is to ensure that GCC's procedure to fix buggy system headers and
+the ordering for the include_next directive are not inadvertantly changed.
+If you really need to change the search order for system directories,
+use the @option{-nostdinc} and/or @option{-isystem} options.
 
 @item -I-
 @opindex I-