patch trunk: seek plugin also in a language specific directory when given a short name

[Basile Starynkevitch <basile at starynkevitch dot net>]

Hello All,

Front-end functions (e.g. pragma-related) are not available to all
plugins (e.g. not to plugins fired from lto1). See the
http://gcc.gnu.org/ml/gcc/2011-05/msg00321.html discussion.

This patch document a little bit that, and search short plugins like 
-fplugin=name in both `gcc -print-file-name=plugin`/name.so  and  
`gcc -print-file-name=plugin`/cc1/name.so or 
`gcc -print-file-name=plugin`/cc1plus/name.so or 
`gcc -print-file-name=plugin`/lto1/name.so .... etc ......
 
############# gcc/ChangeLog entries ################
2011-06-06  Basile Starynkevitch  <basile@starynkevitch.net>

	* doc/plugins.texi (Loading plugins): Plugins are also 
	seeked in a front-end specific subdirectory.
	(Plugin callbacks): lto1 plugins can't register pragma handlers.

	* plugin.c: Update copyright year.
	(PLUGIN_FILE_SUFFIX): New constant macro.
	(add_new_plugin): Search short plugins also in a front-end specific 
	subdirectory.
#####################################################

Attaching patch to trunk 174684

Comments are welcome. Ok for trunk?

Regards.
-- 
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359
8, rue de la Faiencerie, 92340 Bourg La Reine, France
*** opinions {are only mine, sont seulement les miennes} ***

Index: gcc/doc/plugins.texi
===================================================================
--- gcc/doc/plugins.texi	(revision 174684)
+++ gcc/doc/plugins.texi	(working copy)
@@ -23,10 +23,14 @@ plugins as key-value pairs. Multiple plugins can b
 specifying multiple @option{-fplugin} arguments.
 
 A plugin can be simply given by its short name (no dots or
-slashes). When simply passing @option{-fplugin=@var{name}}, the plugin is
-loaded from the @file{plugin} directory, so @option{-fplugin=@var{name}} is
-the same as @option{-fplugin=`gcc -print-file-name=plugin`/@var{name}.so},
-using backquote shell syntax to query the @file{plugin} directory.
+slashes). When simply passing @option{-fplugin=@var{name}}, the plugin
+is loaded from the @file{plugin} directory using if needed a front-end
+specific subdirectory, so @option{-fplugin=@var{name}} is the same as
+@option{-fplugin=`gcc -print-file-name=plugin`/@var{program}/@var{name}.so} or
+@option{-fplugin=`gcc -print-file-name=plugin`/@var{name}.so}, using
+backquote shell syntax to query the @file{plugin} directory, where
+@var{program} is one of @code{cc1}, @code{cc1plus}, @code{lto1} etc. 
+This permits some plugins to be available only to some front-ends.
 
 @section Plugin API
 
@@ -207,10 +211,11 @@ For the PLUGIN_PASS_MANAGER_SETUP, PLUGIN_INFO, PL
 and PLUGIN_REGISTER_GGC_CACHES pseudo-events the @code{callback} should be
 null, and the @code{user_data} is specific.
 
-When the PLUGIN_PRAGMAS event is triggered (with a null
-pointer as data from GCC), plugins may register their own pragmas
-using functions like @code{c_register_pragma} or
-@code{c_register_pragma_with_expansion}.
+When the PLUGIN_PRAGMAS event is triggered (with a null pointer as
+data from GCC), plugins may register their own pragmas using functions
+like @code{c_register_pragma} or
+@code{c_register_pragma_with_expansion}. This is not possible in
+plugins run from @code{lto1}.
 
 @section Interacting with the pass manager
 
Index: gcc/plugin.c
===================================================================
--- gcc/plugin.c	(revision 174684)
+++ gcc/plugin.c	(working copy)
@@ -1,5 +1,5 @@
 /* Support for GCC plugin mechanism.
-   Copyright (C) 2009, 2010 Free Software Foundation, Inc.
+   Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
@@ -117,6 +117,12 @@ get_plugin_base_name (const char *full_name)
 }
 
 
+/* FIXME: the ".so" suffix is currently builtin, since plugins
+   only work on ELF host systems like e.g. Linux or Solaris.  
+   When plugins shall be available on non ELF systems such as
+   Windows or MacOS, this code has to be greatly improved.  */
+#define PLUGIN_FILE_SUFFIX ".so"
+
 /* Create a plugin_name_args object for the given plugin and insert it
    to the hash table. This function is called when
    -fplugin=/path/to/NAME.so or -fplugin=NAME option is processed.  */
@@ -140,17 +146,37 @@ add_new_plugin (const char* plugin_name)
 
   if (name_is_short)
     {
+      char *plugpath;
+      char* foundpath = NULL;
       base_name = CONST_CAST (char*, plugin_name);
-      /* FIXME: the ".so" suffix is currently builtin, since plugins
-	 only work on ELF host systems like e.g. Linux or Solaris.
-	 When plugins shall be available on non ELF systems such as
-	 Windows or MacOS, this code has to be greatly improved.  */
-      plugin_name = concat (default_plugin_dir_name (), "/",
-			    plugin_name, ".so", NULL);
-      if (access (plugin_name, R_OK))
+
+      /* Look for PLUGINDIR/PROGNAME/NAME.so.  This is useful for
+	 front-end specific plugins.  */
+      if (!foundpath)
+	plugpath = concat (default_plugin_dir_name (), "/",
+			   progname, "/",
+			   plugin_name, PLUGIN_FILE_SUFFIX, NULL);
+      if (!access (plugpath, R_OK))
+	foundpath = plugpath;
+      else
+	free (plugpath);
+      
+      /* Look for PLUGINDIR/NAME.so.  This is useful for plugins
+	 common to all front-ends. */
+      if (!foundpath)
+	plugpath = concat (default_plugin_dir_name (), "/",
+			   plugin_name, PLUGIN_FILE_SUFFIX, NULL);
+      if (!access (plugpath, R_OK))
+	foundpath = plugpath;
+      else
+	free (plugpath);
+      
+      if (!foundpath)
 	fatal_error
-	  ("inacessible plugin file %s expanded from short plugin name %s: %m",
-	   plugin_name, base_name);
+	  ("No plugin found under %s for %s from short plugin name %s",
+	   default_plugin_dir_name (), progname, base_name);
+ 
+      plugin_name = foundpath;
     }
   else
     base_name = get_plugin_base_name (plugin_name);