[PATCH 1/4] New channel `portability-recursive'.

[Ralf Wildenhues]

[ moving from automake@ ]

* Ralf Wildenhues wrote on Sat, Mar 07, 2009 at 04:16:33PM CET:
>   git clone git://git.savannah.gnu.org/automake.git
>   git branch je-silent origin/je-silent

(thanks Jan for the typo fix!)

> Detailed patch descriptions will follow on automake-patches,

This first patch in the series adds a new warning channel for warnings
about recursive variable expansions.

This warning channel is currently turned on by -Wall, but it should also
be turned on by -Wportability, I guess; or get its own switch.  As noted
in some of the earlier discussions, recursive $(var1$(var2)) variable
expansions are in practice found to be rather portable (when the inner
variable uses ${..} or $(..), not plain $..).

As another FIXME note, a warning message would currently output a
slightly bogus string `$(var2', which should be fixed in the
scan_variable_expansions function.  I refrained from that for now,
this is quite a hot code path and I wanted to do some measuring before
adding more non-regular expression matching.

Cheers,
Ralf

    New channel `portability-recursive'.
    
    Add new channel for portability warnings about recursive make
    variable expansions `$(var1$(var2))'.  Enable it alongside
    `-Wportability'.
    
    * lib/Automake/ChannelDefs.pm (Automake::ChannelDefs): Register
    channel `portability-recursive'.
    * lib/Automake/Variable.pm (_VARIABLE_CHARACTERS)
    (_VARIABLE_RECURSIVE_PATTERN): New variables.
    (check_variable_expansions): Diagnose recursive variable
    expansions through the new channel.

diff --git a/lib/Automake/ChannelDefs.pm b/lib/Automake/ChannelDefs.pm
index 15362b5..60520b7 100644
--- a/lib/Automake/ChannelDefs.pm
+++ b/lib/Automake/ChannelDefs.pm
@@ -1,4 +1,4 @@
-# Copyright (C) 2002, 2003, 2006, 2008 Free Software Foundation, Inc.
+# Copyright (C) 2002, 2003, 2006, 2008, 2009 Free Software Foundation, Inc.
 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -154,6 +154,7 @@ register_channel 'gnu', type => 'warning';
 register_channel 'obsolete', type => 'warning', silent => 1;
 register_channel 'override', type => 'warning', silent => 1;
 register_channel 'portability', type => 'warning', silent => 1;
+register_channel 'portability-recursive', type => 'warning', silent => 1;
 register_channel 'syntax', type => 'warning';
 register_channel 'unsupported', type => 'warning';
 
diff --git a/lib/Automake/Variable.pm b/lib/Automake/Variable.pm
index 79bb42c..f826586 100644
--- a/lib/Automake/Variable.pm
+++ b/lib/Automake/Variable.pm
@@ -1,4 +1,4 @@
-# Copyright (C) 2003, 2004, 2005, 2006, 2008  Free Software Foundation, Inc.
+# Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009  Free Software Foundation, 
Inc.
 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -128,7 +128,10 @@ non-object).
 
 =cut
 
-my $_VARIABLE_PATTERN = 'address@hidden' . "\$";
+my $_VARIABLE_CHARACTERS = 'address@hidden';
+my $_VARIABLE_PATTERN = '^' . $_VARIABLE_CHARACTERS . "\$";
+my $_VARIABLE_RECURSIVE_PATTERN =
+    '^(address@hidden|\$[({]' . $_VARIABLE_CHARACTERS . '[})]?)+' . "\$";
 
 # The order in which variables should be output.  (May contain
 # duplicates -- only the first occurrence matters.)
@@ -771,8 +774,17 @@ sub check_variable_expansions ($$)
          # Mention this in the diagnostic.
          my $gnuext = "";
          $gnuext = "\n(probably a GNU make extension)" if $var =~ / /;
-         msg ('portability', $where,
-              "$var: non-POSIX variable name$gnuext");
+         # Accept recursive variable expansions if so desired
+         # (we hope they are rather portable in practice).
+         if ($var =~ /$_VARIABLE_RECURSIVE_PATTERN/o)
+           {
+             msg ('portability-recursive', $where,
+                  "$var: non-POSIX recursive variable expansion$gnuext");
+           }
+         else
+           {
+             msg ('portability', $where, "$var: non-POSIX variable 
name$gnuext");
+           }
        }
     }
 }