[committed] --enable-stage1-languages and show "supported" rather than "recognized" languages

[Paolo Bonzini <paolo dot bonzini at lu dot unisi dot ch>]

This patch is a revamped version of an older, never committed patch to 
add a --enable-stage1-languages option to toplevel configure.  In 
addition to that, this patch:

1) simplifies the logic with which we choose languages to build.  The 
current usage of complicated case-statement patterns is hard to 
maintain.  This patch improves the situation.

2) prints "supported" languages (considering languages disabled by the 
current target), instead of "recognized" languages.

Bootstrapped/regtested i686-pc-linux-gnu (plus tested various other 
combinations of options).

Paolo
2006-12-29  Paolo Bonzini  <bonzini@gnu.org>

	* configure.in: Reorganize recognition of languages.  Add
	--enable-stage1-languages.  Show supported languages for the chosen
	target rather than all recognized languages.
	* configure: Regenerate.

Index: configure.in
===================================================================
--- configure.in	(revision 120269)
+++ configure.in	(working copy)
@@ -1153,8 +1153,7 @@ AC_SUBST(gmplibs)
 AC_SUBST(gmpinc)
 
 # By default, C is the only stage 1 language.
-stage1_languages=c
-AC_SUBST(stage1_languages)
+stage1_languages=,c,
 
 # Figure out what language subdirectories are present.
 # Look if the user specified --enable-languages="..."; if not, use
@@ -1216,9 +1215,9 @@ if test -d ${srcdir}/gcc; then
     esac
   done
 
-  new_enable_languages=c
+  new_enable_languages=,c,
   missing_languages=`echo ",$enable_languages," | sed -e s/,all,/,/ -e s/,c,/,/ `
-  potential_languages=c
+  potential_languages=,c,
 
   for lang_frag in ${srcdir}/gcc/*/config-lang.in .. ; do
     case ${lang_frag} in
@@ -1233,32 +1232,22 @@ if test -d ${srcdir}/gcc; then
         target_libs=
         lang_dirs=
         subdir_requires=
-        boot_language=
-        build_by_default=
+        boot_language=no
+        build_by_default=yes
         . ${lang_frag}
-        potential_languages="${potential_languages},${language}"
-        # This is quite sensitive to the ordering of the case statement arms.
-        case ,${enable_languages},:${language}:${have_gnat}:${build_by_default} in
-          *::*:*)
-            echo "${lang_frag} doesn't set \$language." 1>&2
-            exit 1
-            ;;
-          *:ada:no:*)
-            # Ada was requested with no preexisting GNAT.  Disable unconditionally.
-            add_this_lang=no
-            ;;
-          *,${language},*:*:*:*)
+        if test x${language} = x; then
+          echo "${lang_frag} doesn't set \$language." 1>&2
+          exit 1
+        fi
+
+        case ,${enable_languages}, in
+          *,${language},*)
             # Language was explicitly selected; include it.
             add_this_lang=yes
             ;;
-          *,all,*:*:*:no)
-            # 'all' was selected, but this is not a default language
-            # so do not include it.
-            add_this_lang=no
-            ;;
-          *,all,*:*:*:*)
-            # 'all' was selected and this is a default language; include it.
-            add_this_lang=yes
+          *,all,*)
+            # 'all' was selected, select it if it is a default language
+            add_this_lang=${build_by_default}
             ;;
           *)
             add_this_lang=no
@@ -1275,30 +1264,48 @@ if test -d ${srcdir}/gcc; then
               ;;
             *)
               # Silently disable.
-              add_this_lang=no
+              add_this_lang=unsupported
               ;;
           esac
 	done
 
+        # Disable Ada if no preexisting GNAT is available.
+        case ,${enable_languages},:${language}:${have_gnat} in
+          *,${language},*:ada:no)
+            # Specifically requested language; tell them.
+            AC_MSG_ERROR([GNAT is required to build $language])
+            ;;
+          *:ada:no)
+            # Silently disable.
+            add_this_lang=unsupported
+            ;;
+        esac
+
 	# Disable a language that is unsupported by the target.
 	case " $unsupported_languages " in
 	  *" $language "*)
-	    add_this_lang=no
+	    add_this_lang=unsupported
 	    ;;
 	esac
 
 	case $add_this_lang in
-	  no)
+	  unsupported)
             # Remove language-dependent dirs.
             eval noconfigdirs='"$noconfigdirs "'\"$target_libs $lang_dirs\"
 	    ;;
-          *)
-	    new_enable_languages="$new_enable_languages,$language"
+	  no)
+            # Remove language-dependent dirs; still show language as supported.
+            eval noconfigdirs='"$noconfigdirs "'\"$target_libs $lang_dirs\"
+            potential_languages="${potential_languages}${language},"
+	    ;;
+          yes)
+	    new_enable_languages="${new_enable_languages}${language},"
+            potential_languages="${potential_languages}${language},"
 	    missing_languages=`echo "$missing_languages" | sed "s/,$language,/,/"`
 	    case ${boot_language} in
 	      yes)
 		# Add to (comma-separated) list of stage 1 languages.
-		stage1_languages="${stage1_languages},${language}"
+		stage1_languages="${stage1_languages}${language},"
 		;;
 	    esac
 	    ;;
@@ -1307,17 +1314,55 @@ if test -d ${srcdir}/gcc; then
     esac
   done
 
+  AC_ARG_ENABLE(stage1-languages,
+[  --enable-stage1-languages[=all]   choose additional languages to build during
+                          stage1.  Mostly useful for compiler development.],
+  [case ,${enable_stage1_languages}, in
+    ,no,|,,)
+      # Set it to something that will have no effect in the loop below
+      enable_stage1_languages=c ;;
+    ,yes,)
+      enable_stage1_languages=`echo $new_enable_languages | \
+	sed -e "s/^,//" -e "s/,$//" ` ;;
+    *,all,*)
+      enable_stage1_languages=`echo ,$enable_stage1_languages, | \
+	sed -e "s/,all,/$new_enable_languages/" -e "s/^,//" -e "s/,$//" ` ;;
+  esac
+
+  # Add "good" languages from enable_stage1_languages to stage1_languages,
+  # while "bad" languages go in missing_languages.  Leave no duplicates.
+  for i in `echo $enable_stage1_languages | sed 's/,/ /g' `; do
+    case $potential_languages in
+      *,$i,*)
+        case $stage1_languages in
+          *,$i,*) ;;
+          *) stage1_languages="$stage1_languages$i," ;;
+        esac ;;
+      *)
+        case $missing_languages in
+          *,$i,*) ;;
+          *) missing_languages="$missing_languages$i," ;;
+        esac ;;
+     esac
+  done])
+
+  # Remove leading/trailing commas that were added for simplicity
+  potential_languages=`echo "$potential_languages" | sed -e "s/^,//" -e "s/,$//"`
   missing_languages=`echo "$missing_languages" | sed -e "s/^,//" -e "s/,$//"`
+  stage1_languages=`echo "$stage1_languages" | sed -e "s/^,//" -e "s/,$//"`
+  new_enable_languages=`echo "$new_enable_languages" | sed -e "s/^,//" -e "s/,$//"`
+
   if test "x$missing_languages" != x; then
     AC_MSG_ERROR([
 The following requested languages could not be built: ${missing_languages}
-Recognised languages are: ${potential_languages}])
+Supported languages are: ${potential_languages}])
   fi
-
   if test "x$new_enable_languages" != "x$enable_languages"; then
     echo The following languages will be built: ${new_enable_languages}
+    enable_languages="$new_enable_languages"
   fi
-  enable_languages="$new_enable_languages"
+
+  AC_SUBST(stage1_languages)
   ac_configure_args=`echo " $ac_configure_args" | sed -e 's/ --enable-languages=[[^ ]]*//' -e 's/$/ --enable-languages='"$enable_languages"/ `
 fi