[RFA] Fix "set lang auto" oddity when inferior not started yet

[Joel Brobecker <brobecker@adacore.com>]

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Consider the following scenario:

        (gdb) file my_c_program
        (gdb) show lang
        The current source language is "auto; currently c".
        (gdb) set lang ada

Now, try to set the language_mode back to "auto", and see what
the language is:

        (gdb) set lang auto 
        (gdb) show lang
        The current source language is "auto".

We forgot to set the language!  This was reported to us a while ago
by the GPS team (GPS is an IDE that contains a frontend to GDB),
because they rely in some occasions on GDB to tell them what the
language is.

The attached patch fixes the problem.

2008-01-02  Joel Brobecker  <brobecker@adacore.com>

        * symfile.c (set_initial_language): Make non-static.
        * symfile.h (set_initial_language): Add declaration.
        * language.c: #include "symfile.h".
        (set_language): Call set_initial_language if the frame language
        could not be determined.

I also wrote a tiny testcase:

2008-01-02  Joel Brobecker  <brobecker@adacore.com>

        * gdb.base/set_lang_auto.exp: New testcase.

All tested on x86-linux, no regression.
OK to commit?

Thanks,
-- 
Joel

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Index: symfile.c
===================================================================
--- symfile.c	(revision 45)
+++ symfile.c	(revision 46)
@@ -87,8 +87,6 @@ static int simple_read_overlay_region_ta
 static void simple_free_overlay_region_table (void);
 #endif
 
-static void set_initial_language (void);
-
 static void load_command (char *, int);
 
 static void symbol_file_add_main_1 (char *args, int from_tty, int flags);
@@ -1576,7 +1574,7 @@ symbol_file_command (char *args, int fro
    stabs we find, but we can't do that until later when we read in
    full symbols.  */
 
-static void
+void
 set_initial_language (void)
 {
   struct partial_symtab *pst;
Index: symfile.h
===================================================================
--- symfile.h	(revision 45)
+++ symfile.h	(revision 46)
@@ -292,6 +292,8 @@ extern int auto_solib_limit;
 
 /* From symfile.c */
 
+extern void set_initial_language (void);
+
 extern struct partial_symtab *allocate_psymtab (char *, struct objfile *);
 
 extern void discard_psymtab (struct partial_symtab *);
Index: language.c
===================================================================
--- language.c	(revision 45)
+++ language.c	(revision 46)
@@ -43,6 +43,7 @@
 #include "parser-defs.h"
 #include "jv-lang.h"
 #include "demangle.h"
+#include "symfile.h"
 
 extern void _initialize_language (void);
 
@@ -185,11 +186,14 @@ local or auto    Automatic setting based
 	  /* Found it!  Go into manual mode, and use this language.  */
 	  if (languages[i]->la_language == language_auto)
 	    {
-	      /* Enter auto mode.  Set to the current frame's language, if known.  */
+	      /* Enter auto mode.  Set to the current frame's language, if
+                 known, or fallback to the initial language.  */
 	      language_mode = language_mode_auto;
 	      flang = get_frame_language ();
 	      if (flang != language_unknown)
 		set_language (flang);
+	      else
+		set_initial_language ();
 	      expected_language = current_language;
 	      return;
 	    }
Index: Makefile.in
===================================================================
--- Makefile.in	(revision 45)
+++ Makefile.in	(revision 46)
@@ -2323,7 +2323,7 @@ jv-valprint.o: jv-valprint.c $(defs_h) $
 	$(language_h) $(jv_lang_h) $(c_lang_h) $(annotate_h) $(gdb_string_h)
 language.o: language.c $(defs_h) $(gdb_string_h) $(symtab_h) $(gdbtypes_h) \
 	$(value_h) $(gdbcmd_h) $(expression_h) $(language_h) $(target_h) \
-	$(parser_defs_h) $(jv_lang_h) $(demangle_h)
+	$(parser_defs_h) $(jv_lang_h) $(demangle_h) $(symfile_h)
 libunwind-frame.o: libunwind-frame.c $(defs_h) $(inferior_h) $(frame_h) \
 	$(frame_base_h) $(frame_unwind_h) $(gdbcore_h) $(gdbtypes_h) \
 	$(symtab_h) $(objfiles_h) $(regcache_h) $(gdb_assert_h) \

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Index: gdb.base/set_lang_auto.exp
===================================================================
--- gdb.base/set_lang_auto.exp	(revision 0)
+++ gdb.base/set_lang_auto.exp	(revision 47)
@@ -0,0 +1,70 @@
+# Copyright 2008 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
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if $tracelevel then {
+    strace $tracelevel
+}
+
+set prms_id 0
+set bug_id 0
+
+set testfile start
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    untested "Couldn't compile test program"
+    return -1
+}
+
+# Get things started.
+
+gdb_exit
+gdb_start
+gdb_reinitialize_dir $srcdir/$subdir
+gdb_load ${binfile}
+
+# Do not run the inferior as the purpose of this testcase is to test
+# the behavior of the "set language" command when there is no inferior.
+
+# Check the language after the binary has been loaded.  It should be
+# "auto; currently c".
+gdb_test "show lang" \
+         "The current source language is \"auto; currently c\"\\." \
+         "show lang after loading binary"
+
+# Now, switch the language to a specific language, instead of leaving it
+# on auto.
+gdb_test "set lang ada" \
+         "" \
+         "forcing the language to ada"
+
+# Verify that the language is now "ada".
+gdb_test "show lang" \
+         "The current source language is \"ada\"\\." \
+         "show lang after switching language to ada"
+
+# Then, switch back to auto...
+gdb_test "set lang auto" \
+         "" \
+         "switching the language back to auto"
+
+# ... And verify that the language mode is back to auto *and* that
+# the selected language is C.
+
+gdb_test "show lang" \
+         "The current source language is \"auto; currently c\"\\." \
+         "show lang after having switched back to auto"
+
+