[Ada] avoid error message pollution with uninitialized tagged variable

Consider the following function...

  3 procedure Foo is
  4    I : Integer := Ident (10);
  5    Obj : Base;
  6 begin
  7    Obj.X := I;
  8    Do_Nothing (Obj.X'Address);
  9 end Foo;

... where type "Base" is defined as a plain tagged record. If the user
stops execution before "Obj" gets initialized (for example, by inserting
a breakpoint "on" the function - or in other words, by inserting a
breakpoint using the function name as the location), one might get
the following of output if you try printing the value of obj:

    (gdb) p obj
    object size is larger than varsize-limit
    object size is larger than varsize-limit
    object size is larger than varsize-limit
    $1 = object size is larger than varsize-limit
    (x => 4204154)

Same thing with "info locals":

   (gdb) info locals
    i = 0
    obj = object size is larger than varsize-limit
    (x => 4204154)

We have also seen different error messages such as "Cannot read
memory at 0x...".

The error happens because we are trying to read the dispatch table
of a tagged type variable before it gets initialized.  So the errors
might legitimately occur, and are supposed to be be contained.
However, the way things are written in ada-lang.c:ada_tag_name,
although the exception is in fact contained, the error message still
gets to be printed out.

This patch prevents this from happening by eliminating the use of
catch_errors, and using a TRY_CATCH block instead.  Doing this removed
the need to use functions specifically fitted for catch_errors, and
thus some other simplifications could me made.  In the end, the code
got reorganized a bit to better show the logic behind it, as well as
the common patterns.

gdb/ChangeLog:

        * ada-lang.c (struct tag_args): Delete.
        (ada_get_tsd_type): Function body moved up in source file.
        (ada_tag_name_1, ada_tag_name_2): Delete.
        (ada_get_tsd_from_tag): New function.
        (ada_tag_name_from_tsd): New function.
        (ada_tag_name): Use a TRY_CATCH block instead of catch_errors
        to determine the tag name.

gdb/testsuite/ChangeLog:

        * gdb.ada/tagged_not_init: New testcase.

4 files changed, 117 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.ada/tagged_not_init.exp b/gdb/testsuite/gdb.ada/tagged_not_init.exp
new file mode 100644
index 0000000..013d76a
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/tagged_not_init.exp
@@ -0,0 +1,36 @@
+# Copyright 2012 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/>.
+
+load_lib "ada.exp"
+
+if { [skip_ada_tests] } { return -1 }
+
+set testdir "tagged_not_init"
+set testfile "${testdir}/foo"
+set srcfile ${srcdir}/${subdir}/${testfile}.adb
+set binfile ${objdir}/${subdir}/${testfile}
+
+file mkdir ${objdir}/${subdir}/${testdir}
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable {debug}] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/foo.adb]
+runto "foo.adb:$bp_location"
+
+gdb_test "print obj" " = \\(x => -?$decimal\\)"
+
diff --git a/gdb/testsuite/gdb.ada/tagged_not_init/foo.adb b/gdb/testsuite/gdb.ada/tagged_not_init/foo.adb
new file mode 100644
index 0000000..aa345a2
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/tagged_not_init/foo.adb
@@ -0,0 +1,24 @@
+--  Copyright 2012 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/>.
+
+with Pck; use Pck;
+
+procedure Foo is
+   I : Integer := Ident (10);  -- STOP
+   Obj : Base;
+begin
+   Obj.X := I;
+   Do_Nothing (Obj.X'Address);
+end Foo;
diff --git a/gdb/testsuite/gdb.ada/tagged_not_init/pck.adb b/gdb/testsuite/gdb.ada/tagged_not_init/pck.adb
new file mode 100644
index 0000000..5d6e760
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/tagged_not_init/pck.adb
@@ -0,0 +1,26 @@
+--  Copyright 2012 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/>.
+
+package body Pck is
+   function Ident (I : Integer) return Integer is
+   begin
+      return I;
+   end Ident;
+
+   procedure Do_Nothing (A : System.Address) is
+   begin
+      null;
+   end Do_Nothing;
+end Pck;
diff --git a/gdb/testsuite/gdb.ada/tagged_not_init/pck.ads b/gdb/testsuite/gdb.ada/tagged_not_init/pck.ads
new file mode 100644
index 0000000..19d9295
--- /dev/null
+++ b/gdb/testsuite/gdb.ada/tagged_not_init/pck.ads
@@ -0,0 +1,31 @@
+--  Copyright 2012 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/>.
+
+with System;
+
+package Pck is
+   type Base is tagged record
+      X : Integer := 42;
+   end record;
+
+   type Extension is new Base with
+      record
+         Y : Float := 42.0;
+      end record;
+
+   function Ident (I : Integer) return Integer;
+
+   procedure Do_Nothing (A : System.Address);
+end Pck;