[patchv2] Fix internal error on DW_OP_bregx(-1)

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Mon, 19 Oct 2015 18:41:51 +0200, Pedro Alves wrote:
> Please write this using the Dwarf assembler.

Done.

OK for commit?


Thanks,
Jan

gdb/ChangeLog
2015-10-12  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* findvar.c (address_from_register): Check REGNUM validity.

gdb/testsuite/ChangeLog
2015-10-20  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Pedro Alves  <palves@redhat.com>

	* gdb.dwarf2/dw2-regno-invalid.exp: New file.
	* lib/dwarf.exp (Dwarf): Add DW_OP_bregx.

diff --git a/gdb/findvar.c b/gdb/findvar.c
index 0f46e53..855947d 100644
--- a/gdb/findvar.c
+++ b/gdb/findvar.c
@@ -927,6 +927,12 @@ address_from_register (int regnum, struct frame_info *frame)
   struct type *type = builtin_type (gdbarch)->builtin_data_ptr;
   struct value *value;
   CORE_ADDR result;
+  int regnum_max_excl = (gdbarch_num_regs (gdbarch)
+			 + gdbarch_num_pseudo_regs (gdbarch));
+
+  if (regnum < 0 || regnum >= regnum_max_excl)
+    error (_("Invalid register #%d, expecting 0 <= # < %d"), regnum,
+	   regnum_max_excl);
 
   /* This routine may be called during early unwinding, at a time
      where the ID of FRAME is not yet known.  Calling value_from_register
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.exp b/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.exp
new file mode 100644
index 0000000..a7d77c5
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.exp
@@ -0,0 +1,71 @@
+# Copyright 2015 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 dwarf.exp
+
+# Test GDB does not internal error on DWARF register number -1 which is invalid
+# in DWARF.  clang-3.5.0-9.fc22.x86_64 produced it inside DW_AT_location.
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+standard_testfile .S main.c
+
+# Make some DWARF for the test.
+set asm_file [standard_output_file $srcfile]
+Dwarf::assemble $asm_file {
+    cu {} {
+	compile_unit {
+	    {low_pc main DW_FORM_addr}
+	    {high_pc main+0x10000 DW_FORM_addr}
+	} {
+	    declare_labels integer_label
+
+	    integer_label: DW_TAG_base_type {
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+		{DW_AT_encoding  @DW_ATE_signed}
+		{DW_AT_name      integer}
+	    }
+
+	    DW_TAG_subprogram {
+		{name main}
+		{DW_AT_external 1 flag}
+		{low_pc main DW_FORM_addr}
+		{high_pc main+0x10000 DW_FORM_addr}
+	    } {
+		DW_TAG_variable {
+		    {DW_AT_name bregx}
+			{DW_AT_type :$integer_label}
+			{DW_AT_external 1 flag}
+		    {DW_AT_location {
+			DW_OP_bregx 0xffffffff 0
+		    } SPECIAL_expr}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+			  [list $srcfile2 $asm_file] {nodebug}] } {
+    return -1
+}
+
+runto_main
+
+# Variable 'bregx' needs to be inside main as for global symbols GDB does not
+# support non-trivial DW_AT_location.  Former GDB printed internal error here.
+gdb_test "p bregx"
diff --git a/gdb/testsuite/lib/dwarf.exp b/gdb/testsuite/lib/dwarf.exp
index 515334e..888ba94 100644
--- a/gdb/testsuite/lib/dwarf.exp
+++ b/gdb/testsuite/lib/dwarf.exp
@@ -901,6 +901,11 @@ namespace eval Dwarf {
 		    _op .byte [lindex $line 1]
 		}
 
+		DW_OP_bregx {
+		    _op .uleb128 [lindex $line 1]
+		    _op .sleb128 [lindex $line 2]
+		}
+
 		default {
 		    if {[llength $line] > 1} {
 			error "Unimplemented: operands in location for $opcode"