[PATCH] Show optimized out local variables in "info locals"

Simon Marchi
2017-11-14T17:08:31Z

Currently, optimized out variables are not shown when doing "info
locals". Some users found that confusing, thinking GDB forgot to print
their variable. This patch adds them to the "info locals" output. I
added a test in gdb.dwarf2 to test for that behavior. I think doing a
synthetic DWARF test is the easiest way to have an optimized out local
variable for sure.

However, this change reveals what I think is a bug in GDB, see:

http://lists.dwarfstd.org/pipermail/dwarf-discuss-dwarfstd.org/2017-September/004394.html

This patch marks the tests in inline-locals.exp that start failing as
KFAIL. I'd like to tackle this bug eventually, but I don't have the
time right now. I think it's still better to show an extra erroneous
entry than to not show the optimized out variables at all. I haven't
created a bug in bugzilla yet, but if we agree it's indeed a bug, I'll
create one and update the setup_kfail lines with the actual bug number
before pushing.

gdb/ChangeLog:

* stack.c (iterate_over_block_locals): Add LOC_OPTIMIZED_OUT
case in switch.

gdb/testsuite/ChangeLog:

* gdb.opt/inline-locals.exp: Mark tests as KFAIL.
* gdb.dwarf2/info-locals-optimized-out.exp: New file.
* gdb.dwarf2/info-locals-optimized-out.c: New file.
---
gdb/stack.c | 1 +
.../gdb.dwarf2/info-locals-optimized-out.c | 23 +++++++
.../gdb.dwarf2/info-locals-optimized-out.exp | 74 ++++++++++++++++++++++
gdb/testsuite/gdb.opt/inline-locals.exp | 2 +
4 files changed, 100 insertions(+)
create mode 100644 gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.c
create mode 100644 gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.exp

diff --git a/gdb/stack.c b/gdb/stack.c
index 81032fc..6bd0d45 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -1922,6 +1922,7 @@ iterate_over_block_locals (const struct block *b,
case LOC_REGISTER:
case LOC_STATIC:
case LOC_COMPUTED:
+ case LOC_OPTIMIZED_OUT:
if (SYMBOL_IS_ARGUMENT (sym))
break;
if (SYMBOL_DOMAIN (sym) == COMMON_BLOCK_DOMAIN)
diff --git a/gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.c b/gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.c
new file mode 100644
index 0000000..e3ae4cd
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.c
@@ -0,0 +1,23 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2017 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/>. */
+
+int
+main (void)
+{
+ asm ("main_label: .globl main_label");
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.exp b/gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.exp
new file mode 100644
index 0000000..dd0a99b
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/info-locals-optimized-out.exp
@@ -0,0 +1,74 @@
+# Copyright 2017 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/>.
+
+# Test that "info locals" shows optimized out variables.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+ return 0
+}
+
+standard_testfile .c ${gdb_test_file_name}-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ global srcdir subdir srcfile
+ global dwarf_regnum regname
+
+ set buf_var [gdb_target_symbol buf]
+
+ cu {} {
+ DW_TAG_compile_unit {
+ {DW_AT_name info-locals-optimized-out.c}
+ {DW_AT_comp_dir /tmp}
+ } {
+ declare_labels int_type_label
+
+ # int
+ int_type_label: base_type {
+ {name "int"}
+ {encoding @DW_ATE_signed}
+ {byte_size 4 DW_FORM_sdata}
+ }
+
+ DW_TAG_subprogram {
+ {MACRO_AT_func { main ${srcdir}/${subdir}/${srcfile} }}
+ {DW_AT_external 1 flag}
+ } {
+ # A variable completely optimized out.
+ DW_TAG_variable {
+ {name "opt_out"}
+ {type :$int_type_label}
+ }
+ }
+ }
+ }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+ [list $srcfile $asm_file] {nodebug}] } {
+ return -1
+}
+
+if ![runto_main] {
+ return -1
+}
+
+# Make sure "info locals" shows optimized out variables.
+gdb_test "info locals" ".*opt_out = <optimized out>.*" "info local shows optimized out variable"
diff --git a/gdb/testsuite/gdb.opt/inline-locals.exp b/gdb/testsuite/gdb.opt/inline-locals.exp
index 76463a6..7245df7 100644
--- a/gdb/testsuite/gdb.opt/inline-locals.exp
+++ b/gdb/testsuite/gdb.opt/inline-locals.exp
@@ -43,6 +43,7 @@ if { ! $no_frames } {
"backtrace from bar 2"
gdb_test "up" "#1 .*func1 .* at .*" "up from bar 2"
gdb_test "info frame" ".*inlined into frame.*" "func1 inlined 2"
+ setup_kfail "gdb/xyz" *-*-*
gdb_test "info locals" "array = {.*}" "info locals above bar 2"

set msg "info args above bar 2"
@@ -82,6 +83,7 @@ if { ! $no_frames } {
"backtrace from bar 3"
gdb_test "up" "#1 .*func1 .* at .*" "up from bar 3"
gdb_test "info frame" ".*inlined into frame.*" "func1 inlined 3"
+ setup_kfail "gdb/xyz" *-*-*
gdb_test "info locals" "array = {.*}" "info locals above bar 3"

set msg "info args above bar 3"
--
2.7.4