Re: [PATCH v2 1/2] Optzd-out ptr: New test for error handling

[Don Breazeal <donb at codesourcery dot com>]

On 3/29/2016 4:57 AM, Yao Qi wrote:
> Don Breazeal <donb@codesourcery.com> writes:
> 
>> +		DW_TAG_subprogram {
>> +		    {DW_AT_name func01}
>> +		    {DW_AT_type :$int_label}
>> +		    {external   1 flag}
>> +		    {low_pc     func01_start addr}
>> +		    {high_pc    func01_end addr}
> 
> Please use MACRO_AT_func so that the low_pc and high_pc can be got correctly.
> 
>> +		} {
>> +		    DW_TAG_variable {
>> +			{DW_AT_name ptr}
>> +			{DW_AT_type :$pointer_label}
>> +			{DW_AT_location {} DW_FORM_block1}
>> +		    }
>> +		}
>> +    
>> +		DW_TAG_subprogram {
>> +		    {DW_AT_name main}
>> +		    {DW_AT_type :$int_label}
>> +		    {external   1 flag}
>> +		    {low_pc     main_start addr}
>> +		    {high_pc    main_end addr}
> 
> Likewise.
> 
>> +		} {
>> +		}
> 
Hi Yao,
Here is the patch updated to use MACRO_AT_func.
Thanks,
--Don
----
This patch implements a test that ensures that with "set print object
on", -var-create returns "<optimized out>" for an optimized out pointer
to structure, rather than throwing an error, while also ensuring that
any attempt to dereference the pointer *will* throw an error.

It uses the dwarf assembler to construct the appropriate debug info
to represent a pointer-to-struct in the program as optimized out,
and then accesses that pointer in various ways.  The test uses both
the console interpreter and the MI interpreter.

Tested on native Linux x86_64.

2016-03-29  Don Breazeal  <donb@codesourcery.com>

	* gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.c: New test program.
	* gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.exp: New test script.

---
 gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.c   |  41 ++++
 gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.exp | 250
+++++++++++++++++++++++++
 2 files changed, 291 insertions(+)

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.c
b/gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.c
new file mode 100644
index 0000000..ff6fae0
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.c
@@ -0,0 +1,41 @@
+/* Copyright 2016 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+struct foo
+{
+  int a;
+  int x[5];
+  struct foo *y;
+};
+
+void
+func01 (void)
+{
+  struct foo *ptr;
+
+  asm ("func01_label: .globl func01_label");
+  ptr = (struct foo *) 0x0;
+  return;
+}
+
+int
+main ()
+{
+  asm ("main_label: .globl main_label");
+  func01 ();
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.exp
b/gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.exp
new file mode 100644
index 0000000..44f1df1
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-opt-structptr.exp
@@ -0,0 +1,250 @@
+# Copyright 2016 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/>.
+
+# This test ensures that with "set print object on", -var-create will
+# return "<optimized out>" for an optimized out pointer to structure,
+# rather than attempting to dereference the pointer to determine its
+# actual type (instead of its declared type).  We want to test that GDB
+# can display such a pointer without throwing an error, while also
+# ensuring that any attempt to dereference the pointer *will* throw an
+# error.
+
+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 dw2-opt-structptr.c dw2-opt-structptr-dw.S
+
+# Generate a test program with dwarf information showing the variable
+# 'ptr', a pointer-to-struct, as optimized out.  The dwarf will also
+# describe the structure as have a scalar, array, and pointer-to-struct
+# members.
+
+proc build_test_program {} {
+    global testfile srcfile srcfile2
+
+    # Make some DWARF for the test.
+    set asm_file [standard_output_file $srcfile2]
+    Dwarf::assemble $asm_file {
+        global srcdir subdir srcfile
+
+	# Creating a CU with 4-byte addresses lets this test link on
+	# both 32- and 64-bit machines.
+	cu { addr_size 4 } {
+
+	    DW_TAG_compile_unit {
+		{DW_AT_language @DW_LANG_C99}
+		{DW_AT_name     dw2-opt-structptr.c}
+		{DW_AT_comp_dir /tmp}
+	    } {
+		declare_labels int_label struct_label pointer_label \
+			       array_label
+
+		int_label: DW_TAG_base_type {
+		    {DW_AT_byte_size 4 DW_FORM_sdata}
+		    {DW_AT_encoding  @DW_ATE_signed}
+		    {DW_AT_name      integer}
+		}
+
+		array_label: DW_TAG_array_type {
+		    {DW_AT_name foo__array_type}
+		    {DW_AT_type :$int_label}
+		} {
+		    DW_TAG_subrange_type {
+			{DW_AT_type	   :$int_label}
+			{DW_AT_lower_bound 0   DW_FORM_data1}
+			{DW_AT_upper_bound 127 DW_FORM_data1}
+		    }
+		}
+
+		struct_label: DW_TAG_structure_type {
+		    {DW_AT_name "foo"}
+		    {DW_AT_byte_size 12 DW_FORM_sdata}
+		} {
+		    member {
+			{name a}
+			{type :$int_label}
+			{data_member_location 0 data1}
+		    }
+		    member {
+			{name x}
+			{type :$array_label}
+			{data_member_location 4 data1}
+		    }
+		    member {
+			{name y}
+			{type :$pointer_label}
+			{data_member_location 8 data1}
+		    }
+		}
+
+		pointer_label: DW_TAG_pointer_type {
+		    {DW_AT_byte_size 4 DW_FORM_sdata}
+		    {DW_AT_type  :$struct_label}
+		}
+
+		DW_TAG_subprogram {
+		    {DW_AT_name func01}
+		    {DW_AT_type :$int_label}
+		    {external   1 flag}
+		    {MACRO_AT_func {func01 ${srcdir}/${subdir}/${srcfile}}}
+		} {
+		    DW_TAG_variable {
+			{DW_AT_name ptr}
+			{DW_AT_type :$pointer_label}
+			{DW_AT_location {} DW_FORM_block1}
+		    }
+		}
+
+		DW_TAG_subprogram {
+		    {DW_AT_name main}
+		    {DW_AT_type :$int_label}
+		    {external   1 flag}
+		    {MACRO_AT_func {main ${srcdir}/${subdir}/${srcfile}}}
+		} {
+		}
+	    }
+	}
+    }
+
+    set sources "$srcfile $asm_file"
+    if {[build_executable $testfile.exp $testfile $sources {nodebug}]} {
+	untested $testfile.exp
+	return -1
+    }
+}
+
+# Test access to an optimized-out pointer-to-struct using the
+# console interpreter.
+
+proc do_console_test {} {
+    global binfile
+
+    clean_restart $binfile
+
+    with_test_prefix "console" {
+	gdb_test_no_output "set print object on"
+
+	if {![runto_main]} {
+	    return -1
+	}
+
+	if {![runto func01]} {
+	    return -1
+	}
+	
+	gdb_test "info addr ptr" "Symbol \"ptr\" is optimized out."
+	
+	gdb_test "print ptr" "<optimized out>"
+	
+	gdb_test "print *ptr" "value has been optimized out"
+	
+	gdb_test "print ptr->a" "value has been optimized out"
+	
+	gdb_test "print ptr->x" "value has been optimized out"
+	
+	gdb_test "print ptr->y" "value has been optimized out"
+    }
+}
+
+# Test access to an optimized-out pointer-to-struct using the
+# MI interpreter.
+
+proc do_mi_test {} {
+
+    load_lib mi-support.exp
+    set MIFLAGS "-i=mi"
+
+    global mi_gdb_prompt
+    global srcdir
+    global subdir
+    global binfile
+
+    with_test_prefix "mi" {
+	gdb_exit
+	if {[mi_gdb_start]} {
+	    return -1
+	}
+	
+	mi_delete_breakpoints
+	mi_gdb_reinitialize_dir $srcdir/$subdir
+	mi_gdb_load $binfile
+	
+	# This causes GDB to dereference a pointer-to-structure when doing
+	# -var-create.
+	mi_gdb_test "-gdb-set print object on" ".*" "set print object on"
+	
+	mi_gdb_test "-break-insert main" ".*" "insert breakpoint main"
+	mi_gdb_test "-break-insert func01" ".*" "insert breakpoint func01"
+	
+	# Run to main.  Use an explicit expect here since the limited
+	# debug info will result in output that isn't handled by the
+	# MI test utilities.
+	set test "run to main"
+	mi_run_cmd
+	gdb_expect {
+	    -re
"\\*stopped,reason=\"breakpoint-hit\".*func=\"main\".*$mi_gdb_prompt$" {
+		pass "$test"
+	    }
+	    timeout {
+		fail "$test (timeout)"
+	    }
+	}
+	
+	# Run to func01.  Use an explicit expect here as above.
+	set test "continue to func01"
+	mi_send_resuming_command "exec-continue" "$test"
+	gdb_expect {
+	    -re
"\\*stopped,reason=\"breakpoint-hit\".*func=\"func01\".*$mi_gdb_prompt$" {
+		pass "$test"
+	    }
+	    timeout {
+		fail "$test (timeout)"
+	    }
+	}
+	
+	# Test that -var-create for 'ptr' is successful.
+	mi_create_varobj "var1" "ptr" "create varobj for ptr"
+	
+	# Test that -var-list-children of 'ptr' is successful.
+	mi_list_varobj_children "var1" { \
+	    {var1.a a 0 integer} \
+	    {var1.x x 128 foo__array_type} \
+	    {var1.y y 3 "struct foo \\*"} \
+	} "get children of var1 (ptr)"
+
+	# Test that dereferencing 'ptr' will throw an error.
+	mi_gdb_test "-var-create var2 * &((ptr)->a)" \
+	    "\\^error,msg=\"value has been optimized out\"" \
+	    "throw error, dereference ptr to access integer member "
+
+	# Test that dereferencing 'ptr' will throw an error.
+	mi_gdb_test "-var-create var3 * &((ptr)->x)" \
+	    "\\^error,msg=\"value has been optimized out\"" \
+	    "throw error, dereference ptr to access array member "
+
+	# Test that dereferencing 'ptr' will throw an error.
+	mi_gdb_test "-var-create var4 * &((ptr)->y)" \
+	    "\\^error,msg=\"value has been optimized out\"" \
+	    "throw error, dereference ptr to access pointer member "
+    }
+}
+
+build_test_program
+do_console_test
+do_mi_test
-- 
1.8.1.1