gdb/testsuite/gdb.dwarf2/locexpr-data-member-location.exp

# Copyright 2021 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 case uses the DWARF assembler to reproduce the problem
# described by PR28030.  The bug turned out to be that
# FIELD_LOC_KIND_DWARF_BLOCK was not handled when recursively copying
# a value's type when preserving the value history during the freeing
# up of objfiles associated with a shared object.  (Yes, figuring out
# how to make this happen in a concise test case turned out to be
# challenging.)
#
# The following elements proved to be necessary for reproducing the
# problem:
#
# 1) A location expression needed to be used with
#    DW_AT_data_member_location rather than a simple offset.
#    Moreover, this location expression needed to use opcodes
#    which GDB's DWARF reader could not convert to a simple
#    offset.  (Note, however, that GDB could probably be improved
#    to handle the opcodes chosen for this test; if decode_locdesc()
#    in dwarf2/read.c is ever updated to handle both DW_OP_pick and
#    DW_OP_drop, then this test could end up passing even if
#    the bug it's intended to test has not been fixed.)
#
# 2) The debug info containing the above DWARF info needed
#    to be associated with a shared object since the problem
#    occurred while GDB was preserving values during the
#    purging of shared objects.
#
# 3) After performing some simple gdb commands, the program is
#    run again.  In the course of running the objfile destructor
#    associated with the shared object, values are preserved
#    along with their types.  As noted earlier, it was during
#    the recursive type copy that the bug was observed.
#
# Therefore, due to #2 above, this test case creates debug info
# which is then used by a shared object.

# This test can't be run on targets lacking shared library support.
if [skip_shlib_tests] {
    return 0
}

load_lib dwarf.exp

# This test can only be run on targets which support DWARF-2 and use gas.
if ![dwarf2_support] {
    return 0
}

# gdb_test_file_name is the name of this file without the .exp
# extension.  Use it to form basenames for the main program
# and shared object.
set main_basename ${::gdb_test_file_name}-main
set lib_basename ${::gdb_test_file_name}-lib

# We're generating DWARF assembly for the shared object; therefore,
# the source file for the library / shared object must be listed first
# (in the standard_testfile invocation) since ${srcfile} is used by
# get_func_info (for determining the start, end, and length of a
# function).
#
# The output of Dwarf::assemble will be placed in $lib_basename.S
# which will be ${srcfile3} after the execution of standard_testfile.

standard_testfile $lib_basename.c $main_basename.c $lib_basename.S

set libsrc "${::srcdir}/${::subdir}/${::srcfile}"
set lib_so [standard_output_file ${lib_basename}.so]
set asm_file [standard_output_file ${::srcfile3}]

# We need to know the size of some types in order to write some of the
# debugging info that we're about to generate.  For that, we ask GDB
# by debugging the shared object associated with this test case.

# Compile the shared library: -DIS_SHAREDLIB prevents main() from
# being defined.  Note that debugging symbols will be present for
# this compilation.
if {[gdb_compile_shlib $libsrc $lib_so \
                       {additional_flags=-DIS_SHAREDLIB debug}] != ""} {
    untested "failed to compile shared library"
    return
}

# Start a fresh GDB and load the shared library.
clean_restart $lib_so

# Using our running GDB session, determine sizes of several types.
set long_size [get_sizeof "long" -1]
set addr_size [get_sizeof "void *" -1]
set struct_A_size [get_sizeof "g_A" -1]
set struct_B_size [get_sizeof "g_B" -1]

if { $long_size == -1 || $addr_size == -1 \
     || $struct_A_size == -1 || $struct_B_size == -1} {
    perror "Can't determine type sizes"
    return
}

# Retrieve struct offset of MBR in struct TP
proc get_offsetof { tp mbr } {
    return [get_integer_valueof "&((${tp} *) 0)->${mbr}" -1]
}

# Use running GDB session to get struct offsets
set A_a [get_offsetof A a]
set A_x [get_offsetof A x]
set B_a [get_offsetof B a]
set B_b [get_offsetof B b]
set B_x2 [get_offsetof B x2]

# Create the DWARF.
Dwarf::assemble ${asm_file} {
    declare_labels L

    # Find start, end, and length of functions foo and bar.
    # These calls to get_func_info will create and set variables
    # foo_start, bar_start, foo_end, bar_end, foo_len, and
    # bar_len.
    #
    # In order to get the right answers, get_func_info (and,
    # underneath, function_range) should use the same compiler flags
    # as those used to make a shared object.  For any targets that get
    # this far, -fpic is probably correct.
    #
    # Also, it should be noted that IS_SHAREDLIB is NOT defined as one
    # of the additional flags.  Not defining IS_SHAREDLIB will cause a
    # main() to be defined for the compilation of the shared library
    # source file which happens as a result of using get_func_info;
    # this is currently required in order to this facility.
    set flags {additional_flags=-fpic debug}
    get_func_info foo $flags
    get_func_info bar $flags

    cu { label cu_label } {
	DW_TAG_compile_unit {
	    {DW_AT_language @DW_LANG_C_plus_plus}
	    {name ${::srcfile}}
	    {stmt_list $L DW_FORM_sec_offset}
        } {
	    declare_labels int_label class_A_label class_B_label \
	                   B_ptr_label

	    int_label: DW_TAG_base_type {
		{DW_AT_byte_size ${::long_size} DW_FORM_udata}
		{DW_AT_encoding @DW_ATE_signed}
		{DW_AT_name "int"}
	    }

	    class_A_label: DW_TAG_class_type {
		{DW_AT_name "A"}
		{DW_AT_byte_size ${::struct_A_size} DW_FORM_sdata}
	    } {
		DW_TAG_member {
		    {DW_AT_name "a"}
		    {DW_AT_type :$int_label}
		    {DW_AT_data_member_location ${::A_a} DW_FORM_udata}
		}
		DW_TAG_member {
		    {DW_AT_name "x"}
		    {DW_AT_type :$int_label}
		    {DW_AT_data_member_location ${::A_x} DW_FORM_udata}
		}
	    }

	    class_B_label: DW_TAG_class_type {
		{DW_AT_name "B"}
		{DW_AT_byte_size ${::struct_B_size} DW_FORM_sdata}
	    } {
		# While there are easier / better ways to specify an
		# offset used by DW_AT_data_member_location than that
		# used below, we need a location expression here in
		# order to reproduce the bug.  Moreover, this location
		# expression needs to use opcodes that aren't handled
		# by decode_locdesc() in dwarf2/read.c; if we use
		# opcodes that _are_ handled by that function, the
		# location expression will be converted into a simple
		# offset - which will then (again) not reproduce the
		# bug.  At the time that this test was written,
		# neither DW_OP_pick nor DW_OP_drop were being handled
		# by decode_locdesc(); this is why those opcodes were
		# chosen.
		DW_TAG_inheritance {
		    {DW_AT_type :$class_A_label}
		    {DW_AT_data_member_location {
			DW_OP_constu ${::B_a}
			DW_OP_plus
			DW_OP_pick 0
			DW_OP_drop} SPECIAL_expr}
		    {DW_AT_accessibility 1 DW_FORM_data1}
		}
		DW_TAG_member {
		    {DW_AT_name "b"}
		    {DW_AT_type :$int_label}
		    {DW_AT_data_member_location ${::B_b} DW_FORM_udata}
		}
		DW_TAG_member {
		    {DW_AT_name "x2"}
		    {DW_AT_type :$int_label}
		    {DW_AT_data_member_location ${::B_x2} DW_FORM_udata}
		}
	    }

	    B_ptr_label: DW_TAG_pointer_type {
		{DW_AT_type :$class_B_label}
		{DW_AT_byte_size ${::addr_size} DW_FORM_sdata}
	    }

	    DW_TAG_variable {
		{DW_AT_name "g_A"}
		{DW_AT_type :$class_A_label}
		{DW_AT_external 1 flag}
		{DW_AT_location {DW_OP_addr [gdb_target_symbol "g_A"]} \
		                 SPECIAL_expr}
	    }

	    DW_TAG_variable {
		{DW_AT_name "g_B"}
		{DW_AT_type :$class_B_label}
		{DW_AT_external 1 flag}
		{DW_AT_location {DW_OP_addr [gdb_target_symbol "g_B"]} \
		                 SPECIAL_expr}
	    }

	    # We can't use MACRO_AT for the definitions of foo and bar
	    # because it doesn't provide a way to pass the appropriate
	    # flags.  Therefore, we list the name, low_pc, and high_pc
	    # explicitly.
	    DW_TAG_subprogram {
		{DW_AT_name foo}
		{DW_AT_low_pc $foo_start DW_FORM_addr}
		{DW_AT_high_pc $foo_end DW_FORM_addr}
		{DW_AT_type :${B_ptr_label}}
		{DW_AT_external 1 flag}
	    }

	    DW_TAG_subprogram {
		{DW_AT_name bar}
		{DW_AT_low_pc $bar_start DW_FORM_addr}
		{DW_AT_high_pc $bar_end DW_FORM_addr}
		{DW_AT_type :${B_ptr_label}}
		{DW_AT_external 1 flag}
	    } {
		DW_TAG_formal_parameter {
		    {DW_AT_name v}
		    {DW_AT_type :${B_ptr_label}}
		}
	    }
	}
    }

    lines {version 2} L {
	include_dir "${::srcdir}/${::subdir}"
	file_name "${::srcfile}" 1

	# Generate a line table program.
	program {
	    {DW_LNE_set_address $foo_start}
	    {line [gdb_get_line_number "foo prologue"]}
	    {DW_LNS_copy}
	    {DW_LNE_set_address foo_label}
	    {line [gdb_get_line_number "foo return"]}
	    {DW_LNS_copy}
	    {line [gdb_get_line_number "foo end"]}
	    {DW_LNS_copy}
	    {DW_LNE_set_address $foo_end}
	    {DW_LNS_advance_line 1}
	    {DW_LNS_copy}
	    {DW_LNE_end_sequence}

	    {DW_LNE_set_address $bar_start}
	    {line [gdb_get_line_number "bar prologue"]}
	    {DW_LNS_copy}
	    {DW_LNE_set_address bar_label}
	    {line [gdb_get_line_number "bar return"]}
	    {DW_LNS_copy}
	    {line [gdb_get_line_number "bar end"]}
	    {DW_LNS_copy}
	    {DW_LNE_set_address $bar_end}
	    {DW_LNS_advance_line 1}
	    {DW_LNS_copy}
	    {DW_LNE_end_sequence}
	}
    }

    aranges {} cu_label {
	arange {} $foo_start $foo_end
	arange {} $bar_start $bar_end
    }
}

# Compile the shared object again, but this time include / use the
# DWARF info that we've created above.  Note that (again)
# -DIS_SHAREDLIB is used to prevent inclusion of main() in the shared
# object.  Also note the use of the "nodebug" option.  Any debugging
# information that we need will be provided by the DWARF info created
# above.
if {[gdb_compile_shlib [list $libsrc $asm_file] $lib_so \
                       {additional_flags=-DIS_SHAREDLIB nodebug}] != ""} {
    untested "failed to compile shared library"
    return
}

# Compile the main program for use with the shared object.
if [prepare_for_testing "failed to prepare" ${testfile} \
                        ${::srcfile2} [list debug shlib=$lib_so]] {
    return -1
}

# Do whatever is necessary to make sure that the shared library is
# loaded for remote targets.
gdb_load_shlib ${lib_so}

if ![runto_main] then {
    return
}

# Step into foo so that we can finish out of it.
gdb_test "step" "foo .. at .* foo end.*" "step into foo"

# Finishing out of foo will create a value that will later need to
# be preserved when restarting the program.
gdb_test "finish" "= \\(class B \\*\\) ${::hex} .*" "finish out of foo"

# Dereferencing and printing the return value isn't necessary
# for reproducing the bug, but we should make sure that the
# return value is what we expect it to be.
gdb_test "p *$" { = {<A> = {a = 8, x = 9}, b = 10, x2 = 11}} \
         "dereference return value"

# The original PR28030 reproducer stepped back into the shared object,
# so we'll do the same here:
gdb_test "step" "bar \\(.*" "step into bar"

# We don't want a clean restart here since that will be too clean.
# The original reproducer for PR28030 set a breakpoint in the shared
# library and then restarted via "run".  The command below does roughly
# the same thing.  It's at this step that an internal error would
# occur for PR28030.  The "message" argument tells runto to turn on
# the printing of PASSes while runto is doing its job.
runto "bar" message