binutils-gdb/gdb/testsuite/gdb.cp/pass-by-ref.exp
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# Copyright 2007-2022 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/>.
# Check that GDB can call C++ functions whose parameters have
# object type, and are either passed by value or implicitly by reference.
#
# Suppose F is a function that has a call-by-value parameter whose
# type is class C. When calling F with an argument A, a copy of A should
# be created and passed to F. If C is a trivially-copyable type, A can
# be copied by a straightforward memory copy. However, roughly speaking,
# if C has a user-defined copy constructor and/or a user-defined
# destructor, the copy ctor should be used to initialize the copy of A
# before calling F, and a reference to that copy is passed to F. After
# the function returns, the destructor should be called to destruct the
# copy. In this case, C is said to be a 'pass-by-reference' type.
# Determining whether C is pass-by-ref depends on
# how the copy ctor, destructor, and the move ctor of C are defined.
# First of all, C is not copy constructible if its copy constructor is
# explicitly or implicitly deleted. In this case, it would be illegal
# to pass values of type C to a function. C is pass-by-value, if all of
# its copy ctor, dtor, and move ctor are trivially defined.
# Otherwise, it is pass-by-ref.
#
# To cover the many possible combinations, this test generates classes
# that contain three special functions:
# (1) a copy constructor,
# (2) a destructor, and
# (3) a move constructor.
# A special function is in one of the following states:
# * explicit: The function is explicitly defined by the user.
# * defaultedIn: The function is defaulted inside the class decl,
# using the 'default' keyword.
# * defaultedOut: The function is declared inside the class decl,
# and defaulted outside using the 'default' keyword.
# * deleted: The function is explicitly deleted by the user,
# using the 'delete' keyword.
# * absent: The function is not declared by the user (i.e. it does not
# exist in the source. The compiler generates (or deletes) the
# definition in this case.
#
# The C++ ABI decides if a class is pass-by-value or pass-by-ref
# (i.e. trivially copyable or not) first at the language level, based
# on the state of the special functions. Then, at the target level, a
# class may be determined to be pass-by-ref because of its size
# (e.g. if it is too large to fit on registers). For this reason, this
# test generates both a small and a large version for the same
# combination of special function states.
#
# A class is not trivially-copyable if a base class or a field is not
# trivially-copyable, even though the class definition itself seems
# trivial. To test these cases, we also generate derived classes and
# container classes.
#
# The generated code is placed in the test output directory.
#
# The companion test file pass-by-ref-2.exp also contains
# manually-written cases.
if {[skip_cplus_tests]} {
untested "c++ test skipped"
continue
}
# The program source is generated in the output directory.
# We use standard_testfile here to set convenience variables.
standard_testfile .cc
# Some constant values used when generating the source
set SMALL 2
set LARGE 150
set ORIGINAL 2
set CUSTOM 3
set ADDED 4
set TRACE 5
# Return 1 if the class whose special function states are STATES
# is copyable. Otherwise return 0.
proc is_copy_constructible { states } {
set cctor [lindex $states 0]
set dtor [lindex $states 1]
set mctor [lindex $states 2]
if {$cctor == "deleted" || ($cctor == "absent" && $mctor != "absent")} {
return 0
}
return 1
}
# Generate a declaration and an out-of-class definition for a function
# with the provided signature. The STATE should be one of the following:
# - explicit, defaultedIn, defaultedOut, deleted, absent
proc generate_member_function { classname signature length state } {
set declaration ""
set definition ""
global CUSTOM
global TRACE
switch $state {
explicit {
set declaration "$signature;\n"
set definition "$classname\:\:$signature
{
data\[0\] = $CUSTOM;
data\[[expr $length - 1]\] = $CUSTOM;
tracer = $TRACE;
}\n"
}
defaultedIn {
set declaration "$signature = default;\n"
}
defaultedOut {
set declaration "$signature;\n"
set definition "$classname\:\:$signature = default;\n"
}
deleted {
set declaration "$signature = delete;\n"
}
default {
# function is not user-defined in this case
}
}
return [list $declaration $definition]
}
# Generate a C++ class with the given CLASSNAME and LENGTH-many
# integer elements. The STATES is an array of 3 items
# containing the desired state of the special functions
# in this order:
# copy constructor, destructor, move constructor
proc generate_class { classname length states } {
set declarations ""
set definitions ""
set classname "${classname}_[join $states _]"
for {set i 0} {$i < [llength $states]} {incr i} {
set sig ""
switch $i {
0 {set sig "$classname (const $classname \&rhs)"}
1 {set sig "\~$classname (void)"}
2 {set sig "$classname ($classname \&\&rhs)"}
}
set state [lindex $states $i]
set code [generate_member_function $classname $sig $length $state]
append declarations [lindex $code 0]
append definitions [lindex $code 1]
}
global ORIGINAL
return "
/*** C++ class $classname ***/
class ${classname} {
public:
$classname (void);
$declarations
int data\[$length\];
};
$classname\:\:$classname (void)
{
data\[0\] = $ORIGINAL;
data\[[expr $length - 1]\] = $ORIGINAL;
}
$definitions
$classname ${classname}_var; /* global var */
template int cbv<$classname> ($classname arg);"
}
# Generate a small C++ class
proc generate_small_class { states } {
global SMALL
return [generate_class Small $SMALL $states];
}
# Generate a large C++ class
proc generate_large_class { states } {
global LARGE
return [generate_class Large $LARGE $states];
}
# Generate a class that derives from a small class
proc generate_derived_class { states } {
set base "Small_[join $states _]"
set classname "Derived_[join $states _]"
return "
/*** Class derived from $base ***/
class $classname : public $base {
public:
};
$classname ${classname}_var; /* global var */
template int cbv<$classname> ($classname arg);"
}
# Generate a class that contains a small class item
proc generate_container_class { states } {
set contained "Small_[join $states _]"
set classname "Container_[join $states _]"
return "
/*** Class that contains $contained ***/
class $classname {
public:
$contained item;
};
$classname ${classname}_var; /* global var */
template int cbv_container<$classname> ($classname arg);"
}
# Generate useful statements that use a class in the debugee program
proc generate_stmts { classprefix states {cbvfun "cbv"}} {
set classname "${classprefix}_[join $states _]"
# Having an explicit call to the cbv function in the debugee program
# ensures that the compiler will emit necessary function in the binary.
if {[is_copy_constructible $states]} {
set cbvcall "$cbvfun<$classname> (${classname}_var);\n"
} else {
set cbvcall ""
}
return "$cbvcall"
}
# Generate the complete debugee program
proc generate_program { classes stmts } {
global ADDED
return "
/*** THIS FILE IS GENERATED BY THE TEST. ***/
static int tracer = 0;
/* The call-by-value function. */
template <class T>
int
cbv (T arg)
{
arg.data\[0\] += $ADDED; // intentionally modify the arg
return arg.data\[0\];
}
template <class T>
int
cbv_container (T arg)
{
arg.item.data\[0\] += $ADDED; // intentionally modify
return arg.item.data\[0\];
}
$classes
int
main (void)
{
$stmts
/* stop here */
return 0;
}"
}
# Compute all the combinations of special function states.
# We do not contain the 'deleted' state for the destructor,
# because it is illegal to have stack-allocated objects
# whose destructor have been deleted. This case is covered
# in pass-by-ref-2 via heap-allocated objects.
set options_nodelete [list absent explicit defaultedIn defaultedOut]
set options [concat $options_nodelete {deleted}]
set all_combinations {}
foreach cctor $options {
foreach dtor $options_nodelete {
foreach mctor $options {
lappend all_combinations [list $cctor $dtor $mctor]
}
}
}
# Generate the classes.
set classes ""
set stmts ""
foreach state $all_combinations {
append classes [generate_small_class $state]
append stmts [generate_stmts "Small" $state]
append classes [generate_large_class $state]
append stmts [generate_stmts "Large" $state]
append classes [generate_derived_class $state]
append stmts [generate_stmts "Derived" $state]
append classes [generate_container_class $state]
append stmts [generate_stmts "Container" $state "cbv_container"]
}
# Generate the program code and compile
set program [generate_program $classes $stmts]
set srcfile [standard_output_file ${srcfile}]
gdb_produce_source $srcfile $program
set options {debug c++ additional_flags=-std=c++11}
if {[prepare_for_testing "failed to prepare" $testfile $srcfile $options]} {
return -1
}
if {![runto_main]} {
return -1
}
set bp_location [gdb_get_line_number "stop here"]
gdb_breakpoint $bp_location
gdb_continue_to_breakpoint "end of main" ".*return .*;"
# Do the checks for a given class whose name is prefixed with PREFIX,
# and whose special functions have the states given in STATES.
# The name of the call-by-value function and the expression to access
# the data field can be specified explicitly if the default values
# do not work.
proc test_for_class { prefix states cbvfun data_field length} {
set name "${prefix}_[join $states _]"
set cctor [lindex $states 0]
set dtor [lindex $states 1]
set mctor [lindex $states 2]
global ORIGINAL
global CUSTOM
global ADDED
global TRACE
# GCC version <= 6 and Clang do not emit DW_AT_defaulted and DW_AT_deleted.
set is_gcc_6_or_older [test_compiler_info {gcc-[0-6]-*}]
set is_clang [test_compiler_info {clang-*}]
# But Clang version >= 7 emits DW_AT_calling_convention for types.
set is_clang_6_or_older [test_compiler_info {clang-[0-6]-*}]
with_test_prefix $name {
if {[is_copy_constructible $states]} {
set expected [expr {$ORIGINAL + $ADDED}]
if {$cctor == "explicit"} {
set expected [expr {$CUSTOM + $ADDED}]
}
if {$dtor == "explicit"} {
gdb_test "print tracer = 0" " = 0" "reset the tracer"
}
if {$cctor == "defaultedIn" || $dtor == "defaultedIn"} {
if {$is_gcc_6_or_older || $is_clang_6_or_older} {
setup_xfail "*-*-*"
} elseif {$is_clang} {
# If this is a pass-by-value case, Clang >= 7's
# DW_AT_calling_convention leads to the right decision.
# Otherwise, it is expected to fail.
if {"defaultedOut" in $states || "explicit" in $states} {
setup_xfail "*-*-*"
}
}
}
gdb_test "print ${cbvfun}<$name> (${name}_var)" " = $expected" \
"call '$cbvfun'"
gdb_test "print ${name}_var.${data_field}\[0\]" " = $ORIGINAL" \
"cbv argument should not change (item 0)"
if {$length > 1} {
set last_index [expr $length - 1]
gdb_test "print ${name}_var.${data_field}\[$last_index\]" \
" = $ORIGINAL" \
"cbv argument should not change (item $last_index)"
}
if {$dtor == "explicit"} {
if {$cctor == "defaultedIn"
&& ($is_gcc_6_or_older || $is_clang)} {
setup_xfail "*-*-*"
}
gdb_test "print tracer" " = $TRACE" \
"destructor should be called"
}
} else {
if {$cctor == "deleted" && ($is_gcc_6_or_older || $is_clang)} {
setup_xfail "*-*-*"
}
gdb_test "print ${cbvfun}<$name> (${name}_var)" \
".* cannot be evaluated .* '${name}' is not copy constructible" \
"calling '$cbvfun' should be refused"
}
}
}
foreach state $all_combinations {
test_for_class "Small" $state "cbv" "data" $SMALL
test_for_class "Large" $state "cbv" "data" $LARGE
test_for_class "Derived" $state "cbv" "data" 1
test_for_class "Container" $state "cbv_container" "item.data" 1
}