testsuite/gdb.cp/pass-by-ref.exp

# Copyright 2007-2023 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"
    return
}

# 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
}