是否为新的子程序调用或新的@_重用了@_元素？

Question

我想这取决于背景.

1. 它在&func呼叫时被重用
2. 它是为所有其他呼叫创建的

我有这个代码,我eval在第1004行遇到意外的电话:

sub save_context {
    @DB::context =  ( \@_, (caller 2)[8..10], $@, $_ );  # line 1004
    print_state "\nTRAPPED IN  ", "\n\n"   if _ddd;
    DB::state( 'inDB', 1 );
}

这个堆栈跟踪:

DB /x/local/lib/perl5/Devel/DebugHooks.pm 1419 DB::orig_frames 
DB /x/local/lib/perl5/Devel/DebugHooks.pm 1460 DB::push_frame 
DB /x/local/lib/perl5/Devel/DebugHooks.pm 1004 DB::__ANON__[/x/local/lib/perl5/Devel/DebugHooks.pm:1460] 
DB /x/local/lib/perl5/Devel/DebugHooks.pm 1004 (eval) 
DB /x/local/lib/perl5/Devel/DebugHooks.pm 1251 DB::save_context 
DB /x/local/lib/perl5/Devel/DebugHooks.pm 1288 DB::DB_my 1
MyApp::Controller::User /x/lib/MyApp/Controller/User.pm 41 DB::DB 1
Mojolicious /x/local/lib/perl5/Mojolicious.pm 133 MyApp::Controller::User::list 
Mojolicious::Plugins /x/local/lib/perl5/Mojolicious/Plugins.pm 15 Mojolicious::__ANON__[/x/local/lib/perl5/Mojolicious.pm:133] 
...

从我的日志文件中我可以看到DBIx::Class::DESTROYsub被调用:

DB::sub  DB::state: l:1 d:0 s:5 t:0  /x/local/lib/perl5/Devel/DebugHooks.pm:1004  -->  DBIx::Class::DESTROY

为什么对象破坏被推迟？我想这与@_某种方式有关

任何建议都赞赏这可能会触发对象破坏

Answer 1

在&func没有参数列表的调用中,不仅@_重用元素,还重用了整个元素@_.

sub main {
    print "main: @_ is ", \@_, "\n";
    func(@_);  # Values from @_ are copied into new @_. @_ after call: 1 2 3
    &func;     # Origin @_ is passed down.           So @_ after call: 2 3
}

sub func {
    print "func: @_ is ", \@_, "\n";
    shift @_;  # Here @_ is modified. Pay attention what values @_ left after call
}

main(1,2,3);  # @_ will be initialized by: 1 2 3

典型输出:

main: @_ is ARRAY(0xfc5958)
@_ initial: 1 2 3
func: @_ is ARRAY(0xfc5a00)
@_ after func(): 1 2 3
func: @_ is ARRAY(0xfc5958)
@_ after &func: 2 3

从去main到&func呼叫,@_没有本地化,复制或以任何方式改变.从呼叫中改变@_内部会影响呼叫者,但是不会从呼叫中改变呼叫.func&func@_func()