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Re: Design decisions

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On 06/23/12 09:03 PM, jacob navia wrote:
> Le 23/06/12 02:59, Ian Collins a écrit :
>> On 06/23/12 12:13 PM, jacob navia wrote:
>
>>> Yes. Up to 30% or more of space are now taken by tables describing the
>>> stack movements to the unwinding virtual machine that the C++ run time
>>> needs.
>>
>> Now where did you dig up that "fact" from?  Automatic destruction works
>> perfectly well without run time support.
>
> Confirmed. Most C++ programmers have no idea of what is needed behind
> the scene to make all those nice syntax constructs work.

Confirmed, you are talking out of the wrong end again.

> AUTOMATIC DESTRUCTION MUST WORK IN THE CASE OF A THROW.

Not if you turn exceptions off, which is a better comparison in this 
case (C++ as a better C).  I use C++ (mainly to get automatic resource 
management) in driver and kernel module code where there isn't any run 
time support, so I most certainly do know what goes on behind the scenes.

For example, the following

extern "C" int* get();
extern "C" void done(int*);
extern "C" void process(int*);

struct Manage {
   int* n;
   Manage( int* n ) : n(n) {}
   ~Manage() {done(n);}
};

void f() {
   int* n = get();
   Manage m(n);
   process(n);
}

Compiles (with g++ -S -O3 -fno-exceptions) to:

	.file	"z.cc"
	.text
	.p2align 4,,15
.globl _Z1fv
	.type	_Z1fv, @function
_Z1fv:
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%ebx
	subl	$20, %esp
	call	get
	movl	%eax, %ebx
	movl	%eax, (%esp)
	call	process
	movl	%ebx, (%esp)
	call	done
	addl	$20, %esp
	popl	%ebx
	popl	%ebp
	ret
	.size	_Z1fv, .-_Z1fv
	.ident	"GCC: (GNU) 4.5.2"

Which is probably tighter than any manual stack pushing and popping.

-- 
Ian Collins

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Design decisions jacob navia <jacob@spamsink.net> - 2012-06-21 22:19 +0200
  Re: Design decisions Andrew Cooper <amc96@cam.ac.uk> - 2012-06-21 21:43 +0100
  Re: Design decisions "BartC" <bc@freeuk.com> - 2012-06-21 22:02 +0100
    Re: Design decisions Gareth Owen <gwowen@gmail.com> - 2012-06-21 23:23 +0100
      Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-22 09:12 +0200
        Re: Design decisions Ian Collins <ian-news@hotmail.com> - 2012-06-22 19:44 +1200
          Re: Design decisions "Joe." <antelope3@news.net> - 2012-06-25 00:32 -0600
        Re: Design decisions gwowen <gwowen@gmail.com> - 2012-06-22 01:00 -0700
          Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-22 10:08 +0200
            Re: Design decisions Gareth Owen <gwowen@gmail.com> - 2012-06-22 17:18 +0100
              Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-22 18:27 +0200
                Re: Design decisions Ian Collins <ian-news@hotmail.com> - 2012-06-23 08:44 +1200
                Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-22 23:58 +0200
                Re: Design decisions Ian Collins <ian-news@hotmail.com> - 2012-06-23 10:21 +1200
                Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-23 02:13 +0200
                Re: Design decisions Ian Collins <ian-news@hotmail.com> - 2012-06-23 12:59 +1200
                Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-23 11:03 +0200
                Re: Design decisions Ian Collins <ian-news@hotmail.com> - 2012-06-23 21:52 +1200
                Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-23 12:32 +0200
                Re: Design decisions Gareth Owen <gwowen@gmail.com> - 2012-06-23 13:54 +0100
            Re: Design decisions "Joe." <antelope3@news.net> - 2012-06-25 00:36 -0600
          Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-22 10:42 +0200
            Re: Design decisions Gareth Owen <gwowen@gmail.com> - 2012-06-22 17:18 +0100
            Re: Design decisions jacob navia <jacob@spamsink.net> - 2012-06-24 18:32 +0200
    Re: Design decisions James Kuyper <jameskuyper@verizon.net> - 2012-06-21 18:43 -0400
      Re: Design decisions "Joe." <antelope3@news.net> - 2012-06-25 00:40 -0600
    Re: Design decisions "Joe." <antelope3@news.net> - 2012-06-25 00:28 -0600
  Re: Design decisions "io_x" <a@b.c.invalid> - 2012-06-22 08:35 +0200
  Re: Design decisions Neil Cerutti <neilc@norwich.edu> - 2012-06-22 12:40 +0000
    Re: Design decisions gwowen <gwowen@gmail.com> - 2012-06-22 06:01 -0700
      Re: Design decisions Neil Cerutti <neilc@norwich.edu> - 2012-06-22 14:26 +0000
    Re: Design decisions Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-06-22 14:01 +0100
    Re: Design decisions David Resnick <lndresnick@gmail.com> - 2012-06-22 06:13 -0700
  Re: Design decisions Jens Gustedt <jens.gustedt@loria.fr> - 2012-06-22 19:05 +0200
  Re: Design decisions "Joe." <antelope3@news.net> - 2012-06-25 00:27 -0600

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