[ icewm-Bugs-3469478 ] Improve implementation of constructors

Bugs item #3469478, was opened at 2012-01-04 09:18
Message generated for change (Comment added) made by elfring
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Category: icewm-1.3
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Markus Elfring (elfring)
Assigned to: Nobody/Anonymous (nobody)
Summary: Improve implementation of constructors

Initial Comment:
I have noticed that some assignments are used in the constructor bodies.

Examples:
http://icewm.cvs.sourceforge.net/viewvc/icewm/icewm-1.2/src/ywindow.cc?revision=1.54&view=markup
http://icewm.cvs.sourceforge.net/viewvc/icewm/icewm-1.2/src/yapp.cc?revision=1.59&view=markup
http://icewm.cvs.sourceforge.net/viewvc/icewm/icewm-1.2/src/ytimer.cc?revision=1.2&view=markup

The recommended way for performing efficient construction is to use the initialisation list.
http://dietmar-kuehl.de/mirror/c++-faq/ctors.html#faq-10.6
http://cprogramming.com/tutorial/initialization-lists-c++.html
http://www.codeguru.com/cpp/tic/tic0145.shtml
http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=15&rl=1
http://goingware.com/tips/parameters/membervars.html

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>Comment By: Markus Elfring (elfring)
Date: 2012-01-08 04:30

Message:
If you do not want to support exception handling, you do not need to change
the mentioned source code places because the compiler parameter
"-fno-exceptions" should have got the effect that your program will be
eventually aborted.
http://gcc.gnu.org/onlinedocs/libstdc++/manual/using_exceptions.html#intro.using.exception.no

But I hope that you are interested to improve your software a bit more.

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Comment By: Eduard Bloch (thefirstone)
Date: 2012-01-08 03:37

Message:
PS: double-thinking about it, I guess the problem can be "solved" by
replacing the normal new/delete operators with non-throwing versions, see
http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=40 for
example (just the other way round).

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Comment By: Eduard Bloch (thefirstone)
Date: 2012-01-06 16:52

Message:
@elfring: I suggest that you start your problem description with telling
what the actual problem  is ("here: new throws std::bad_alloc") and not
with throwing buzzwords and imprecise RTFM hints at people. No offense
implied.

@Marko: unfortunately, he has a point. std::bad_alloc is thrown by the
libstdcxx's implementation of malloc so using -fno-exceptions does not
really help. On Debian, I link with libsupc++ but even that one throws
std::bad_alloc (for some reason I assumed the opposite).

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Comment By: Markus Elfring (elfring)
Date: 2012-01-05 11:44

Message:
Would you like to support exception handling?
Would you like to avoid any difficulties from an event like the exception
"std::bad_alloc" that might occur during execution of affected constructor
bodies?

http://stackoverflow.com/questions/7575459/c-should-i-initialize-pointer-members-that-are-assigned-to-in-the-constructor
http://stackoverflow.com/questions/563221/is-there-an-implicit-default-constructor-in-c#answer-4982720

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Comment By: Eduard Bloch (thefirstone)
Date: 2012-01-05 11:01

Message:
I don't know what Marko thinks, here is my opinion:

Using C++11 features just for the sake of code beautification is not worth
it.

If you can safe time or enhance code safety (or both) then we might talk
about it, but in this case, what's the point? Those member variables are
private and only allocated on heap in order to keep the stack size sane,
and they are never passed around. The only good reason for auto_ptr (and
family) might be the work around exception handling in constructors... but
icewm does not use exceptions so that point is void.


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Comment By: Markus Elfring (elfring)
Date: 2012-01-05 05:30

Message:
Would you also like to consider any adjustments for the initialisation of
pointer member variables?

Update candidates:
- fMotion = new XMotionEvent;
- fDocked = new YXEmbedClient(this, this, win);
- cpu = new int *[taskBarCPUSamples];
- fUpdateTimer = new YTimer(taskBarCPUDelay);
- clockTimer = new YTimer(1000);
- ppp_in = new long[taskBarNetSamples];
- ppp_out = new long[taskBarNetSamples];
- fUpdateTimer = new YTimer();
- tray = new SysTray();
- fClientContainer = new YClientContainer(this, this);
- fTitleBar = new YFrameTitleBar(this, this);
- Other constructors: TextView, HTextView, IceSame, AboutDlg,
CtrlAltDelete

How do you think about to reuse the class "std::unique_ptr"?
http://en.wikipedia.org/wiki/Smart_pointer#C.2B.2B_Smart_Pointers

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Comment By: Eduard Bloch (thefirstone)
Date: 2012-01-05 03:53

Message:
In theory, you are right.

In practice... seriously, WTF? Every normal C++ compiler from the last
decade should be able to optimize trivial assignment lists as needed.

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