Re: memory leak in the code?
On 9 Jan., 05:50, Grizlyk <grizl...@yandex.ru> wrote:
peter koch wrote:
I suspect, you are speaking about ideal situation,
where we do not use C-style arrays or C-style arrays
allocated in heap, because we are replacing them with
the help of appropreate wrappers, don't?
You use the standard elements available, e.g. std::string. This is
very good advice.
The good advice has no provements. Any simple thing is always better
than complex one. What is the problems with strXXX in the concrete
context? Nothing. The code in not intended to be reused, never.
What is wrong with the code is that you are using three lines of code
where one should suffice and that your code risks a buffer-overflow.
And this in a section of code, where performance of code matters
zilch.
Apart from that, my guess is that the std::string approach would be
faster than your homegrown code.
[snip]
So, we will see your opinion on the idea below.
but insists on using elements of a coding style
that were meant for more low-level programming.
It is freedom, to be without strange limitations :).
It is freedom being without limitations which obviously you don't seem
to have. You are just not using your freedom wisely, but what can one
expect from a russian? ;-)
"looks more like C"?
How will you express the following code
from the program with the help of C and why:
I am not going to spend my time determining
what your code is supposed to do, but a glimpse
shows that your code is basically C
Who is the grave "glimpse", that can not see templates, namespaces and
tons of C++ code :)? He is wrong.
A template and a namespace does not do it. Sorry.
The template is an attempt to have a "smart" pointer to some
storage perhaps?
The concrete listed template is intended to be storage for all dynamic
C-style arrays, that required inside of any block scope. The template
is owner of memory of the arrays and makes all that neccesery to
correctly return unused memory into system back.
Something that std::vector does perfectly.
The template has only free-stating methods, so implementation of the
template has not more overhead than ordinary POD pointer.
Should I interpret the above to mean that you believe that member
functions cause any overhead? Sorry - you are wrong again.
I am afraid I fail to see the purpose of that class.
This is very useful thing, if you need C-style array with unknown for
compile time size of the array, for non-intrusive, dynamic arrays
allocated by new[].
Again, std::vector does this just as well and just as efficiently.
This is not possible so far as I know.
strcpy is C and thus does not throw.
Did you write your own strcpy?
In the case of "strcpy", that will be comiled into
"rep movsl", what kind of replacement could be done
without lost of perfomance?
Did you measure your perceived loss?
Sorry, It was question for which I was going to answer myself: "what
kind of replacement _could_ be done...". No, i did not measure
anything, but saw assempler output.
So you measured nothing. Actually, I am not surprised.
A SIG is not a C++ exception.
I agree.
Do not transform hardware exceptions into C++ exceptions.
I guess, you advise to do not throw from signal handler, probably? I
agree. To deliver SIGxxx to signal handler environment of executable
do some thing, that outside of C++ scope, but not prohibited by C++ to
catch excepion inside of strcpy.
At any rate, is does not matter, who can throw inside of strcpy, but
the code is ready to catch the possible exception and return the
unused memory into system back.
The details with delete/delete[] look like
variable without type.
The point is that new[] is a "low-level" detail, practically never
needed in a C++ program.
All depends from target, but if "new[]" is not prohibited, it must
work correctly. I hope, that for C++ "correct work" will be selected
instead of attacks again "new[]".
New works perfectly and is not prohibited, there's just no use for it.
For example, just because C-arrays are not prohibited.
But speaking seriously, we sometimes need low-level
dinamic buffers for simple DTA and so on,
with special behaviour, so we can write wrappers
(other than vector<>) and use raw memory management.
I do not know what DTA is
DTA is a raw memory area for transfer data over any boundaries or used
for temporary storage.
std::vector is perfect for "DTA".
but if you can use operator new you can also
use std::vector.
But i am not goint do use no one member of class vector<>, and the
vector<> will only protect the memory from me, but i need the memory
raw accessed.
Which you can get.
1. C++ was designed to do not insist on any concrete way of
programming. If you say, that the way is poor, you must say what
conrete thing is a problem with the way. The fact of existance of
other ways is not enough.
You did show that yourself, I believe having three errors in a 20
lines of code because you refused to use the standard library and
insisted on using lower level tools that you did not understand.
And what _exactly_ i do not understand in the concrete low level
tools? I see, you want to say, that all errors in C++ produced only by
human, in spite of compiler bring all forces to help him?
And your advice looks like you believe, that if i want to use any part
of C++, but i am not sure do i understand or do not what i am going to
do, i must select the standard library, doesn't it? Or what?
My advice is to use the standard library. If the standard library does
not do what you want fast enough (and if you are sure you understand
the standard library and use it correctly), you can try to roll wour
own specialisation and see it it helps.
The question was: are you allowing use of other parts of language, and
if yes, why they can not be done also safe, as your lovely standard
library - is only true way to the future?
Use safe features first. A program is worth nothing it does not work
correctly and using unsafe constructs is one way to spend time testing
rather than developing.
2. C++ was designed to be set of orthogonal,
self-independed parts of solid language, that means,
that you can select and use any set of parts you wish.
If you say, that the part of language must be used
here, you must say what conrete thing is a problem
without. The fact of existance of other parts
is not enough.
You can express multiplication by using addition
and a for loop, but doing so would be silly.
I do not understand, i did not use "addition and for loop". What is
concrete problem in my example without unused parts (excluding errors
already detected by me).
With C++ you have a nice toolbox, but to me it seems you're only using
the hammer. This is not an efficient way to program.
3. Library ( he was speaking about io implementation )
is _not_ a part of C++ language. And it is right,
because there are many libraries in
the world.
I am not sure I understand you here, but the C++ standard
library is very much a part of the C++ language.
All is quite clear. Type "int" is a part of language, but function
"printf" is not. The "printf" is member of a ordinary library, but the
library is standard, so you can think, that the library will exist and
your code will be portable and understandable for other readers.
That is wrong. printf (to use a bad example) is part of the C++
standard library.
/Peter