Why We Use C Than C++...

**EventHelix.com** · Jan 12 '06, 11:35 AM

Re: Why We Use C Than C++...

In a well developed C++ program, there isn't much difference between C
and C++ performance.

The following articles describe a mapping from C++ to C code.

http://www.eventhelix.com/RealtimeMantra/basics/ComparingCPPAndCPerformance.htm

http://www.eventhelix.com/RealtimeMantra/basics/ComparingCPPAndCPerformance2.htm

The biggest performance hit in C++ comes from the implicit passing of
the "this" pointer in every
function. However, C++ more than makes up for this by better locality
of reference. This translates
to improved cache performance.

--
EventStudio System Designer 2.5 - http://www.EventHelix.com/EventStudio
System Design with Sequence Diagrams in PDF and Word EMF

**Richard Heathfield** · Jan 12 '06, 03:15 PM

Re: Why We Use C Than C++...

sonugeetha@gmai l.com said:
[color=blue]
> Hi, Please help me in this regard...
> All the kernel level programs are written in C... (i.e: Open Source
> LINUX)... Why are they not using C++... I personally feel that C++ is
> more easy to code than C... When i searched in our encyclopedia (i.e
> Google), i came up with several answers, telling "C is much faster than
> C++ and most kernal prgms uses only C" ... But why is it so...? Why
> they use C for these OS based programs.. Please Help me with detailed
> explanation...[/color]

Partly because C is faster (in places). Partly because it's simpler, so it's
easier to get right. But mostly, I think, because C came first. When the
kernel was first being written, C had already firmed up, whilst C++ was
still in a state of considerable flux. And, once it's /written/ in C, if a
reasonable job was made (which certainly seems to be the case), why on
earth would anyone bother to rewrite it?

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999

http://www.cpax.org.uk

email: rjh at above domain (but drop the www, obviously)

**Dag-Erling Smørgrav** · Jan 12 '06, 04:05 PM

Re: Why We Use C Than C++...

Richard Heathfield <invalid@invali d.invalid> writes:[color=blue]
> Partly because C is faster (in places). Partly because it's simpler,
> so it's easier to get right. But mostly, I think, because C came
> first.[/color]

Another important factor is that C++ requires more run-time support
code to work properly.

DES
--
Dag-Erling Smørgrav - des@des.no

**Walter Roberson** · Jan 12 '06, 05:15 PM

Re: Why We Use C Than C++...

In article <1137065013.641 067.148570@f14g 2000cwb.googleg roups.com>,
EventHelix.com <eventhelix@gma il.com> wrote:[color=blue]
>In a well developed C++ program, there isn't much difference between C
>and C++ performance.[/color]
[color=blue]
>The following articles describe a mapping from C++ to C code.[/color]
[color=blue]
>http://www.eventhelix.com/RealtimeMa...erformance.htm
>http://www.eventhelix.com/RealtimeMa...rformance2.htm[/color]

I just read through those two articles. They are short on details,
make a lot of assumptions about -how- one programs in C; and the
conclusions are a bit of hand-waving not justified by the work that
has gone before.

In particular, I would say that the "Locality of Reference" conclusion
is based upon implementation factors rather than on language design,
and that the reasoning of that section appears faulty to me.
--
"It is important to remember that when it comes to law, computers
never make copies, only human beings make copies. Computers are given
commands, not permission. Only people can be given permission."
-- Brad Templeton

**Walter Roberson** · Jan 12 '06, 05:15 PM

Re: Why We Use C Than C++...

In article <86ace1sayk.fsf @xps.des.no>,
=?iso-8859-1?q?Dag-Erling_Sm=F8rgr av?= <des@des.no> wrote:[color=blue]
>Richard Heathfield <invalid@invali d.invalid> writes:[color=green]
>> Partly because C is faster (in places). Partly because it's simpler,
>> so it's easier to get right. But mostly, I think, because C came
>> first.[/color][/color]
[color=blue]
>Another important factor is that C++ requires more run-time support
>code to work properly.[/color]

The C++ Standard Library is many times as big as the C Standard Library,
And if one is reading through the C++ standard, it can be quite
difficult to figure out what the tradeoffs are between using the
several different approaches to any one task that are offered by
the C++ Standard Library.
--
Is there any thing whereof it may be said, See, this is new? It hath
been already of old time, which was before us. -- Ecclesiastes

**Walter Roberson** · Jan 12 '06, 05:25 PM

Re: Why We Use C Than C++...

In article <1137064443.960 141.168050@g49g 2000cwa.googleg roups.com>,
sonugeetha@gmai l.com <sonugeetha@gma il.com> wrote:[color=blue]
>All the kernel level programs are written in C... (i.e: Open Source
>LINUX)... Why are they not using C++...[/color]

If I understand correctly, there has been work on C++ for the Linux kernel.
For example,

http://netlab.ru.is/exception/LinuxCXX.shtml

According to the Linux FAQ, C++ is not generally well received for
the kernel, for a variety of reasons. The FAQ includes a quotation from
Linus from 2004:

In fact, in Linux we did try C++ once already, back in 1992.

It sucks. Trust me - writing kernel code in C++ is a BLOODY STUPID IDEA.

The fact is, C++ compilers are not trustworthy. They were even worse
in 1992, but some fundamental facts haven't changed:
o the whole C++ exception handling thing is fundamentally broken.
It's _especially_ broken for kernels.
o any compiler or language that likes to hide things like memory
allocations behind your back just isn't a good choice for a kernel.
o you can write object-oriented code (useful for filesystems etc) in C,
_without_ the crap that is C++.

In general, I'd say that anybody who designs his kernel modules for C++
is either
o (a) looking for problems
o (b) a C++ bigot that can't see what he is writing is really just C
anyway
o (c) was given an assignment in CS class to do so.
Feel free to make up (d).
--
Programming is what happens while you're busy making other plans.

**henryk.mueller@gmx.de** · Jan 12 '06, 05:35 PM

Re: Why We Use C Than C++...

> Another important factor is that C++ requires more run-time support[color=blue]
> code to work properly.[/color]

Nope.

The objective of C++ is that you do not pay for features you do not
use.

C++ is not faster or slower than C if you DO the same.

For example: C functions have no parameter "this". But static C++
function do not have a "this" parameter either.

So, compare only apples with apples....

I use C++ in an embedded environment. Mostly because of it's better
code encapsulation. You can write small and lean wrappers for
interfaces that actually contain mostly inline functions. So you have
no overhead but you can protect the user of your class from using it in
an unwanted way much better than in C, i.e. forget to call init in C
vs. do the init within the constructor.

There are a lot examples of C++ features that are done at compile time
and have no effect at runtime. They all help you to write more robust
code. Reference objects vs. pointers, const methods, const return
values and all this stuff...

The are only 3 reasons to use C over C++:
- you have no decent C++ compiler for your platform
- you have to continue a C project
- you are not allowed to use C++ because your boss still believes that
C++ is SLOW

Greets

Henryk

**Andrew Poelstra** · Jan 12 '06, 06:05 PM

Re: Why We Use C Than C++...

sonugeetha@gmai l.com wrote:[color=blue]
> Hi, Please help me in this regard...
> All the kernel level programs are written in C... (i.e: Open Source
> LINUX)... Why are they not using C++... I personally feel that C++ is
> more easy to code than C... When i searched in our encyclopedia (i.e
> Google), i came up with several answers, telling "C is much faster than
> C++ and most kernal prgms uses only C" ... But why is it so...? Why
> they use C for these OS based programs.. Please Help me with detailed
> explanation...
>
> Cheers,
> Balaji Jayaraman...[/color]

As has been mentioned, C hides a lot of memory allocations and stuff
from the user-programmer; obviously, you don't want that happening in a
kernel.

What I think is a far more annoying problem is the fact that
interfacing C++ is Assembler is hard, because C++ mangles the funtion
names to handle overriding properly. There are more details in 'PC
Assembly Language' by Dr. Paul Carter.

When doing kernels, you'll likely be interfacing with lots of low-level
ASM functions to handle hardware interrupts and what not; C is the most
portable language (across different compilers) for doing this.

**Flash Gordon** · Jan 12 '06, 06:15 PM

Re: Why We Use C Than C++...

Walter Roberson wrote:[color=blue]
> In article <1137065013.641 067.148570@f14g 2000cwb.googleg roups.com>,
> EventHelix.com <eventhelix@gma il.com> wrote:[color=green]
>> In a well developed C++ program, there isn't much difference between C
>> and C++ performance.[/color]
>[color=green]
>> The following articles describe a mapping from C++ to C code.[/color]
>[color=green]
>> http://www.eventhelix.com/RealtimeMa...erformance.htm
>> http://www.eventhelix.com/RealtimeMa...rformance2.htm[/color]
>
> I just read through those two articles. They are short on details,
> make a lot of assumptions about -how- one programs in C; and the
> conclusions are a bit of hand-waving not justified by the work that
> has gone before.
>
> In particular, I would say that the "Locality of Reference" conclusion
> is based upon implementation factors rather than on language design,
> and that the reasoning of that section appears faulty to me.[/color]

In addition, the articles are either a long way out of data (over 15
years) or the author does not really know C as it has been since it was
standardised. I say this because it is including malloc.h instead of the
standard header stdlib.h. Whichever is the case, it casts even further
doubt on whether the author is qualified to compare the languages.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

**James S. Singleton** · Jan 12 '06, 06:45 PM

Re: Why We Use C Than C++...

On Thu, 12 Jan 2006 03:14:04 -0800, sonugeetha@gmai l.com wrote:
[color=blue]
> Hi, Please help me in this regard...
> All the kernel level programs are written in C... (i.e: Open Source
> LINUX)... Why are they not using C++... I personally feel that C++ is more
> easy to code than C... When i searched in our encyclopedia (i.e Google), i
> came up with several answers, telling "C is much faster than C++ and most
> kernal prgms uses only C" ... But why is it so...? Why they use C for
> these OS based programs.. Please Help me with detailed explanation...[/color]

Another reason that no one has pointed out yet: Because object orient
design is not the silver bullet that many want to believe, and because
object orient design is something that comes naturally to many programmers
(good and bad) but doesn't to just as many (also good and bad).

**jacob navia** · Jan 12 '06, 07:25 PM

Re: Why We Use C Than C++...

James S. Singleton a écrit :[color=blue]
>
> Another reason that no one has pointed out yet: Because object orient
> design is not the silver bullet that many want to believe, and because
> object orient design is something that comes naturally to many programmers
> (good and bad) but doesn't to just as many (also good and bad).
>[/color]

YES!

And I would add another one:

Complexity with more complexity until no one on earth,
(besides Bjarne maybe) is able to understand the whole
language.

Man years of toiling to build incredible fragile compilers
that are incompatible with each other because not one of
them shares the same bug set. Obviously.

I have watched Bjarne and his followers start with the idea of a
"better C" and get swallowed alive by the dragons of complexity.

Automatic destructors can be replaced easily with a
garbage collector, what simplifies the whole thing
quite a bit without adding more complexity and new
features to the language itself.

Templates are one approach to genericity but that can be
better handled with metaprogramming , i.e. compile
time functions.

jacob

**Keith Thompson** · Jan 12 '06, 07:55 PM

Re: Why We Use C Than C++...

henryk.mueller@ gmx.de writes:
[...][color=blue]
> The are only 3 reasons to use C over C++:
> - you have no decent C++ compiler for your platform
> - you have to continue a C project
> - you are not allowed to use C++ because your boss still believes that
> C++ is SLOW[/color]

- you happen to know C better than C++;
- you happen to *like* C better than C++;
....

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

**Keith Thompson** · Jan 12 '06, 08:05 PM

Re: Why We Use C Than C++...

jacob navia <jacob@jacob.re mcomp.fr> writes:
[...][color=blue]
> Automatic destructors can be replaced easily with a
> garbage collector, what simplifies the whole thing
> quite a bit without adding more complexity and new
> features to the language itself.[/color]

As I understand it, garbage collection only reclaims allocated memory;
destructors can perform any arbitrary cleanup actions (closing files,
for example).

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

**jacob navia** · Jan 12 '06, 08:25 PM

Re: Why We Use C Than C++...

Keith Thompson a écrit :[color=blue]
> jacob navia <jacob@jacob.re mcomp.fr> writes:
> [...]
>[color=green]
>>Automatic destructors can be replaced easily with a
>>garbage collector, what simplifies the whole thing
>>quite a bit without adding more complexity and new
>>features to the language itself.[/color]
>
>
> As I understand it, garbage collection only reclaims allocated memory;
> destructors can perform any arbitrary cleanup actions (closing files,
> for example).
>[/color]

True, you have to invoke the cleanup yourself.
This may be a lot of work, or not relevant, depending on your
application.

Using exception handling, it is easy to do automatic cleanups
using the __finally clause. The exception handling provided by
lcc-win32 is just the compiler side of the native one
provided by the Win32 system.

jacob-

Why We Use C Than C++...

Why We Use C Than C++...

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