(void) printf vs printf

[whatluo]

Hi, c.l.cs

I noticed that someone like add (void) before the printf call,
like: (void) printf("Timeout \n"); while the others does't. So
can someone tell me whether there any gains in adding
(void) to printf.

Thanks,

Whatluo.

[Walter Roberson]

In article <11************ **********@g44g 2000cwa.googleg roups.com>,
whatluo <wh*****@gmail. com> wrote:

I noticed that someone like add (void) before the printf call,
like: (void) printf("Timeout \n"); while the others does't. So
can someone tell me whether there any gains in adding
(void) to printf.

It can silence a compiler (or stand-alone "lint" program) warning
that the result of a function has been thrown away.

Also, if the programmer is being particularily careful to check
error conditions at every place errors can occur, then
a (void) on the printf() can be a signal that the lack of error
checking on that one statement is a deliberate design decision
instead of something that was overlooked.
--
History is a pile of debris -- Laurie Anderson

[Christian Bau]

In article <11************ **********@g44g 2000cwa.googleg roups.com>,
"whatluo" <wh*****@gmail. com> wrote:

Hi, c.l.cs

I noticed that someone like add (void) before the printf call,
like: (void) printf("Timeout \n"); while the others does't. So
can someone tell me whether there any gains in adding
(void) to printf.

printf returns a value.

When a function returns a value, and the programmer ignores the code, I
would want to know why. There are usually two explanations: The
programmer made a mistake ignoring the return value, or the programmer
did ignore the return value on purpose. When you write

printf (...);

I have no idea if you wanted to ignore the return value or not. If you
write

(void) printf (...);

it tells me that the programmer knew that printf returns a value, and
made a conscious decision to ignore that value. Do some professional
programming, try finding a few bugs in a million lines of other people's
code, and you will appreciate such things.

[SM Ryan]

Christian Bau <ch***********@ cbau.freeserve. co.uk> wrote:
# In article <11************ **********@g44g 2000cwa.googleg roups.com>,
# "whatluo" <wh*****@gmail. com> wrote:
#
# > Hi, c.l.cs
# >
# > I noticed that someone like add (void) before the printf call,
# > like: (void) printf("Timeout \n"); while the others does't. So
# > can someone tell me whether there any gains in adding
# > (void) to printf.
#
# printf returns a value.
#
# When a function returns a value, and the programmer ignores the code, I
# would want to know why. There are usually two explanations: The
# programmer made a mistake ignoring the return value, or the programmer
# did ignore the return value on purpose. When you write

I routinely notice lots of people checking the return of printf
instead of simply looking at the terminal window.

--
SM Ryan http://www.rawbw.com/~wyrmwif/
Leave it to the Catholics to destroy existence.

[Giorgos Keramidas]

SM Ryan <wy*****@tang o-sierra-oscar-foxtrot-tango.fake.org> writes:

Christian Bau <ch***********@ cbau.freeserve. co.uk> wrote:
# In article <11************ **********@g44g 2000cwa.googleg roups.com>,
# "whatluo" <wh*****@gmail. com> wrote:
#
# > Hi, c.l.cs
# >
# > I noticed that someone like add (void) before the printf call,
# > like: (void) printf("Timeout \n"); while the others does't. So
# > can someone tell me whether there any gains in adding
# > (void) to printf.
#
# printf returns a value.
#
# When a function returns a value, and the programmer ignores the code, I
# would want to know why. There are usually two explanations: The
# programmer made a mistake ignoring the return value, or the programmer
# did ignore the return value on purpose. When you write

I routinely notice lots of people checking the return of printf
instead of simply looking at the terminal window.

Of course, sometimes just staring at terminals may be deceptive at
times. Consider a program that prints whitespace separated words and
shows two words on your terminal:

hello world

Have these been printed by a single call to printf?

printf("hello world\n");

Two successive calls?

printf("hello ");
printf("world\n ");

Or maybe three calls, where the middle one failed, for some obscure
(and undetected by just staring at the output) reason?

printf("hello ");
printf("strange ");
printf("world\n ");

[Richard Bos]

"whatluo" <wh*****@gmail. com> wrote:

I noticed that someone like add (void) before the printf call,
like: (void) printf("Timeout \n"); while the others does't. So
can someone tell me whether there any gains in adding
(void) to printf.

Nothing. It shuts up geriatric versions of lint, that's all. But you're
better off using a lint that wasn't designed on clay tablets anyway.

Richard

[Richard Bos]

"P.J. Plauger" <pj*@dinkumware .com> wrote:

Note, however, that these rules do *not* apply to casting
the value returned by malloc. So, despite the fact(s) that

-- a (void) cast is *never* needed in a conforming C program, and

-- it's only real-world effect is to silence diagnostics in
a non-standard dialect of C (lint)

it is nevertheless a Good Thing (TM) to write (void) casts and
a Bad Thing (SM) to do exactly the same thing for the return
value of malloc.
No, because of those reasons, and more, it is a Bad Thing to write
(void) casts and also a Bad Thing to cast malloc().
Go figure.

Furrfu.

Richard

[Bhatnagar Achindra]

int printf(...) and void printf(...)

When we use printf(...) and we don't handle the return values the
return value is destroyed with the loading and execution of the next
statement call.

When use void printf(...) we instruct the system to flush out any
return values before moving to the next statement, thus we clean up any
possibility of fetching the return value.

Positive values from the function call specifies the number of bytes
written to STDOUT, excluding '\0' in general, while a negative value
tells the error code if occured.

[No Such Luck]

> Also, if the programmer is being particularily careful to check

error conditions at every place errors can occur, then
a (void) on the printf() can be a signal that the lack of error
checking on that one statement is a deliberate design decision
instead of something that was overlooked.

Interesting. I knew things like successful file openings should be
error checked, and pointers should be checked before accessing, etc.
But printfs? What is usually the accepted degree of error checking?

[Eric Sosman]

No Such Luck wrote:

Also, if the programmer is being particularily careful to check
error conditions at every place errors can occur, then
a (void) on the printf() can be a signal that the lack of error
checking on that one statement is a deliberate design decision
instead of something that was overlooked.

Interesting. I knew things like successful file openings should be
error checked, and pointers should be checked before accessing, etc.
But printfs? What is usually the accepted degree of error checking?

How important is the output? What are the consequences
if it fails to appear?

<whimsy>

A complete absence of error checking suggests that the
programmer places no value on the output and doesn't care
whether it appears or not. If so, the program's efficiency
can probably be improved by removing all the printf() calls,
along with the computations that produce data for them.
Following this principle, here is an optimized version of
the canonical "Hello, world!" program:

int main(void) {
return 0;
}

A great many programs can be optimized this way, and it
turns out that quite a few of them, after optimization,
become identical to the code shown above. This is a great
savings, because debugging and testing this one piece of
code essentially debugs and tests all those other programs
at the same time. A triumph for code re-use!

</whimsy>

--
Er*********@sun .com