finite() in ANSI C?

[Nicholas R. Markham]

When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
implicit declaration of function 'finite'. Does this mean that finite() is
not part of ANSI C, or that I didn't include a necessary header file? (I
did include math.h.) Either way, is there a recommended way to check if a
float or double is finite in ANSI C? Thanks.

[Joona I Palaste]

Nicholas R. Markham <ma*******@bigf oot.com> scribbled the following:

When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
implicit declaration of function 'finite'. Does this mean that finite() is
not part of ANSI C, or that I didn't include a necessary header file? (I
did include math.h.) Either way, is there a recommended way to check if a
float or double is finite in ANSI C? Thanks.

finite() is not part of ANSI C.

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"'So called' means: 'There is a long explanation for this, but I have no
time to explain it here.'"
- JIPsoft

[Brian Gough]

"Nicholas R. Markham" <ma*******@bigf oot.com> writes:

When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
implicit declaration of function 'finite'. Does this mean that finite() is
not part of ANSI C, or that I didn't include a necessary header file? (I
did include math.h.) Either way, is there a recommended way to check if a
float or double is finite in ANSI C? Thanks.

finite() is from BSD. The equivalent in C99 is isfinite().

--
Brian Gough

Network Theory Ltd,
Publishing Free Software Manuals --- http://www.network-theory.co.uk/

[Martin Ambuhl]

Nicholas R. Markham wrote:

When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
implicit declaration of function 'finite'. Does this mean that finite() is
not part of ANSI C, or that I didn't include a necessary header file? (I
did include math.h.) Either way, is there a recommended way to check if a
float or double is finite in ANSI C? Thanks.

The headers (in particular <math.h>) in your implementation will show
some things which are in C99 but not in C89 hidden within #ifdefs
designed to make them invisible with C89. Just move them outside the
#ifdefs. This does not solve the problem of things missing completely
from the headers (and perhaps from the libraries).

[Dan Pop]

In <cb***********@ newsfeeds.rpi.e du> "Nicholas R. Markham" <ma*******@bigf oot.com> writes:

When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
implicit declaration of function 'finite'. Does this mean that finite() is
not part of ANSI C, or that I didn't include a necessary header file? (I
did include math.h.) Either way, is there a recommended way to check if a
float or double is finite in ANSI C? Thanks.

C89 provides no support for the IEEE-754 gadgets and the effect of -ansi
is to remove all the extensions declared in the standard headers.

C99 does provide support for all the IEEE-754 stuff, but the name of the
thing is isfinite and it is a macro (defined in math.h). If your math.h
has it, you may have to enable it using the -std=c99 option:

fangorn:~/tmp 30> cat test.c
#include <math.h>

int main()
{
return !isfinite(1);
}
fangorn:~/tmp 31> gcc test.c
/tmp/ccwzl0tE.o(.tex t+0x18): In function `main':
: undefined reference to `isfinite'
collect2: ld returned 1 exit status
fangorn:~/tmp 32> gcc -std=c99 test.c
fangorn:~/tmp 33> ./a.out
fangorn:~/tmp 34> echo $status
0

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Nicholas R. Markham]

"Brian Gough" <bj*@network-theory.co.uk> wrote in message
news:87******** ****@network-theory.co.uk...

"Nicholas R. Markham" <ma*******@bigf oot.com> writes:

When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
implicit declaration of function 'finite'. Does this mean that finite() is not part of ANSI C, or that I didn't include a necessary header file? (I did include math.h.) Either way, is there a recommended way to check if a float or double is finite in ANSI C? Thanks.

finite() is from BSD. The equivalent in C99 is isfinite().

So since finite() is not part of any standard, I probably shouldn't be using
it. But:

- isfinite() is in C99 but not C89; it's an improvement, but wouldn't I be
better off to stick with C89, to maximize portability?

- when I try to use isfinite() on a Solaris machine with gcc 3.3, including
the math.h header, linking with the math library and specifying -std=c99, I
still get an implicit declaration warning. Shouldn't that work?

[Dan Pop]

In <cb**********@n ewsfeeds.rpi.ed u> "Nicholas R. Markham" <ma*******@bigf oot.com> writes:

"Brian Gough" <bj*@network-theory.co.uk> wrote in message
news:87******* *****@network-theory.co.uk...

"Nicholas R. Markham" <ma*******@bigf oot.com> writes:

> When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
> implicit declaration of function 'finite'. Does this mean that finite()is > not part of ANSI C, or that I didn't include a necessary header file?(I > did include math.h.) Either way, is there a recommended way to check ifa > float or double is finite in ANSI C? Thanks.
finite() is from BSD. The equivalent in C99 is isfinite().

So since finite() is not part of any standard, I probably shouldn't be using
it. But:

- isfinite() is in C99 but not C89; it's an improvement, but wouldn't I be
better off to stick with C89, to maximize portability?

In which case, there is NO way to test whether a value is finite or not.
Portable C code cannot even assume the existence of Inf's.
- when I try to use isfinite() on a Solaris machine with gcc 3.3, including
the math.h header, linking with the math library and specifying -std=c99, I
still get an implicit declaration warning. Shouldn't that work?

Keep in mind that gcc is only a compiler. If the headers and libraries
provided by Solaris do not claim full C99 support, you have no good
reason to expect isfinite() to be available.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Irrwahn Grausewitz]

"Nicholas R. Markham" <ma*******@bigf oot.com> wrote:

"Brian Gough" <bj*@network-theory.co.uk> wrote:

"Nicholas R. Markham" <ma*******@bigf oot.com> writes:

> When I compile with the -ansi option (using gcc 3.2.3) I'm warned of an
> implicit declaration of function 'finite'.

<snip> finite() is from BSD. The equivalent in C99 is isfinite().
So since finite() is not part of any standard, I probably shouldn't be using
it. But:

- isfinite() is in C99 but not C89; it's an improvement, but wouldn't I be
better off to stick with C89, to maximize portability?

It would. But you have to provide your own implementation of
isfinite, of course.
- when I try to use isfinite() on a Solaris machine with gcc 3.3, including
the math.h header, linking with the math library and specifying -std=c99, I
still get an implicit declaration warning. Shouldn't that work?

Smells like a broken (read: incomplete) library implementation.
<OT> It works correctly with the mingw port of gcc 3.3.1. </OT>

Regards
--
Irrwahn Grausewitz (ir*******@free net.de)
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[Martin Ambuhl]

Nicholas R. Markham wrote:

So since finite() is not part of any standard, I probably shouldn't be using
it. But:

- isfinite() is in C99 but not C89; it's an improvement, but wouldn't I be
better off to stick with C89, to maximize portability?

- when I try to use isfinite() on a Solaris machine with gcc 3.3, including
the math.h header, linking with the math library and specifying -std=c99, I
still get an implicit declaration warning. Shouldn't that work?

Please read my earlier post <2j************ *@uni-berlin.de>

[Dan Pop]

In <3v************ *************** *****@4ax.com> Irrwahn Grausewitz <ir*******@free net.de> writes:

Smells like a broken (read: incomplete) library implementation.
Merely like an implementation that doesn't claim C99 conformance.
<OT> It works correctly with the mingw port of gcc 3.3.1. </OT>

I doubt that the mingw port of gcc 3.3.1 comes with conforming C99
libraries. So, your example is not only off topic, but also irrelevant.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de