From: Glynn Clements <glynn.clements@virgin.net>
To: "Theo. Sean Schulze" <tschulze@teamfinders.org>
Cc: linux-c-programming@vger.kernel.org
Subject: Re: undefined sqrt()
Date: Fri, 25 Oct 2002 09:17:07 +0100 [thread overview]
Message-ID: <15800.65027.133218.947339@cerise.nosuchdomain.co.uk> (raw)
In-Reply-To: <20021024205042.GA3766@teamfinders.org>
Theo. Sean Schulze wrote:
> Thanks. The "-lm" did it. Why? I see from the gcc man page that the
> "-l" is a linker option. Am I right that the linker then searches for
> "libm.a"?
To be precise, it will normally look for libm.so (shared library)
first (unless the -static switch was used), then look for libm.a.
> Again, why, if I am right, would it need to after I included
> math.h? Isn't sqrt() in math.h?
The declaration is in math.h, but a declaration simply tells the
compiler that the function exists, along with the number and types of
its arguments and its return type.
In order to produce a working program, you have to provide the actual
code which implements that function. In the case of sqrt(), the code
is in libm.
For functions which are in libc, you don't have to provide any -l
switches, as gcc (when used for linking) automatically instructs the
compiler to link against libc.
--
Glynn Clements <glynn.clements@virgin.net>
next prev parent reply other threads:[~2002-10-25 8:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-24 20:06 undefined sqrt() Theo. Sean Schulze
2002-10-24 20:17 ` Karthik Vishwanath
2002-10-24 20:50 ` Theo. Sean Schulze
2002-10-24 21:50 ` Karthik Vishwanath
2002-10-25 8:17 ` Glynn Clements [this message]
2002-10-25 17:27 ` Theo. Sean Schulze
2002-10-25 19:29 ` Glynn Clements
2002-10-24 20:28 ` Steven Smith
-- strict thread matches above, loose matches on Subject: below --
2002-10-26 10:07 Ruslan U. Zakirov
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