Date: Tue, 24 Nov 1998 16:30:49 -0800 (PST) From: John Polstra <jdp@polstra.com> To: Joel Ray Holveck <joelh@gnu.org> Cc: current@FreeBSD.ORG Subject: Re: Elf linker question. Message-ID: <XFMail.981124163049.jdp@polstra.com> In-Reply-To: <86d86cy7do.fsf@detlev.UUCP>
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On 24-Nov-98 Joel Ray Holveck wrote:
>> No, you're exactly right. But lazy binding applies only to function
>> calls. There are also data references that have to be relocated.
>> Those can't be done lazily.
>
> How are things like:
> sighander_t mysig = libsig;
> handled?
Any time you take the address of a function, the linker actually fills
in the address of a little stub routine. It's the same stub that
gets called when you call an external function. The first time it is
executed, the stub jumps to code in the dynamic linker that does the
lazy binding to whatever function is being called. Then it rewires
itself (an indirect jump is used) so that all future calls will go
straight to the target function.
I'm glossing over some details. But anyway, you get the address of
the stub, not the address of the actual function.
John
---
John Polstra jdp@polstra.com
John D. Polstra & Co., Inc. Seattle, Washington USA
"Nobody ever went broke underestimating the taste of the American public."
-- H. L. Mencken
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