Date: Mon, 21 Apr 2008 06:01:07 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: ertr1013@student.uu.se Cc: emily.bckr@gmail.com, freebsd-hackers@freebsd.org Subject: Re: symbol table Message-ID: <20080421.060107.1079619394.imp@bsdimp.com> In-Reply-To: <20080421070050.GA13685@owl.midgard.homeip.net> References: <20080420103910.GA92852@owl.midgard.homeip.net> <20080420.232432.-1175574853.imp@bsdimp.com> <20080421070050.GA13685@owl.midgard.homeip.net>
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In message: <20080421070050.GA13685@owl.midgard.homeip.net> Erik Trulsson <ertr1013@student.uu.se> writes: : On Sun, Apr 20, 2008 at 11:24:32PM -0600, M. Warner Losh wrote: : > In message: <20080420103910.GA92852@owl.midgard.homeip.net> : > Erik Trulsson <ertr1013@student.uu.se> writes: : > : On Sun, Apr 20, 2008 at 12:02:09PM +0300, emily becker wrote: : > : > Hi, : > : > : > : > I have a question about symbol table. : > : > One of the section In symbol table is memory adress which symbol is located. : > : > I wonder if this memory adress is bound at run-time or compile-time? : > : : > : It depends. Symbols referring to objects in a dynamically loaded library : > : will be bound at run-time, the rest should be bound at compile-time. : > : > They are bound at link-time, not compile-time. This is splitting a : > fine hair, but compile-time is when a .o or .so is created, while link : > time combines .o-like things together into a bigger thing. : : Well, I consider linking to be part of the compilation process so for : me link-time is a subset of compile-time. : You are however completely correct that it is at link-time that the binding : happens (for those symbols that can be resolved at link-time anyway.) While you might consider them the same, these are very important differences that need to be taken into account. A compile-time constant, for example, can be used to size an automatic array. A link-time or run-time constant cannot without gcc's extensions (magic tricks can be played to make link-time constants size certain global objects, but then sizeof() those objects fail). The terminology is well worn, and matters in some contexts, so I tend to be a stickler here... Warner
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