Re: [Mingw-users] how to use ld.exe

[Tatsh <dd...@gm...>]

Mark Allyn wrote:
> Hi Keith and Greg -
> 
> Yes, I know that the sensible thing to do is to simply do gcc proggy.o -o
> proggy.exe.   But, I am one of those silly people who enjoy doing things
>  the hard way so that I learn new stuff.

If you are curious, `man ld`. It has everything you could need to know.

> 
> I really would like to know what the runtime start up code is. I used the
>  -v option in the "standard" gcc -g proggy.c command but the output is very
>  difficult to read.
> 
> You don't want to squelch curiousity do you?  Even old geezers like me
> should have the opportunity to learn new things, wouldn't you think?  It
> seems to me that the only damage I'm doing is wasting some of my own time
> and a couple billion or so electrons...if you decide to not waste your own
> time replying.
> 
> Anyway, thanks, and regards as well,
> 
> Mark
> 
> 
> ----- Original Message -----
> From: "Keith Marshall" <kei...@us...>
> To: <min...@li...>
> Sent: Monday, May 10, 2010 5:26 PM
> Subject: Re: [Mingw-users] how to use ld.exe
> 
> > On Monday 10 May 2010 22:05:30 Mark Allyn wrote:
> >> Please forgive a newbie question regarding ld usage.
> >> I thought for fun I would compile a c program using:
> >>
> >> gcc -c -g proggy.c -o proggy.o
> >
> > So far, so good.
> >
> >> And I did.  I got proggy.o
> >
> > As we would expect.
> >
> >> Then I decided to do a link like this:
> >>
> >> ld -L/c/mingw/lib proggy.o -lmsvcrt
> >
> > Now you are just trying to be too clever for your own good; the more
> > so since you claim to be a newbie, you should not even think about
> > invoking ld directly -- you should use gcc to link, like this:
> >
> >  gcc -o proggy.exe proggy.o
> >
> > and leave gcc to pass the proper flags and prerequisite system object
> > modules and libraries.
> >
> >> But, I get back a message indicating that:
> >> _main  and __alloca are undefined references.  Other crt symbols
> >> like pow() and printf() resolved just fine.
> >
> > Those which are unresolved would be provided by the runtime start-up
> > code, which you've not asked ld to include in the link.
> >
> >> If I go back to the c code and change main into _main, and
> >> recompile, the linker works just fine.
> >
> > Now you've substituted your own _main for the proper start-up code,
> > (which would ultimately call your main); your application almost
> > certainly will not initialise correctly.
> >
> >> So....what is going on here?  What do I have to put into the ld
> >> command line to get the linker to understand that my "main" symbol
> >> is OK?  Do I have to set an option in the initial GCC command, or
> >> do I have to put a library into the LD step?
> >
> > Neither; just use GCC to link, as is intended.
> >
> >
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Tatsh
www.tatsh.net
dd...@gm...