How do I prevent gcc from linking with GNU standard C library

How do I prevent gcc from linking with GNU standard C library

[Tanveer Ahmad]

Hi,
I want to link my program with a third party standard C library, instead of
the GNU standard C library. I used the "-nostdlib" option in gcc, however I
get the following warning during linking:

	/usr/bin/ld: warning: cannot find entry symbol _start; defaulting to
080488d0

and, when I run "ldd" on the this binary, I still see that it requires
libc.so.6

Here's my gcc command line :
gcc -D__STDC_VERSION__=199901L -g -c t1.c -I /test/include
gcc -D__STDC_VERSION__=199901L  -fhonor-std  -fno-builtin -o  a.out t1.o
-lpthread -lgcc -nostdlib -nodefaultlibs /test/lib/sxlgcc2.a

Please advice.

thanks,
--Tanveer.

Re: How do I prevent gcc from linking with GNU standard C library

[Daniel Jacobowitz]

On Fri, Apr 26, 2002 at 04:47:02PM -0700, Tanveer Ahmad wrote:
> Hi,
> I want to link my program with a third party standard C library, instead of
> the GNU standard C library. I used the "-nostdlib" option in gcc, however I
> get the following warning during linking:
> 
> 	/usr/bin/ld: warning: cannot find entry symbol _start; defaulting to
> 080488d0
> 
> and, when I run "ldd" on the this binary, I still see that it requires
> libc.so.6
> 
> Here's my gcc command line :
> gcc -D__STDC_VERSION__=199901L -g -c t1.c -I /test/include
> gcc -D__STDC_VERSION__=199901L  -fhonor-std  -fno-builtin -o  a.out t1.o
> -lpthread -lgcc -nostdlib -nodefaultlibs /test/lib/sxlgcc2.a
> 
> Please advice.

libpthread.so presumably relies on the GNU standard library.  You'll
need a copy from your third party library vendor.

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer

Re: How do I prevent gcc from linking with GNU standard C library

[Jim Wilson]

>I want to link my program with a third party standard C library, instead of
>the GNU standard C library. I used the "-nostdlib" option in gcc, however I
>get the following warning during linking:
>	/usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 080488d0

-nostdlib does two things.  It disables linking against the default libraries
(i.e. libgcc and libc), and it disables linking against the startup files
(i.e. crt0.o).  _start is defined in one of the startup files.  Your program
will not work without the startup files.

If your third party library includes startup files, you could try linking
against them.  Probably, however, the right solution is to stop using
-nostdlib.  This is really only useful for embedded systems.  You are
already using -nodefaultlibs, which will avoid linking in the standard C
library.

See the documentation for -nostartfiles, -nostdlib, and -nodefaultlibs.

Jim

Re: How do I prevent gcc from linking with GNU standard C library

[Roger Sayle]

> Here's my gcc command line :
> gcc -D__STDC_VERSION__=199901L -g -c t1.c -I /test/include
> gcc -D__STDC_VERSION__=199901L  -fhonor-std  -fno-builtin -o  a.out t1.o
> -lpthread -lgcc -nostdlib -nodefaultlibs /test/lib/sxlgcc2.a

Probably unrelated to your problem, but -fno-builtin is a compile
time flag, not a link time flag.  In your example above, it should
be specified in the first gcc invocation not the second.  I guess
you'll also need -I- to disable the standard include paths, rather
than just use -I to append /test/include to the list.

Roger
--
Roger Sayle,                         E-mail: roger@eyesopen.com
OpenEye Scientific Software,         WWW: http://www.eyesopen.com/
Suite 1107, 3600 Cerrillos Road,     Tel: (+1) 505-473-7385
Santa Fe, New Mexico, 87507.         Fax: (+1) 505-473-0833