what is the difference between the two command?

[Ian Lance Taylor]

On Sun, Jan 20, 2013 at 5:01 PM, horseriver <horserivers at gmail.com> wrote:
> On Sun, Jan 20, 2013 at 09:07:15AM -0800, Ian Lance Taylor wrote:
>> On Sat, Jan 19, 2013 at 1:30 PM, horseriver <horserivers at gmail.com> wrote:
>> > On Sat, Jan 19, 2013 at 09:47:53PM -0800, Ian Lance Taylor wrote:
>> >> On Fri, Jan 18, 2013 at 10:19 PM, horseriver <horserivers at gmail.com> wrote:
>> >> > hi:
>> >> >
>> >> >    Here are two command for producting one .so file :
>> >> >
>> >> >    1. gcc  -nostdlib -Wl,-T,vsyscall.lds vsyscall-int80.o -o vsyscall-int80.so
>> >> >
>> >> >    2. ld  -T vsyscall.lds vsyscall-int80.o -o vsyscall-int80.so
>> >>
>> >> There is no substantive difference between these commands.  There are
>> >> various minor differences that probably don't matter.  Use the -v
>> >> option when invoking gcc to see precisely how it invokes the linker.
>> >>
>> >> In particular, invoking the linker via the gcc driver will cause some
>> >> C++-specific operations to occur when needed, but since you aren't
>> >> using C++ in this case they won't happen.
>> >
>> > Thanks!
>> >
>> >    I have a weird problem here!
>> >
>> >    When I type the 1  to make vsyscall-int80.so ,ld report error: Not enough room for program headers, try linking with -N
>> >
>> >    But,When I type 2  to make vsyscall-int80.so,it works successfully.
>> >
>> >     What is the reason?
>>
>> I don't know.  Run the complete gcc command with the -v option and you
>> will see precisely how it invokes the linker.
>
>    gcc -v
> Using built-in specs.
> Target: i486-linux-gnu
> Configured with: ../src/configure -v --with-pkgversion='Debian 4.4.5-8' --with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.4 --enable-shared --enable-multiarch --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-targets=all --with-arch-32=i586 --with-tune=generic --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
> Thread model: posix
>
> which option make the two commands different?

You are just showing the results of gcc -v.  I'm asking you to add -v
to the actual gcc command that you are running.  That is: gcc
-nostdlib -Wl,-T,vsyscall.lds vsyscall-int80.o -o vsyscall-int80.so
-v.

Ian