[Gm2] A bit more informed

[Martin Kalbfuß]

I tested some command lines and had a look at the results with "file"
and "ldd". Nice tools.

I created a shared object out of a relocatable with

gm2 -fPIC -c Library1.mod
gm2 -shared Library1.mod -o libtest.so

file gives me

Library1.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV),
not stripped

for the module and

libtest.so: ELF 32-bit LSB shared object, Intel 80386, version 1 (SYSV),
dynamically linked, not stripped

for libtest.so

So this looks fine.

Then I compiled the program object file with

gm2 -c program.mod

file gives me

program.o: ELF 32-bit LSB relocatable, Intel 80386, version 1 (SYSV),
not stripped

Looks like this is a relocatable, too. But I didn't used -fPIC?

Then I linked the program with

gm2 program.mod -L. -ltest

file gives me

a.out: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV),
dynamically linked (uses shared libs), for GNU/Linux 2.6.18, not
stripped

and ldd

linux-gate.so.1 =>  (0xb805e000)
libtest.so => /home/martin/opt/projects/mod/libtest.so (0xb8031000)
libm.so.6 => /lib/i686/cmov/libm.so.6 (0xb800b000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0xb7f19000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0xb7eee000)
libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb7d8f000)
/lib/ld-linux.so.2 (0xb805f000)

All looks fine. And the program executes without any errors.

I'm still confused about the relocatables in the SO directory of pim
library. How this works? Is the shared object created on the fly? Or can
I link directly to relocatables?

What is -fshared good for?
Why do you used -fPIC -fshared for the creation of the shared object?
Why to use -fPIC if the object is a relocatable anyway?

I hope this looks a bit less lazy then the entry before.