How to do that all depends on the compiler and/or IDE you are using. Basically, a library is nothing more than a collection of compiled functions that are in a file with *.lib or *.a file name. *nix computers also have something called shared libraries, which has a *.so file name.

Edited 4 Years Ago by Ancient Dragon: n/a

WaltP has challenged me on this, with his reputation comment.

I stand by my original line. I can take a C source file, compile it into an object, and I'm done - that object file is then a library. A standard *.a file is no more than a bunch of these object files stuck together; a single object file is perfectly usable as a library.

Comments
I agree

So there is some interpretation there. Sure, an object file can be compiled into an executable but it cant be 'linked' to in the traditional sense without converting it to a .a archive. (I'm talking purely Linux here as I am less familiar with how Windows handles this)

So an object file isn't technically a library even though it can be compiled into an executable in certain contexts.

@Ancient Dragon: I'm curious how you do this.

On Linux I get the following:

# Compiling object file directly into binary
$ gcc -c t1.c
$ gcc t2.c t1.o

# Trying to link to .o file
$ gcc -c t1.c -L. -lt1.o
/usr/bin/ld: cannot find -lt1.o
collect2: ld returned 1 exit status

$ cp t1.o libt1.o
$ gcc -c t1.c -L. -lt1
/usr/bin/ld: cannot find -lt1
collect2: ld returned 1 exit status

# Create the static library
$ ar -cvq libt1.a t1.o
$ gcc -c t1.c -L. -lt1

Is there another way I am not considering?

Is there another way I am not considering?

> gcc -c foo.c
> gcc -c bar.c
> gcc -o baz foo.o bar.o
>

Of course an object file can be linked. In fact, only the object files are linked.

A library is a convenient way to package a collection of objects. They are not linked directly. The linker extracts required objects from the library and links them.

Edited 4 Years Ago by nezachem: n/a

Is there another way I am not considering?

The gcc call does an awful lot for you when you ask it to take care of the linking. Here's the longhand linker call:

gcc -c func.c
gcc -c main.c

and now calling the linker...
/usr/bin/ld --build-id --eh-frame-hdr -m elf_x86_64 --hash-style=both -dynamic-linker /lib64/ld-linux-x86-64.so.2 -z relro /usr/lib/gcc/x86_64-linux-gnu/4.4.3/../../../../lib/crt1.o /usr/lib/gcc/x86_64-linux-gnu/4.4.3/../../../../lib/crti.o /usr/lib/gcc/x86_64-linux-gnu/4.4.3/crtbegin.o -L/usr/lib/gcc/x86_64-linux-gnu/4.4.3 -L/usr/lib/gcc/x86_64-linux-gnu/4.4.3 -L/usr/lib/gcc/x86_64-linux-gnu/4.4.3/../../../../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/4.4.3/../../.. -L/usr/lib/x86_64-linux-gnu -v main.o func.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc/x86_64-linux-gnu/4.4.3/crtend.o /usr/lib/gcc/x86_64-linux-gnu/4.4.3/../../../../lib/crtn.o


The -l option for the linker tells the linker that the file specified is an ar format.

Edited 4 Years Ago by Moschops: n/a

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