About libraries.

g4j31a5 · 12-12-2006, 12:11 AM

Hi, I just wanted to ask questions about library. What's the difference of .so, .la, .a ? How do I know what a binary is linked against? Thanks.

paulsm4 · 12-12-2006, 12:33 AM

Hi -

.a files are "static libraries. You create them with "ar"; the binary code from these files is linked directly into your executable.

.so files are "shared libraries". You create them with "ld"; the executable merely contains a reference to the binary objects in the shared library. The library code itse;f isn't loaded until runtime, making the executable both smaller, and more flexible.

Both .a and .so libraries are very common: they're both used in just about every executable you'll build.

.la files, on the other hand, with the Gnu "libtool" package. They are somewhat less commonly used. You can read more about "libtool" - and the differences between .a, .so and .la files - here:

http://developer.gnome.org/doc/books...libraries.html

'Hope that helps .. PSM

g4j31a5 · 12-14-2006, 08:56 PM

Thanks, btw how do I know what library a binary is linked against? I tried to develop with SDL, but I didn't know if it was the libSDL.a or libSDL.so that was linked to my binary. I made it from KDevelop's wizard.

jschiwal · 12-14-2006, 09:16 PM

You can use the ldd command to list the dynamic libraries a program uses:

Code:

 ldd tar
        librt.so.1 => /lib64/librt.so.1 (0x00002b1d59c18000)
        libc.so.6 => /lib64/libc.so.6 (0x00002b1d59d21000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b1d59f51000)
        /lib64/ld-linux-x86-64.so.2 (0x00002b1d59afb000)

Of course, since you have the source code, you can read it as well.

g4j31a5 · 12-15-2006, 12:50 AM

Thanks. Yeah, maybe I can actually read it from the source code. But I don't know how. Still not familiar with Linux.