CODEWITHSUNDEEP
gcclinkerdefaultlibraries
edouard.gilles
edouard.gilles

Reputation: 31

GNU GCC/LD : Which libraries are linked by default?

I am a regular C programmer, and there's something I have wondered for some time about GNU GCC/LD internals.

I have noticed that, when passing a sequence of object files to GCC (e.g gcc main.o otherfile.o), GCC automatically links libc.a library file without my explicitly specifying -lc in the options. Similarly, when I compile a program using ncurses, I just need to specify -lncurses and libtinfo.a gets linked automatically (no need to specify -ltinfo). In other words, even though ncurses functions use functions from libtinfo (for instance, unctrl()), I don't need to explicitly link libtinfo.

How can it be possible?

Does GCC/LD have a list of "default libraries" where it looks for missing symbols when linking? If such a table exists, where is it and how can it be configured?

Upvotes: 2

Views: 1896

Answers (1)

Jonathan Leffler
Jonathan Leffler

Reputation: 753665

A direct answer is that you can see what libraries are linked by command line options by adding -v to the linking command line. This will show you the commands as they are executed.

The C library and the GCC support library or libraries are linked automatically; other libraries have to be specified manually.

The case of -lncurses and libtinfo.a (libtinfo.so?) is rather different. There, the link command used to build libncurses.so tells the linker that this library also needs -ltinfo, so it automatically picks up the extra library.

Upvotes: 2

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