When making a library on unix, is anything but "ar rcs" necessary?

Question

I have a number of source files I want to agglomerate into a .a file. I make the library with the command

ar rcs libcathat.a thing1.o thing2.o fish.o

I then attempt to link to this library with the same compiler I used to make the .o files (g++):

 g++ -L/path/to/cathat -lcathat seuss.o -o seuss

But this produces errors when I try to use functions defined in thing1.cpp (and in theory represented in thing.o) of the form:

/path/seuss.cpp:46: undefined reference to `redFishBlueFish(int, char**)'

Is there something else I need to do to a .a file to make it possible to link to it?

Answer 1

Try moving the linker statements to the end:

g++ seuss.o -o seuss -L/path/to/cathat -lcathat

If that doesn't work, make sure those symbols are actually in the archive:

nm libcathat.a