Re: archives and header files

[pkurpis at keck dot hawaii dot edu (Peter Kurpis)]

> How do I know what C library file or archive needs to be specified
> when compiling C programs (with gcc)?  For example, if I want the
> math library and I use the math.h header file, I need to use the
> "-lm" option in the command line for the compiler.  What are the
> names (like "m" for math) for the other header file and archives to
> use in the "-l" option?  Is there a list somewhere?
> 
> I've been looking through the GLIBC manual / GCC manual and I don't
> see the answer. The manuals tell you which library in terms of
> header files but not which archive contains the functions.

 -lsomething  looks for  libsomething.a  or  libsomething.so  in ld's 
search path during linking.  This search path is somewhat system dependent, 
but there are usually three sources for the search path: 

	+  -L  options on the gcc command line
	+ a config file or built-in paths for ld
	+ environment variables (e.g. LD_LIBRARY_PATH).

I think for Standard C programs, the standard functions are defined
in libc and libm.  libc contains some additional "traditional" unix
stuff; libm is the math lib.

> A related question is: how can I find which functions are
> defined in any given archive (library) file (to approach the
> problem from the other direction)?

ldd libc.so
dump -t libc.a

See the man pages for other options.  You might need to  grep  out the
info you need.