Re: pkg-config wisdom

[Bob Friesenhahn]

On Fri, 23 Oct 2009, John Calcote wrote:
> If your project uses libxml's API, then you as the maintainer should be very 
> aware of requisite dependencies of that library. The AC_CHECK_LIB macro 
> accepts a fifth argument, other-libraries, which is a whitespace-separated 
> list of dependent libraries (actually command-line options, e.g., [-lzlib 
> -lpthread -lX11]) that are required by the primary library that you're 
> checking for. Note, however, that if you've already tested for the presence 
> of any of these 2nd and 3rd level libraries in previous AC_CHECK_LIB tests, 
> then these references will already be in the LIBS variable, and thus used in 
> this test automatically.

Unfortunately, the libraries used by the library being tested may be 
only optionally used and assuming that the library is used may result 
in an uneeded library being added to the build.  There may be an 
option of using several other libraries (e.g. an XML library like 
libxml2 or expat) to perform a function and it is easy to guess wrong 
if both option libraries happen to be on the system.

In this case life would be better if all libraries had a ".la" file 
and if Autoconf used libtool type functionality (e.g. consult the .la 
files) as part of its testing.

> I don't know of any flavor of Unix that has "interlibrary dependencies" as 
> you describe them here - at least most people don't use those linker options. 
> Additionally, most people on this list are not necessarily pro-Linux, and 
> anti-Solaris/BSD/MacOSX/AIX, and so on. The Autotools attempts to be 
> Unix-flavor agnostic, which is one of the strengths of these tools.

The Linux linker does seem to automatically inject library 
dependencies, which tends to paper over any configuration problems.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/