depends_lib, depends_build, depends_run, oh my

[Kevin Van Vechten]

On Aug 6, 2007, at 10:07 AM, markd at macports.org wrote:

>> Why do we have depends_lib, depends_build and depends_run? Why not
>> just a single "depends"? Why does it matter which phase requires the
>> other software? Isn't it enough to know that the other software is
>> required at some point, and so MacPorts should install that other
>> software first?

Depends_build dependencies are only needed if you're actually  
building the software.  They're not needed at all once the software  
is built and installed.  (Think of gcc).

Depends_run dependencies are needed when the software is run, but not  
necessarily to build the software.  (Think of a program that does a  
fork/exec of /usr/bin/foo at runtime).

Depends_lib dependencies are needed both at build time (for headers  
and libraries to link against) and at run time (to provide necessary  
code).

For binary packages, you'd only need to consider depends_lib +  
depends_run.  Even for those building their own software, it makes  
sense to distinguish since it gives a better sense of what uninstalls  
might break (i.e. gcc is a depends_build for most projects, but  
uninstalling it wouldn't interfere with many ports operation).

- kvv