eli-schwartz
commented
11 months ago @michaelrsweet I've kept it in tree and checked that running autoconf -f without any other autotools programs works, and as far as I can tell the license issue is not a problem due to the special exception. Hopefully this means it's okay to use.
michaelrsweet
PKG_CHECK_MODULES is battle tested and provides some convenient functionality such as standardizing on $PKG_CONFIG instead of $PKGCONFIG, marking various additional variables as precious, and upating the
./configure --helptext to notify you which variables can be used to control the configure checks.It's also shorter and simpler from the perspective of configure.ac (and the added complexity in pkg.m4 is someone else's maintenance burden).
Note: pkg.m4 is GPL-2-or-later licensed. The GPL 2 is incompatible with pdfio's Apache license. There are two reasons why this is still okay:
The "or-later" clause means we can include pkg.m4 under the terms of the GPL-3, if we wish. This is the same license that autoconf itself uses, and is compatible with the Apache license.
Like autoconf itself, pkg.m4 has a special clause permitting its distribution, when included "as part of a program that contains a configuration script generated by Autoconf", under whatever terms the rest of the program uses. Since that is what we are doing here, this means that pkg.m4 is licensed under the Apache license as long as it is used as part of the pdfio ./configure build system.