This document describes how libexpat was packaged for build2. In particular,
this understanding will be useful when upgrading to a new upstream version.
See ../README-DEV for general notes on Expat packaging.

Symlink the required upstream files:

$ ln -s ../COPYING
$ pushd libexpat
$ ln -s ../../upstream/expat/lib/{*.{c,h},libexpat.def} ./
$ ln -s ../../upstream/expat/expat_config.h.cmake expat_config.h.cmake.orig
$ popd

Use some of the upstream's tests for testing:

$ pushd unit-tests/regression/
$ ln -s ../../../upstream/expat/tests/*.{c,h} ./
$ popd

Create libexpat/expat_config.h using as a base the upstream's auto-generated
header, winconfig.h, and/or configure.ac.

Re-creating libexpat/expat_config.h from scratch every time we upgrade to a
new upstream version would be a pain. Instead we can only (un)define the newly
introduced macros, comparing the already defined and currently used macro
sets. Note that we can use this approach to also deduce the initial set of
macros running the above commands for the upstream's auto-generated
expat_config.h:

$ ln -s ../../upstream/expat/expat_config.h.cmake libexpat/expat_config.h.cmake.orig

$ for m in `cat libexpat/expat_config.h.cmake.orig libexpat/winconfig.h | \
            sed -n 's/.*#\s*\(define\|cmakedefine\)\s\{1,\}\([_a-zA-Z0-9]\{1,\}\)\(\s.*\)\{0,1\}$/\2/p' | sort -u`; do
    if grep -q -e "\b$m\b" `find -L . -type f -not -path "./tests/*" -a \( -name '*.h' -a ! -name expat_config.h -o -name '*.c' \)`; then
      echo "$m"
    fi
  done >used-macros

$ cat libexpat/expat_config.h | \
  sed -n 's/^#\s*\(define\|undef\)\s\{1,\}\([_a-z_A-Z0-9]\{1,\}\)\(\s.*\)\{0,1\}$/\2/p' | \
  sort -u >defined-macros

$ diff defined-macros used-macros | grep '<' >remove-macros
$ diff defined-macros used-macros | grep '>' >add-macros