Add support for compat mode

Build zlib-ng twice in order to distribute the compat sub-packages that
can fully replace zlib (zlib-ng-compat and zlib-ng-compat-devel).

Run ABI tests provided by upstream during %check.

Signed-off-by: Tulio Magno Quites Machado Filho <tuliom@redhat.com>

far.diff

@@ -0,0 +1,12 @@
+diff --git a/zconf.h.in b/zconf.h.in
+index 074f0255..e7183db3 100644
+--- a/zconf.h.in
++++ b/zconf.h.in
+@@ -200,4 +200,7 @@ typedef PTRDIFF_TYPE ptrdiff_t;
+ 
+ typedef size_t z_size_t;
+ 
++/* Some packages depend on FAR being defined, i.e. old versions of minizip. */
++#define FAR
++
+ #endif /* ZCONF_H */

zlib-ng.spec

@@ -1,18 +1,36 @@
+%bcond_without compat
+%bcond_without sanitizers
+
 # Be explicit about the soname in order to avoid unintentional changes.
+# Before modifying any of the sonames, this must be announced to the Fedora
+# community as it may break many other packages.
+# A change proposal is needed:
+# https://docs.fedoraproject.org/en-US/program_management/changes_policy/
 %global soname libz-ng.so.2
+%global compat_soname libz.so.1
+
+# Compatible with the following zlib version.
+%global zlib_ver 1.2.13
+# Obsoletes zlib versions less than.
+%global zlib_obsoletes 1.3
+
+# ABI files for ix86 and s390x are not available upstream.
+%global supported_abi_test aarch64 ppc64le x86_64
 
 Name:		zlib-ng
 Version:	2.1.3
-Release:	2%{?dist}
+Release:	7%{?dist}
 Summary:	Zlib replacement with optimizations
 License:	zlib
 Url:		https://github.com/zlib-ng/zlib-ng
 Source0:	https://github.com/zlib-ng/zlib-ng/archive/%{version}/%{name}-%{version}.tar.gz
 
-ExclusiveArch:	aarch64 i686 ppc64le s390x x86_64
+Patch:		far.diff
+
 BuildRequires:	cmake >= 3.1
 BuildRequires:	gcc-c++
 BuildRequires:	cmake(GTest)
+BuildRequires:	libabigail
 
 %description
 zlib-ng is a zlib replacement that provides optimizations for "next generation"
@@ -23,23 +41,128 @@ Summary:	Development files for %{name}
 Requires:	%{name}%{?_isa} = %{version}-%{release}
 
 %description	devel
-The %{name}-devel package contains static libraries and header files for
+The %{name}-devel package contains libraries and header files for developing
-developing application that use %{name}.
+application that use %{name}.
+
+%if %{with compat}
+
+%package	compat
+Summary:	Zlib implementation provided by %{name}
+Provides:	zlib = %{zlib_ver}
+Provides:	zlib%{?_isa} = %{zlib_ver}
+Conflicts:	zlib%{?_isa}
+Obsoletes:	zlib < %{zlib_obsoletes}
+
+%description	compat
+zlib-ng is a zlib replacement that provides optimizations for "next generation"
+systems.
+The %{name}-compat package contains the library that is API and binary
+compatible with zlib.
+
+%package	compat-devel
+Summary:	Development files for %{name}-compat
+Requires:	%{name}-compat%{?_isa} = %{version}-%{release}
+Provides:	zlib-devel = %{zlib_ver}
+Provides:	zlib-devel%{?_isa} = %{zlib_ver}
+Conflicts:	zlib-devel%{?_isa}
+Obsoletes:	zlib-devel < %{zlib_obsoletes}
+
+%description	compat-devel
+The %{name}-compat-devel package contains libraries and header files for
+developing application that use zlib.
+
+%endif
 
 %prep
 %autosetup -p1 -n %{name}-%{version}
 
 %build
+cat <<_EOF_
+###########################################################################
+#
+# Build the default zlib-ng library
+#
+###########################################################################
+_EOF_
+
 # zlib-ng uses a different macro for library directory.
-%cmake -DWITH_SANITIZERS=ON -DINSTALL_LIB_DIR=%{_libdir}
+%global cmake_param %{?with_sanitizers:-DWITH_SANITIZER=ON} -DINSTALL_LIB_DIR=%{_libdir}
+
+# Setting __cmake_builddir is not necessary in this step, but do it anyway for symmetry.
+%global __cmake_builddir %{_vpath_builddir}
+%cmake %{cmake_param}
 %cmake_build
 
+%if %{with compat}
+cat <<_EOF_
+###########################################################################
+#
+# Build the compat mode library
+#
+###########################################################################
+_EOF_
+
+%global __cmake_builddir %{_vpath_builddir}-compat
+# Disable new strategies in order to keep compatibility with zlib.
+%cmake %{cmake_param} -DZLIB_COMPAT=ON -DWITH_NEW_STRATEGIES=OFF
+%cmake_build
+%endif
+
 %check
+cat <<_EOF_
+###########################################################################
+#
+# Run the zlib-ng tests
+#
+###########################################################################
+_EOF_
+
+%global __cmake_builddir %{_vpath_builddir}
 %ctest
 
+%ifarch ppc64le
+# Workaround Copr, that sets _target_cpu to ppc64le.
+%global target_cpu powerpc64le
+%else
+%global target_cpu %{_target_cpu}
+%endif
+
+%ifarch x86_64
+%global vendor pc
+%else
+%global vendor unknown
+%endif
+
+%ifarch %{supported_abi_test}
+CHOST=%{target_cpu}-%{vendor}-linux-gnu sh test/abicheck.sh
+%endif
+
+%if %{with compat}
+cat <<_EOF_
+###########################################################################
+#
+# Run the compat mode tests
+#
+###########################################################################
+_EOF_
+
+%global __cmake_builddir %{_vpath_builddir}-compat
+%ctest
+%ifarch %{supported_abi_test}
+CHOST=%{target_cpu}-%{vendor}-linux-gnu sh test/abicheck.sh --zlib-compat
+%endif
+%endif
+
+
 %install
+%global __cmake_builddir %{_vpath_builddir}
 %cmake_install
 
+%if %{with compat}
+%global __cmake_builddir %{_vpath_builddir}-compat
+%cmake_install
+%endif
+
 %files
 %license LICENSE.md
 %doc README.md
@@ -53,7 +176,39 @@ developing application that use %{name}.
 %{_libdir}/libz-ng.so
 %{_libdir}/pkgconfig/%{name}.pc
 
+%if %{with compat}
+
+%files compat
+%{_libdir}/%{compat_soname}
+%{_libdir}/libz.so.%{zlib_ver}.zlib-ng
+
+%files compat-devel
+%{_includedir}/zconf.h
+%{_includedir}/zlib.h
+%{_includedir}/zlib_name_mangling.h
+%{_libdir}/libz.so
+%{_libdir}/pkgconfig/zlib.pc
+
+
+%endif
+
+
 %changelog
+* Wed Oct 18 2023 Tulio Magno Quites Machado Filho <tuliom@redhat.com> - 2.1.3-7
+- Improve the patch that defines the FAR macro
+
+* Wed Sep 27 2023 Tulio Magno Quites Machado Filho <tuliom@redhat.com> - 2.1.3-6
+- Add a patch that defines the FAR macro
+
+* Wed Sep 20 2023 Tulio Magno Quites Machado Filho <tuliom@redhat.com> - 2.1.3-5
+- Fix WITH_SANITIZER
+
+* Tue Sep 19 2023 Tulio Magno Quites Machado Filho <tuliom@redhat.com> - 2.1.3-4
+- Disable WITH_NEW_STRATEGIES in compat mode
+
+* Thu Aug 24 2023 Tulio Magno Quites Machado Filho <tuliom@redhat.com> - 2.1.3-3
+- Enable zlib compat build
+
 * Sat Jul 22 2023 Fedora Release Engineering <releng@fedoraproject.org> - 2.1.3-2
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild