Introduce a btparse_api_version note and use it in definine the SONAME.

Most linux distributions require a versioned SONAME for all libraries
in /usr/lib. This provides such an SONAME by defining the version in
Build.PL.

We also provide a symlink with unversioned name to make the linking of
binaries to the shared library transparent.

Arguably this should be defined in the C source of btparse, but since
the version is taken from the perl module, this alternative is maybe
more acceptable; it is certainly simpler than parsing another file in
Build.PL.

Gbp-Pq: Name 0001-Introduce-a-btparse_api_version-note-and-use-it-in-d.patch

2 files changed, 22 insertions, 5 deletions

diff --git a/Build.PL b/Build.PL
index 3ec4ef8..e3d7c08 100644
--- a/Build.PL
+++ b/Build.PL
@@ -103,6 +103,10 @@ else {
     $hdrdir =~ s!/[^/]+/?$!/include!
 }
 $builder->notes( 'btparse_version' => $version );
+#
+# this should be increased everytime there is a non-upward compatible
+# change the library ABI.
+$builder->notes( 'btparse_api_version' => 2 );
 $builder->notes( 'lib_path'        => $libdir );
 $builder->add_build_element('usrlib');
 $builder->install_path( 'usrlib'     => $libdir );
diff --git a/inc/MyBuilder.pm b/inc/MyBuilder.pm
index 8c6f6f9..2725565 100644
--- a/inc/MyBuilder.pm
+++ b/inc/MyBuilder.pm
@@ -15,7 +15,7 @@ use ExtUtils::Mkbootstrap;
 
 use File::Spec::Functions qw.catdir catfile.;
 use File::Path qw.mkpath.;
-use Cwd 'abs_path';
+use Cwd;
 
 my @EXTRA_FLAGS = ();
 my @BINARIES = qw(biblex bibparse dumpnames);
@@ -334,9 +334,14 @@ sub ACTION_create_library {
 
 
     my $libbuilder = $self->notes('libbuilder');
+    my $APIVERSION = $self->notes('btparse_api_version');
     my $LIBEXT = $libbuilder->{libext};
 
-    print STDERR "\n** Creating libbtparse$LIBEXT\n";
+    my $symlink_exists = eval { symlink("",""); 1 };
+
+    my $SONAME= $symlink_exists ? "libbtparse$LIBEXT.$APIVERSION" : "libbtparse$LIBEXT";
+
+    print STDERR "\n** Creating $SONAME\n";
 
     my @modules = qw:init input bibtex err scan error
                      lex_auxiliary parse_auxiliary bibtex_ast sym
@@ -346,15 +351,15 @@ sub ACTION_create_library {
     my @objects = map { "btparse/src/$_.o" } @modules;
 
     my $libpath = $self->notes('lib_path');
-    $libpath = catfile($libpath, "libbtparse$LIBEXT");
-    my $libfile = "btparse/src/libbtparse$LIBEXT";
+    $libpath = catfile($libpath, $SONAME);
+    my $libfile = "btparse/src/$SONAME";
 
     my $extra_linker_flags = "";
     if ($^O =~ /darwin/) {
        my $abs_path = abs_path($libfile);
        $extra_linker_flags = "-install_name $abs_path";
     } elsif ($LIBEXT eq ".so") {
-        $extra_linker_flags = "-Wl,-soname,libbtparse$LIBEXT";
+        $extra_linker_flags = "-Wl,-soname,$SONAME";
     }
 
     if (!$self->up_to_date(\@objects, $libfile)) {
@@ -364,6 +369,14 @@ sub ACTION_create_library {
                           extra_linker_flags => $extra_linker_flags);
     }
 
+    if ($symlink_exists) {
+      my $olddir = getcwd;
+      chdir ("btparse/src");
+      unlink("libbtparse$LIBEXT");
+      symlink ($SONAME, "libbtparse$LIBEXT") or die("$!");
+      chdir ($olddir);
+    }
+
     my $libdir = catdir($self->blib, 'usrlib');
     mkpath( $libdir, 0, 0777 ) unless -d $libdir;