Enable --version-sort on systems without strverscmp()

The --version-sort option requires strverscmp(), but this is a glibc
extension that does not exist on OpenBSD and other systems. To enable
--version-sort on those systems, provide an internal implementation of
strverscmp(). The implementation is from the musl C library and is
MIT-licensed.

The build process remains the same: the verscmp flag should be set to 1
only if strverscmp() is available in libc. If verscmp is 0, then the
internal implementation is used.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/feh.h b/src/feh.h
index a76d66f..e735871 100644
--- a/src/feh.h
+++ b/src/feh.h
@@ -31,7 +31,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  * strverscmp(3) is a GNU extension. In most supporting C libraries it
  * requires _GNU_SOURCE to be defined.
  */
-#ifdef HAVE_VERSCMP
+#ifdef HAVE_STRVERSCMP
 #define _GNU_SOURCE
 #endif
 
@@ -182,6 +182,9 @@ gib_list *feh_list_jump(gib_list * root, gib_list * l, int direction, int num);
 #ifdef HAVE_INOTIFY
 void feh_event_handle_inotify(void);
 #endif
+#ifndef HAVE_STRVERSCMP
+int strverscmp(const char *l0, const char *r0);
+#endif
 
 /* Imlib stuff */
 extern Display *disp;