build: refactor configuration scripts

- Move common `AC_DEFINE()` usage to `EX_FEAT()`.
- Remove unused argument `action-if-disabled` for `EX_FEAT()`.
- Conditionally enable features by default.

configure.ac

@@ -40,81 +40,50 @@ AC_PROG_MAKE_SET
 
 # -- Checks for features --
 
-EX_FEAT([bookmarkfs-util], [no], [the BookmarkFS utility library])
+EX_FEAT([bookmarkfs-util], [no], [the BookmarkFS utility library], , [1])
 
-EX_FEAT([bookmarkctl], [no], [the bookmarkctl program])
+EX_FEAT([bookmarkctl], [no], [the bookmarkctl program], , [1])
 
 EX_FEAT([bookmarkfs-fsck], [no], [the fsck.bookmarkfs program], [
     AS_VAR_SET([enable_bookmarkfs_util],  [yes])
-])
+    AS_VAR_SET([enable_interactive_fsck], [yes])
+], [1])
 
-EX_FEAT([bookmarkfs-mkfs], [no], [the mkfs.bookmarkfs program])
+EX_FEAT([bookmarkfs-mkfs], [no], [the mkfs.bookmarkfs program], , [1])
 
 EX_FEAT([bookmarkfs-mount], [no], [the mount.bookmarkfs program], [
     AS_VAR_SET([enable_bookmarkfs_util], [yes])
-])
+], [1])
 
-EX_FEAT([sandbox], [yes], [sandboxing], [
-    AC_DEFINE([BOOKMARKFS_SANDBOX], [1],
-            [Define to 1 if sandboxing is enabled.])
-])
+EX_FEAT([sandbox], [yes], [sandboxing])
 
 AS_VAR_IF([host_os_is_linux], [yes], [
-    EX_FEAT([sandbox-landlock], [yes], [Landlock features for sandboxing], [
-        AC_DEFINE([BOOKMARKFS_SANDBOX_LANDLOCK], [1],
-                [Define to 1 if Landlock is enabled for sandboxing.])
-    ])
+    EX_FEAT([sandbox-landlock], [yes], [Landlock features for sandboxing])
 ])
 
-EX_FEAT([xxhash-inline], [no], [using xxhash as a header-only library], [
-    AC_DEFINE([BOOKMARKFS_XXHASH_INLINE], [1],
-            [Define to 1 if using xxhash as a header-only library.])
-])
+EX_FEAT([xxhash-inline], [no], [using xxhash as a header-only library])
 
-EX_FEAT([bookmarkfs-debug], [no], [debugging features for BookmarkFS], [
-    AC_DEFINE([BOOKMARKFS_DEBUG], [1],
-            [Define to 1 if BookmarkFS debugging is enabled.])
-])
+EX_FEAT([bookmarkfs-debug], [no], [debugging features for BookmarkFS])
 
 EX_FEAT([backend-firefox], [no], [Firefox backend], [
     AS_VAR_SET([enable_bookmarkfs_util],       [yes])
-])
+    AS_VAR_SET([enable_backend_firefox_write], [yes])
+], [1])
 
-EX_FEAT([backend-firefox-write], [yes],
-        [write support for the Firefox backend],
-[
-    AC_DEFINE([BOOKMARKFS_BACKEND_FIREFOX_WRITE], [1],
-            [Define to 1 if the Firefox backend supports writing.])
-])
+EX_FEAT([backend-firefox-write], , [write support for the Firefox backend])
 
 EX_FEAT([backend-chromium], [no], [Chromium backend], [
     AS_VAR_SET([enable_bookmarkfs_util],        [yes])
-])
+    AS_VAR_SET([enable_backend_chromium_write], [yes])
+], [1])
 
-EX_FEAT([backend-chromium-write], [yes],
-        [write support for the Chromium backend],
-[
-    AC_DEFINE([BOOKMARKFS_BACKEND_CHROMIUM_WRITE], [1],
-            [Define to 1 if the Chromium backend supports writing.])
-])
+EX_FEAT([backend-chromium-write], , [write support for the Chromium backend])
 
-EX_FEAT([native-watcher], [yes], [platform-specific file watcher], [
-    AC_DEFINE([BOOKMARKFS_NATIVE_WATCHER], [1],
-            [Define to 1 if platform-specific file watcher is enabled.])
-])
+EX_FEAT([native-watcher], [yes], [platform-specific file watcher])
 
-EX_FEAT([interactive-fsck], [yes],
-        [interactive features for fsck.bookmarkfs],
-[
-    AS_VAR_IF([enable_bookmarkfs_fsck], [no], [
-        AS_VAR_SET([enable_interactive_fsck], [no])
-    ], [
-        AC_DEFINE([BOOKMARKFS_INTERACTIVE_FSCK], [1],
-                [Define to 1 if interactive fsck features are enabled.])
-    ])
-])
+EX_FEAT([interactive-fsck], , [interactive features for fsck.bookmarkfs])
 
-EX_FEAT([fsck-handler-tcl], [no], [Tcl-based fsck handler])
+EX_FEAT([fsck-handler-tcl], [no], [Tcl-based fsck handler], , [1])
 
 # -- Checks for libraries --
 

m4/configure_ext.m4

@@ -8,8 +8,8 @@ dnl  This file is offered as-is, without any warranty.
 dnl
 
 dnl
-dnl  EX_FEAT(feature, default-value, description, [action-if-enabled],
-dnl          [action-if-disabled])
+dnl  EX_FEAT(feature, [default-value], description, [action-if-enabled],
+dnl          [no-ac-define])
 dnl
 dnl  Provide an option to enable or disable a feature.
 dnl
@@ -19,15 +19,19 @@ AC_DEFUN([EX_FEAT], [
     AC_MSG_CHECKING(m4_normalize([if $3 is enabled]))
     AC_ARG_ENABLE([$1], m4_normalize([
         AS_HELP_STRING([--]arg_action_[-$1], arg_action_ [$3])
-    ]), , [
+    ]), , m4_ifnblank([$2], [
         AS_VAR_SET([enable_]feat_name_, [$2])
-    ])
-    AS_VAR_IF([enable_]feat_name_, [no], [
-        AC_MSG_RESULT([no])
-        $5
-    ], [
+    ]))
+    AS_VAR_IF([enable_]feat_name_, [yes], [
         AC_MSG_RESULT([yes])
         $4
+        m4_ifblank([$5], [
+            AC_DEFINE(m4_if(m4_substr(feat_name_, 0, 10), [bookmarkfs], ,
+                            [BOOKMARKFS_])[]m4_toupper(feat_name_),
+                    [1], [Define to 1 if $3 is enabled.])
+        ])
+    ], [
+        AC_MSG_RESULT([no])
     ])
     AS_VAR_SET([desc_]feat_name_, ["$3"])
     m4_popdef([arg_action_])