From 602519db1272bc3eee8b71f05f97fe3c9c8bc2d9 Mon Sep 17 00:00:00 2001
From: CismonX <admin@cismon.net>
Date: Sat, 12 Jul 2025 12:53:16 +0800
Subject: [PATCH] build: misc refactor

EX_DEP():
- Do not generate feature check code if `feat-names` is empty.
- Improve docs.

others:
- Reuse `$host_os` for system type check result.
---
 configure.ac        | 10 +++++-----
 m4/configure_ext.m4 | 14 ++++++++------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/configure.ac b/configure.ac
index 0cf4d05..6bbed6c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,11 +23,11 @@ LT_INIT([disable-static dlopen])
 
 AC_CANONICAL_HOST
 AS_CASE(["${host_os}"], [linux*], [
-    AS_VAR_SET([host_os_is_linux], [yes])
+    AS_VAR_SET([host_os], [linux])
 ], [freebsd*], [
-    AS_VAR_SET([host_os_is_freebsd], [yes])
+    AS_VAR_SET([host_os], [freebsd])
 ], [
-    AC_MSG_ERROR(m4_normalize([Unsupported platform "${host_os}".]))
+    AC_MSG_ERROR([Unsupported platform "${host_os}".])
 ])
 
 # -- Checks for programs --
@@ -54,7 +54,7 @@ EX_FEAT([bookmarkfs-mount], [NE], [the mount.bookmarkfs program], [
 
 EX_FEAT([sandbox], [YDE], [sandboxing])
 
-AS_VAR_IF([host_os_is_linux], [yes], [
+AS_VAR_IF([host_os], [linux], [
     EX_FEAT([sandbox-landlock], [YD], [using Landlock for sandboxing])
 ])
 
@@ -95,7 +95,7 @@ AX_PTHREAD
 
 EX_DEP([fuse3], [>= 3.5], [fuse3 library], , [bookmarkfs-mount])
 
-AS_VAR_IF([host_os_is_linux], [yes], [
+AS_VAR_IF([host_os], [linux], [
     EX_DEP([libseccomp], [>= 2.5], [libseccomp library], , [sandbox])
 ])
 
diff --git a/m4/configure_ext.m4 b/m4/configure_ext.m4
index a6c07ad..e153dd4 100644
--- a/m4/configure_ext.m4
+++ b/m4/configure_ext.m4
@@ -48,33 +48,35 @@ AC_DEFUN([EX_FEAT], [
 ])
 
 dnl
-dnl  EX_DEP(pkg-name, version, pkg-desc, [action-if-found],
-dnl         [required-by-features]...)
+dnl  EX_DEP(pkg-name, version, pkg-desc, [action-if-found], [feat-names]...)
 dnl
 dnl  Check whether a package exists with `pkg-config`,
 dnl  and provide an option to specify the package's custom install location.
 dnl
+dnl  If at least one feature specified in `feat-names` is enabled,
+dnl  automatically enable checking the package, and fail if not found.
+dnl
 AC_DEFUN([EX_DEP], [
     AC_ARG_WITH([$1], m4_normalize([
         AS_HELP_STRING([--with-m4_translit([$1], [_], [-])[[=PKGCONFIGDIR]]],
                 [pkg-config search path for $3])
     ]), , [
         AS_VAR_SET([with_$1], [no])
-        m4_foreach([feat_name_], [m4_shiftn(4, $@)], [
+        m4_ifnblank([$5], m4_foreach([feat_name_], [m4_shiftn(4, $@)], [
             AS_VAR_IF([enable_]m4_translit(feat_name_, [-], [_]), [yes], [
                 AS_VAR_SET([with_$1], [yes])
             ])
-        ])
+        ]))
     ])
     AS_VAR_IF([with_$1], [no], [
-        m4_foreach([feat_name_], [m4_shiftn(4, $@)], [
+        m4_ifnblank([$5], m4_foreach([feat_name_], [m4_shiftn(4, $@)], [
             AS_VAR_IF([enable_]m4_translit(feat_name_, [-], [_]), [yes], [
                 AC_MSG_ERROR(m4_normalize([
                     Bad option '[--without-]feat_name_'. The $3 is mandatory
                     for AS_VAR_GET([desc_]m4_translit(feat_name_, [-], [_])).
                 ]))
             ])
-        ])
+        ]))
     ], [
         AS_VAR_SET([old_pkg_config_path_], ["${PKG_CONFIG_PATH}"])
         AS_VAR_IF([with_$1], [yes], , [