From 3a7923cb2aff29ef4d83f7c8590c76fc4ff12c58 Mon Sep 17 00:00:00 2001
From: Vincent Bernat <vincent@bernat.im>
Date: Wed, 13 Jun 2018 08:06:45 +0200
Subject: [PATCH] build: also test directly for -lcap when no pkg-config

---
 configure.ac |  4 +---
 m4/libcap.m4 | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)
 create mode 100644 m4/libcap.m4

diff --git a/configure.ac b/configure.ac
index 1af248b5..9b40473e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -226,9 +226,7 @@ PKG_CHECK_MODULES([check], [check >= 0.9.4], [have_check=yes], [have_check=no])
 
 # Third-party libraries
 lldp_CHECK_LIBEVENT
-PKG_CHECK_MODULES([libcap], [libcap >= 2], [
-  AC_DEFINE([HAVE_LINUX_CAPABILITIES], 1, [Define to indicate support of linux capabilities])
-], [:])
+lldp_CHECK_LIBCAP
 
 # Compatibility with pkg.m4 < 0.27
 m4_ifdef([PKG_INSTALLDIR], [PKG_INSTALLDIR],
diff --git a/m4/libcap.m4 b/m4/libcap.m4
new file mode 100644
index 00000000..78003364
--- /dev/null
+++ b/m4/libcap.m4
@@ -0,0 +1,25 @@
+#
+# lldp_CHECK_LIBCAP
+#
+
+AC_DEFUN([lldp_CHECK_LIBCAP], [
+    PKG_CHECK_MODULES([libcap], [libcap >= 2], [
+       AC_DEFINE([HAVE_LINUX_CAPABILITIES], 1, [Define to indicate support of linux capabilities])
+    ], [
+      libcap_LIBS=-lcap
+      libcap_CFLAGS=
+      _save_libs="$LIBS"
+      LIBS="$LIBS ${libcap_LIBS}"
+      AC_MSG_CHECKING([libcap (without pkg-config)])
+      AC_TRY_LINK_FUNC([cap_set_proc], [
+         AC_DEFINE([HAVE_LINUX_CAPABILITIES], 1, [Define to indicate support of linux capabilities])
+         AC_MSG_RESULT(yes)
+      ], [
+         libcap_LIBS=
+         AC_MSG_RESULT(no)
+      ])
+      LIBS="$_save_libs"
+    ])
+    AC_SUBST([libcap_LIBS])
+    AC_SUBST([libcap_CFLAGS])
+])
-- 
2.39.5