From 3c43b016e9767df74909ea5644399e8872e38c97 Mon Sep 17 00:00:00 2001
From: Frank Lichtenheld <frank@lichtenheld.com>
Date: Wed, 26 Jun 2024 18:19:21 +0200
Subject: [PATCH] configure: Try to detect LZO with pkg-config

On most systems this should work just fine.

v2:
 - simplify code by removing -llzo special handling
v3:
 - reintroduce support for autodetection without pkg-config,
   no need to break backwards compatibility right now
v7:
 - Handle case correctly where lzo/lzo1x.h can not be included
   at all. On most distros this works even though the .pc
   file suggests to use it without. We had some partly
   solution for that but it wasn't really working.
v8:
 - Handle systems that do not implicitly include limits.h
   in configure test builds.
   lzodefs.h usually relies on lzoconf.h to include it.

Change-Id: I1c038dc4ec80d3499582d81eee61fee74f26e693
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20240626161921.179301-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg28848.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 0ea51261d096b54281287bbd2a6899041c4dbd43)
---
 config.h.cmake.in |  3 ---
 configure.ac      | 24 ++++++++++++++++++++----
 src/openvpn/lzo.h |  8 +++-----
 3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/config.h.cmake.in b/config.h.cmake.in
index e0abdb0a..cedc5bee 100644
--- a/config.h.cmake.in
+++ b/config.h.cmake.in
@@ -175,9 +175,6 @@ don't. */
 /* Define to 1 if you have the <linux/types.h> header file. */
 #cmakedefine HAVE_LINUX_TYPES_H
 
-/* Define to 1 if you have the <lzoconf.h> header file. */
-#define HAVE_LZO_CONF_H
-
 /* Define to 1 if you have the <lzo1x.h> header file. */
 #define HAVE_LZO1X_H 1
 
diff --git a/configure.ac b/configure.ac
index f56d0ccf..df16c439 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1152,8 +1152,17 @@ fi
 
 AC_ARG_VAR([LZO_CFLAGS], [C compiler flags for lzo])
 AC_ARG_VAR([LZO_LIBS], [linker flags for lzo])
-have_lzo="yes"
-if test -z "${LZO_LIBS}"; then
+if test -z "${LZO_CFLAGS}" -a -z "${LZO_LIBS}"; then
+    # if the user did not explicitly specify flags, try to autodetect
+    PKG_CHECK_MODULES([LZO],
+		[lzo2],
+		[have_lzo="yes"],
+		[]
+    )
+
+    if test "${have_lzo}" != "yes"; then
+	# try to detect without pkg-config
+	have_lzo="yes"
 	AC_CHECK_LIB(
 		[lzo2],
 		[lzo1x_1_15_compress],
@@ -1165,6 +1174,10 @@ if test -z "${LZO_LIBS}"; then
 			[have_lzo="no"]
 		)]
 	)
+    fi
+else
+    # assume the user configured it correctly
+    have_lzo="yes"
 fi
 if test "${have_lzo}" = "yes"; then
 	saved_CFLAGS="${CFLAGS}"
@@ -1175,8 +1188,11 @@ if test "${have_lzo}" = "yes"; then
 		[AC_CHECK_HEADERS(
 			[lzo1x.h],
 			,
-			[AC_MSG_ERROR([lzo1x.h is missing])]
-		)]
+			[AC_MSG_ERROR([lzo1x.h is missing])],
+                        [#include <limits.h>
+                         #include <lzodefs.h>
+                         #include <lzoconf.h>]
+		)],
 	)
 	CFLAGS="${saved_CFLAGS}"
 fi
diff --git a/src/openvpn/lzo.h b/src/openvpn/lzo.h
index 62d73a1b..c2715276 100644
--- a/src/openvpn/lzo.h
+++ b/src/openvpn/lzo.h
@@ -37,17 +37,15 @@
  * @addtogroup compression
  * @{
  */
-#if defined(HAVE_LZO_CONF_H)
+#if defined(HAVE_LZO_LZO1X_H)
+#include <lzo/lzo1x.h>
+#elif defined(HAVE_LZO1X_H)
 /* The lzo.h magic gets confused and still wants
  * to include lzo/lzoconf.h even if our include paths
  * are setup to include the paths without lzo/
  */
 #include <lzodefs.h>
 #include <lzoconf.h>
-#endif
-#if defined(HAVE_LZO_LZO1X_H)
-#include <lzo/lzo1x.h>
-#elif defined(HAVE_LZO1X_H)
 #include <lzo1x.h>
 #endif