From 4cbbb64e21c4bc1e9f7c07a13f7a71db775c0e18 Mon Sep 17 00:00:00 2001
From: Leo Yuriev <leo@yuriev.ru>
Date: Mon, 6 Jun 2016 01:40:41 +0300
Subject: [PATCH] mdbx: ban the compilers older than GCC 4.2 or incompatible
 with it.

Change-Id: I30cfc04b086116652b3c40d76e1def8428b0dcd7
---
 Makefile |  1 +
 reopen.h | 19 ++++++++++++++-----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 0235df50..90adc7b7 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,5 @@
 # GNU Makefile for libmdbx (reliable lightning memory-mapped DB library for Linux).
+# https://github.com/ReOpen/libmdbx
 
 ########################################################################
 # Configuration. The compiler options must enable threaded compilation.
diff --git a/reopen.h b/reopen.h
index 733886f9..313eb0a5 100644
--- a/reopen.h
+++ b/reopen.h
@@ -21,7 +21,16 @@
 /* LY: Please do not ask us for Windows support, just never!
  * But you can make a fork for Windows, or become maintainer for FreeBSD... */
 #ifndef __gnu_linux__
-#	error "ReOpenLDAP branch supports only GNU Linux"
+#	error "MDBX supports only GNU Linux"
+#endif
+
+#if !defined(__GNUC__) || __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 2)
+	/* LY: Actualy MDBX was not tested with compilers
+	 *     older than GCC 4.4 from RHEL6, and clang 3.6 from Ubuntu.
+	 * But you could remove this #error and try to continue at your own risk.
+	 * In such case please don't rise up an issues related ONLY to old compilers.
+	 */
+#	error "MDBX required at least GCC 4.2 compatible C/C++ compiler."
 #endif
 
 #ifndef _REOPEN_H
@@ -31,14 +40,14 @@
 #	define _GNU_SOURCE
 #endif
 
+#if !defined(GCC_VERSION) && defined(__GNUC__)
+#	define GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
+#endif /* GCC_VERSION */
+
 #ifndef __has_attribute
 #	define __has_attribute(x) (0)
 #endif
 
-#if !defined(GCC_VERSION) && defined(__GNUC__)
-#	define GCC_VERSION (__GNUC__ * 1000 + __GNUC_MINOR__)
-#endif /* GCC_VERSION */
-
 #if !defined(__thread) && (defined(_MSC_VER) || defined(__DMC__))
 #	define __thread __declspec(thread)
 #endif