From 9a4b4a3d3b27fe4a7ff6d0b8724ce1c06b5917eb Mon Sep 17 00:00:00 2001
From: David Levine <levinedl@acm.org>
Date: Sun, 4 Dec 2016 17:02:13 -0500
Subject: [PATCH] Enabled detection of tm_gmtoff on _GNU_SOURCE platforms,
 e.g., Linux.

By temporarily adding $AM_CPPFLAGS to CPPFLAGS.
---
 configure.ac | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index 234ff3c4..7778d2f3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -587,13 +587,15 @@ dnl ----------------
 dnl CHECK STRUCTURES
 dnl ----------------
 
-dnl FIXME: This test could work on Linux if _BSD_SOURCE was #define'd
-dnl according to localtime(3).
-dnl
 dnl For platforms such as FreeBSD that have tm_gmtoff in struct tm.
 dnl (FreeBSD has a timezone() function but not a timezone global
 dnl variable that is visible).
-AC_CHECK_MEMBERS([struct tm.tm_gmtoff],,,[#include <time.h>])
+dnl On Linux, $AM_CPPFLAGS contains -D_GNU_SOURCE, which makes
+dnl tm_gmtoff visible.
+nmh_saved_CPPFLAGS="$CPPFLAGS"
+CPPFLAGS="$AM_CPPFLAGS $CPPFLAGS"
+AC_CHECK_MEMBER([struct tm.tm_gmtoff],,,[[#include <time.h>]])
+CPPFLAGS="$nmh_saved_CPPFLAGS"
 
 AC_STRUCT_DIRENT_D_TYPE
 
-- 
2.56.0