autotools: attempt to find OpenSSL via homebrew on macOS

When compiling for macOS, where users will likely have OpenSSL installed
via brew, rather than available on the system, use brew  --prefix to
figure out where OpenSSL is, and then augment the pkg-config path so
that libs are found.

diff --git a/m4/libevent_openssl.m4 b/m4/libevent_openssl.m4
index a5ea67620067fb7301b0f420152300e95ef8a2b4..b95d24496222b562081138d1d96bf72b845865e7 100644 (file)
--- a/m4/libevent_openssl.m4
+++ b/m4/libevent_openssl.m4
@@ -3,6 +3,33 @@ dnl OpenSSL support
 AC_DEFUN([LIBEVENT_OPENSSL], [
 AC_REQUIRE([NTP_PKG_CONFIG])dnl
 
+case "$host_os" in
+    darwin*)
+    dnl when compiling for Darwin, attempt to find OpenSSL using brew.
+    dnl We append the location given by brew to PKG_CONFIG_PATH path
+    dnl and then export it, so that it can be used in detection below.
+    AC_CHECK_PROG([BREW],brew, brew)
+    if test x$BREW = xbrew; then
+        openssl_prefix=$($BREW --prefix openssl 2>/dev/null)
+        if test x$openssl_prefix != x; then
+            OPENSSL_LIBS=`$PKG_CONFIG --libs openssl 2>/dev/null`
+            case "$OPENSSL_LIBS" in
+             dnl only if openssl is not in PKG_CONFIG_PATH already
+             '')
+                if test x$PKG_CONFIG_PATH != x; then
+                    PKG_CONFIG_PATH="$PKG_CONFIG_PATH:"
+                fi
+                OPENSSL_PKG_CONFIG="$openssl_prefix/lib/pkgconfig"
+                PKG_CONFIG_PATH="$PKG_CONFIG_PATH$OPENSSL_PKG_CONFIG"
+                export PKG_CONFIG_PATH
+                AC_MSG_NOTICE([PKG_CONFIG_PATH has been set to $PKG_CONFIG_PATH (added openssl from brew)])
+                ;;
+            esac
+        fi
+    fi
+    ;;
+esac
+
 case "$enable_openssl" in
  yes)
     have_openssl=no
@@ -27,7 +54,7 @@ case "$enable_openssl" in
        LIBS=""
        OPENSSL_LIBS=""
        for lib in crypto eay32; do
-               # clear cache
+               dnl clear cache
                unset ac_cv_search_SSL_new
                AC_SEARCH_LIBS([SSL_new], [ssl ssl32],
                    [have_openssl=yes
@@ -47,15 +74,15 @@ case "$enable_openssl" in
     AC_SUBST(OPENSSL_LIBS)
     case "$have_openssl" in
      yes)  AC_DEFINE(HAVE_OPENSSL, 1, [Define if the system has openssl]) ;;
-     *) AC_MSG_ERROR([openssl is a must but can not be found. You should add the \
-directory containing `openssl.pc' to the `PKG_CONFIG_PATH' environment variable, \
-or set `CFLAGS' and `LDFLAGS' directly for openssl, or use `--disable-openssl' \
-to disable support for openssl encryption])
+     *) AC_MSG_ERROR([OpenSSL could not be found. You should add the directory \
+     containing 'openssl.pc' to the 'PKG_CONFIG_PATH' environment variable, set \
+     'CFLAGS' and 'LDFLAGS' directly, or use '--disable-openssl' to disable \
+     support for OpenSSL encryption])
        ;;
     esac
     ;;
 esac
 
-# check if we have and should use openssl
+dnl check if we have and should use OpenSSL
 AM_CONDITIONAL(OPENSSL, [test "$enable_openssl" != "no" && test "$have_openssl" = "yes"])
 ])