configure: don't probe for libldap_r if libldap is 2.5 or newer.

In OpenLDAP 2.5 and later, libldap itself is always thread-safe and
there's never a libldap_r.  Our existing coding dealt with that
by assuming it wouldn't find libldap_r if libldap is thread-safe.
But that rule fails to cope if there are multiple OpenLDAP versions
visible, as is likely to be the case on macOS in particular.  We'd
end up using shiny new libldap in the backend and a hoary libldap_r
in libpq.

Instead, once we've found libldap, check if it's >= 2.5 (by
probing for a function introduced then) and don't bother looking
for libldap_r if so.  While one can imagine library setups that
this'd still give the wrong answer for, they seem unlikely to
occur in practice.

Per report from Peter Eisentraut.  Back-patch to all supported branches.

Discussion: https://postgr.es/m/fedacd7c-2a38-25c9-e7ff-dea549d0e979@enterprisedb.com

diff --git a/configure b/configure
index 547d05c4c4e89fda387e6d42bc7f6711135379a3..2420030cfba69427419deafb72c326c7a6b49cb4 100755 (executable)
--- a/configure
+++ b/configure
@@ -10696,7 +10696,18 @@ else
 fi
 
     LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
-    if test "$enable_thread_safety" = yes; then
+    # The separate ldap_r library only exists in OpenLDAP < 2.5, and if we
+    # have 2.5 or later, we shouldn't even probe for ldap_r (we might find a
+    # library from a separate OpenLDAP installation).  The most reliable
+    # way to check that is to check for a function introduced in 2.5.
+    ac_fn_c_check_func "$LINENO" "ldap_verify_credentials" "ac_cv_func_ldap_verify_credentials"
+if test "x$ac_cv_func_ldap_verify_credentials" = xyes; then :
+  thread_safe_libldap=yes
+else
+  thread_safe_libldap=no
+fi
+
+    if test "$enable_thread_safety" = yes -a "$thread_safe_libldap" = no; then
       # Use ldap_r for FE if available, else assume ldap is thread-safe.
       # On some platforms ldap_r fails to link without PTHREAD_LIBS.
       LIBS="$_LIBS"

diff --git a/configure.in b/configure.in
index 086669126fda42544e297567ebcec89def3ce1c7..112611d8a6ca791ff230754a48a2c6004d34fa0c 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -1202,7 +1202,14 @@ if test "$with_ldap" = yes ; then
         [AC_MSG_ERROR([library 'ldap' is required for LDAP])],
         [$EXTRA_LDAP_LIBS])
     LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
-    if test "$enable_thread_safety" = yes; then
+    # The separate ldap_r library only exists in OpenLDAP < 2.5, and if we
+    # have 2.5 or later, we shouldn't even probe for ldap_r (we might find a
+    # library from a separate OpenLDAP installation).  The most reliable
+    # way to check that is to check for a function introduced in 2.5.
+    AC_CHECK_FUNC([ldap_verify_credentials],
+         [thread_safe_libldap=yes],
+         [thread_safe_libldap=no])
+    if test "$enable_thread_safety" = yes -a "$thread_safe_libldap" = no; then
       # Use ldap_r for FE if available, else assume ldap is thread-safe.
       # On some platforms ldap_r fails to link without PTHREAD_LIBS.
       LIBS="$_LIBS"