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 8a9d7b4149c072bde500f5eb680a7c9eec4da4de..b405f4acf3050dbb77bbe27907c83b6cdae1ad23 100755 (executable)
--- a/configure
+++ b/configure
@@ -12397,7 +12397,18 @@ _ACEOF
 fi
 done
 
-    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 bb7c4c77f0aca35b28e02524e00711c49d5f04c9..c2e725223afdae194b0c9eadebbfa6c2990d895a 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -1311,7 +1311,14 @@ if test "$with_ldap" = yes ; then
     LDAP_LIBS_BE="-lldap $EXTRA_LDAP_LIBS"
     # This test is carried out against libldap.
     AC_CHECK_FUNCS([ldap_initialize])
-    if test "$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"