Assume that callbacks are not broken in OpenLDAP when cross-compiling

[krnowak]

This adds a LDAP_HAVE_CONNCB_CROSS variable that will be used instead of the runtime check for a broken connection callbacks in ldap library. Set it to yes to assume that connection callbacks are working.

This allows the project to be configured successfully when cross-compiling.

If we do cross-compiling against a known broken version of OpenLDAP, we can do export ac_cv_member_struct_ldap_conncb_lc_arg=no before running configure. This is rather unlikely now, as the test was done to detect a bug that was fixed 16 years ago.

This allows the project to be configured successfully when cross-compiling, without disabling connection callbacks.

Tested locally in Flatcar (flatcar/scripts#2501)

[chewi]

Given that you can already override the result with ac_cv_member_struct_ldap_conncb_lc_arg, I don't think an additional variable is really needed, but let's see what the maintainers think.

[krnowak]

Given that you can already override the result with ac_cv_member_struct_ldap_conncb_lc_arg, I don't think an additional variable is really needed, but let's see what the maintainers think.

This can override a result of AC_CHECK_MEMBERS([struct ldap_conncb.lc_arg], ...), but there is nothing to override a result of AC_RUN_IFELSE that is being run when ac_cv_member_struct_ldap_conncb_lc_arg is "yes".

[chewi]

Okay, but setting it to no is what would help here. When cross-compiling, you can either:

• Let it do the AC_CHECK_MEMBERS check, and if yes, call the cross action, which assumes your OpenLDAP is not broken.
• Manually set ac_cv_member_struct_ldap_conncb_lc_arg=no, bypassing the whole thing, because you know your OpenLDAP is broken.

[krnowak]

Okay, but setting it to no is what would help here. When cross-compiling, you can either:

• Let it do the AC_CHECK_MEMBERS check, and if yes, call the cross action, which assumes your OpenLDAP is not broken.
• Manually set ac_cv_member_struct_ldap_conncb_lc_arg=no, bypassing the whole thing, because you know your OpenLDAP is broken.

Setting it to no means that we do not use LDAP connection callbacks. It indeed means that runtime check for broken OpenLDAP does not happen, but it is a lazy solution for making cross-compilation to work, because it results in using a sub-par solution instead of connection callbacks (as far as I understand it, of course). But if I know that our OpenLDAP is not broken and I want to cross-compile the project, then without this PR this is not possible to have - AC_CHECK_MEMBERS will set the ac_cv_member_struct_ldap_conncb_lc_arg=yes, but AC_RUN_IFELSE will bail out, because of empty "action-if-cross-compiling".

Honestly, I'd prefer to drop the AC_RUN_IFELSE - it is a check for an OpenLDAP bug that was fixed 16 years ago, I think.

[chewi]

Our wires are crossed. 😅

If you want the callbacks, then you wouldn't set it at all. I still think a change is needed, I just think it should be:

@@ -80,7 +81,8 @@ AC_CHECK_MEMBERS([struct ldap_conncb.lc_arg],
                    [AC_DEFINE([HAVE_LDAP_CONNCB], [1],
                      [Define if LDAP connection callbacks are available])],
                    [AC_MSG_WARN([Found broken callback implementation])],
-                   [])],
+                   [AC_DEFINE([HAVE_LDAP_CONNCB], [1],
+                     [Define if LDAP connection callbacks are available])])],
                  [], [[#include <ldap.h>]])
 
 AC_CHECK_TYPE([LDAPDerefRes],

[krnowak]

Oh, I finally got what you meant. :)

Yeah, true, that'd be simpler. I'll make the change.

[krnowak]

PR updated. I'm wondering if it could be also backported to 2.9 and 2.10 branches.

[krnowak]

@sumit-bose: Thanks for the review. PR updated.

[sumit-bose]

Hi,

thank you for the update, ACK.

bye,
Sumit

[alexey-tikhonov]

Pushed PR: #7743

• master
  • 39f9ff8 - Assume that callbacks are not broken in OpenLDAP when cross-compiling
• sssd-2-10
  • 8bac60a - Assume that callbacks are not broken in OpenLDAP when cross-compiling
• sssd-2-9
  • ee195e7 - Assume that callbacks are not broken in OpenLDAP when cross-compiling