Compile IPA modules with C11 extensions

- define __STDC_WANT_LIB_EXT1__ to get C11 extensions like memset_s() for
  Samba's ZERO_STRUCT() macro, see
  https://en.cppreference.com/w/c/string/byte/memset
- _DEFAULT_SOURCE enables features like htole16() from endian.h, see
  http://man7.org/linux/man-pages/man3/endian.3.html
- _POSIX_C_SOURCE >= 200809 enables features like strndup() from string.h,
  see http://man7.org/linux/man-pages/man3/strndup.3.html
- time_t is no longer implicitly defined, include time.h
- typeof() is only available as GNU extension. Use explicit types
  instead of generic __typeof__().

Fixes: https://pagure.io/freeipa/issue/7858
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

configure.ac

@@ -18,15 +18,21 @@ AC_CONFIG_HEADERS([config.h])
 AM_INIT_AUTOMAKE([foreign 1.9 tar-pax])
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES])
 
+dnl enable C11 extensions for features like memset_s()
+CFLAGS+=" -D__STDC_WANT_LIB_EXT1__=1"
+dnl enable features like htole16()
+CFLAGS+=" -D_DEFAULT_SOURCE=1"
+dnl Enable features like strndup()
+CFLAGS+=" -D_POSIX_C_SOURCE=200809L"
+dnl fail hard when includes statements are missing
+CFLAGS+=" -Werror=implicit-function-declaration"
+
 AC_PROG_CC_C99
 AC_DISABLE_STATIC
 LT_INIT
 
 AC_HEADER_STDC
 
-dnl fail hard when includes statements are missing
-CFLAGS+=" -Werror=implicit-function-declaration"
-
 PKG_PROG_PKG_CONFIG
 
 AC_ARG_ENABLE([server],

daemons/ipa-slapi-plugins/libotp/otp_config.c

@@ -217,7 +217,7 @@ struct otp_config *otp_config_init(Slapi_ComponentId *plugin_id)
     void *node = NULL;
     int search_result = 0;
 
-    cfg = (typeof(cfg)) slapi_ch_calloc(1, sizeof(*cfg));
+    cfg = (struct otp_config *) slapi_ch_calloc(1, sizeof(*cfg));
     cfg->plugin_id = plugin_id;
 
     /* Build the config table. */
@@ -229,7 +229,7 @@ struct otp_config *otp_config_init(Slapi_ComponentId *plugin_id)
             struct record *rec;
 
             /* Create the config entry. */
-            rec = (typeof(rec)) slapi_ch_calloc(1, sizeof(*rec));
+            rec = (struct record *) slapi_ch_calloc(1, sizeof(*rec));
             rec->spec = specs[i];
             rec->sdn = make_sdn(rec->spec->prefix, sfx);
 

util/ipa_krb5.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <time.h>
 #include <lber.h>
 #include <krb5/krb5.h>
 #include <kdb.h>