diff --git a/configure b/configure
index 551a963ae06a3624..06ba2c4ebde3e9ab 100755
--- a/configure
+++ b/configure
@@ -16341,8 +16341,9 @@ else
 /* end confdefs.h.  */
 #include <stdio.h>
                                     #include <signal.h>
-                                    segv() { exit(1); }
-                                    main() { char b[10]; signal(SIGSEGV,segv); snprintf(b,10,"%s",NULL); exit(0); }
+                                    #include <stdlib.h>
+                                    void segv() { exit(1); }
+                                    int main() { char b[10]; signal(SIGSEGV,segv); snprintf(b,10,"%s",NULL); exit(0); }
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
@@ -16373,9 +16374,10 @@ else
 #include <stdio.h>
                                     #include <signal.h>
                                     #include <stdarg.h>
-                                    segv() { exit(1); }
-                                    expand(char *f,...) { va_list ap; char b[10]; va_start(ap,f); vsnprintf(b,10,f,ap); va_end(ap); }
-                                    main() { char b[10]; signal(SIGSEGV,segv); expand("%s", NULL); exit(0); }
+                                    #include <stdlib.h>
+                                    void segv() { exit(1); }
+                                    void expand(char *f,...) { va_list ap; char b[10]; va_start(ap,f); vsnprintf(b,10,f,ap); va_end(ap); }
+                                    int main() { char b[10]; signal(SIGSEGV,segv); expand("%s", NULL); exit(0); }
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
diff --git a/configure.ac b/configure.ac
index af173540785271fd..071933830f3676b2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -323,8 +323,9 @@ if test "x-$ac_cv_func_snprintf" = "x-yes" ; then
     AC_MSG_CHECKING([if snprintf can handle NULL arguments])
     AC_RUN_IFELSE([AC_LANG_SOURCE([[#include <stdio.h>
                                     #include <signal.h>
-                                    segv() { exit(1); }
-                                    main() { char b[10]; signal(SIGSEGV,segv); snprintf(b,10,"%s",NULL); exit(0); }]])],
+                                    #include <stdlib.h>
+                                    void segv() { exit(1); }
+                                    int main() { char b[10]; signal(SIGSEGV,segv); snprintf(b,10,"%s",NULL); exit(0); }]])],
                   AC_MSG_RESULT(yes),
                   [AC_MSG_RESULT(no)
                    AC_DEFINE(HAVE_BROKEN_SNPRINTF,1,[Define to 1 if 'snprintf' cannot handle NULL arguments.])])
@@ -334,9 +335,10 @@ if test "x-$ac_cv_func_vsnprintf" = "x-yes" ; then
     AC_RUN_IFELSE([AC_LANG_SOURCE([[#include <stdio.h>
                                     #include <signal.h>
                                     #include <stdarg.h>
-                                    segv() { exit(1); }
-                                    expand(char *f,...) { va_list ap; char b[10]; va_start(ap,f); vsnprintf(b,10,f,ap); va_end(ap); }
-                                    main() { char b[10]; signal(SIGSEGV,segv); expand("%s", NULL); exit(0); }]])],
+                                    #include <stdlib.h>
+                                    void segv() { exit(1); }
+                                    void expand(char *f,...) { va_list ap; char b[10]; va_start(ap,f); vsnprintf(b,10,f,ap); va_end(ap); }
+                                    int main() { char b[10]; signal(SIGSEGV,segv); expand("%s", NULL); exit(0); }]])],
                   AC_MSG_RESULT(yes),
                   [AC_MSG_RESULT(no)
                    AC_DEFINE(HAVE_BROKEN_VSNPRINTF,1,[Define to 1 if 'vsnprintf' cannot handle NULL arguments.])])
diff --git a/storage/authreg_ldapfull.c b/storage/authreg_ldapfull.c
index 6dbf202bf8627925..a545ad1dcb6cccb9 100644
--- a/storage/authreg_ldapfull.c
+++ b/storage/authreg_ldapfull.c
@@ -35,6 +35,7 @@
 #ifdef STORAGE_LDAP
 #ifdef HAVE_CRYPT
 #include <unistd.h>
+#include <crypt.h>
 #endif
 
 #ifdef HAVE_SSL
diff --git a/storage/authreg_mysql.c b/storage/authreg_mysql.c
index 0b35d6ddfd40c3af..5e15143837e66c08 100644
--- a/storage/authreg_mysql.c
+++ b/storage/authreg_mysql.c
@@ -34,6 +34,7 @@
 #else
 #ifdef HAVE_CRYPT
 #include <unistd.h>
+#include <crypt.h>
 #endif
 #endif
 
diff --git a/storage/authreg_pgsql.c b/storage/authreg_pgsql.c
index 446fa1f8217b162a..1065c5d35b629737 100644
--- a/storage/authreg_pgsql.c
+++ b/storage/authreg_pgsql.c
@@ -32,6 +32,7 @@
 #else
 #ifdef HAVE_CRYPT
 #include <unistd.h>
+#include <crypt.h>
 #endif
 #endif
 
diff --git a/storage/authreg_sqlite.c b/storage/authreg_sqlite.c
index 25058ee639238a91..dcd4cadba3504fa5 100644
--- a/storage/authreg_sqlite.c
+++ b/storage/authreg_sqlite.c
@@ -41,6 +41,7 @@
 #else
 #ifdef HAVE_CRYPT
 #include <unistd.h>
+#include <crypt.h>
 #endif
 #endif
 
diff --git a/sx/websocket.c b/sx/websocket.c
index b08e135f4966c592..4df051559850dfe1 100644
--- a/sx/websocket.c
+++ b/sx/websocket.c
@@ -22,6 +22,7 @@
  * http://tools.ietf.org/html/rfc7395
  */
 
+#define _GNU_SOURCE
 #include "sx.h"
 #include <stdarg.h>
 #include <string.h>
diff --git a/util/crypt_blowfish.h b/util/crypt_blowfish.h
index d81e8cbdea9473d0..8ba1a917a84e9276 100644
--- a/util/crypt_blowfish.h
+++ b/util/crypt_blowfish.h
@@ -23,7 +23,6 @@
 #endif
 
 extern char *bcrypt(__const char *key, __const char *setting);
-extern char *crypt_r(__const char *key, __const char *setting, void *data);
 
 #ifndef __SKIP_OW
 extern char *crypt_rn(__const char *key, __const char *setting,