Fixed main() prototypes in auto tests.

Future releases of GCC are planning to remove[0] default support for
some old features that were removed from C99 but GCC still accepts.

We can test for these changes by using the following -Werror=
directives

  -Werror=implicit-int
  -Werror=implicit-function-declaration
  -Werror=int-conversion
  -Werror=strict-prototypes
  -Werror=old-style-definition

Doing so revealed an issue with the auto/ tests in that the test
programs always define main as

  int main()

rather than

  int main(void)

which results in a bunch of errors like

build/autotest.c:3:23: error: function declaration isn't a prototype [-Werror=strict-prototypes]
    3 |                   int main() {
      |                       ^~~~
build/autotest.c: In function 'main':
build/autotest.c:3:23: error: old-style function definition [-Werror=old-style-definition]

The fix was easy, it only required fixing the main prototype with

  find -type f -exec sed -i 's/int main() {/int main(void) {/g' {} \;

Regardless of these upcoming GCC changes, this is probably a good thing
to do anyway for correctness.

[0]: https://fedoraproject.org/wiki/Changes/PortingToModernC

Link: <https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/CJXKTLXJUPZ4F2C2VQOTNMEA5JAUPMBD/>
Link: <https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/6SGHPHPAXKCVJ6PUZ57WVDQ5TDBVIRMF/>
Reviewed-by: Alejandro Colomar <alx@nginx.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

22 files changed, 129 insertions, 129 deletions

diff --git a/auto/atomic b/auto/atomic
index 31259fc5..f99adf7e 100644
--- a/auto/atomic
+++ b/auto/atomic
@@ -10,7 +10,7 @@ nxt_feature_name=NXT_HAVE_GCC_ATOMIC
 nxt_feature_run=yes
 nxt_feature_incs=
 nxt_feature_libs=
-nxt_feature_test="int main() {
+nxt_feature_test="int main(void) {
                       long  n = 0;
 
                       if (!__sync_bool_compare_and_swap(&n, 0, 3))
@@ -44,7 +44,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=
     nxt_feature_test="#include <atomic.h>
 
-                      int main() {
+                      int main(void) {
                           ulong_t  n = 0;
 
                           if (atomic_cas_ulong(&n, 0, 3) != 0)
@@ -70,7 +70,7 @@ fi
 if [ $nxt_found = no ]; then
 
     if [ $NXT_64BIT = 1 ]; then
-        nxt_feature_test="int main() {
+        nxt_feature_test="int main(void) {
                               long  n = 0;
                               long  o = 0;
 
@@ -87,7 +87,7 @@ if [ $nxt_found = no ]; then
                               return 0;
                           }"
     else
-        nxt_feature_test="int main() {
+        nxt_feature_test="int main(void) {
                               int  n = 0;
                               int  o = 0;
 
diff --git a/auto/capability b/auto/capability
index 48777665..c0410b34 100644
--- a/auto/capability
+++ b/auto/capability
@@ -10,7 +10,7 @@ nxt_feature_test="#include <linux/capability.h>
                   #include <unistd.h>
                   #include <sys/syscall.h>
 
-                  int main() {
+                  int main(void) {
                       struct __user_cap_header_struct hdr;
                       hdr.version = _LINUX_CAPABILITY_VERSION;
                       syscall(SYS_capget, &hdr, 0);
diff --git a/auto/clang b/auto/clang
index 1a05b5a3..975a6468 100644
--- a/auto/clang
+++ b/auto/clang
@@ -14,7 +14,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
                   #define set(dummy, ...)  sprintf(__VA_ARGS__)
 
-                  int main() {
+                  int main(void) {
                       char  buf[4];
 
                       buf[0] = '0';
@@ -37,7 +37,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_test="#include <stdio.h>
                       #define set(dummy, args...)  sprintf(args)
 
-                      int main() {
+                      int main(void) {
                           char  buf[4];
 
                           buf[0] = '0';
@@ -70,7 +70,7 @@ nxt_feature_name=NXT_HAVE_BUILTIN_UNREACHABLE
 nxt_feature_run=no
 nxt_feature_incs=
 nxt_feature_libs=
-nxt_feature_test="int main() {
+nxt_feature_test="int main(void) {
                       __builtin_unreachable();
                   }"
 . auto/feature
@@ -81,7 +81,7 @@ nxt_feature_name=NXT_HAVE_BUILTIN_PREFETCH
 nxt_feature_run=no
 nxt_feature_incs=
 nxt_feature_libs=
-nxt_feature_test="int main() {
+nxt_feature_test="int main(void) {
                       __builtin_prefetch(0);
                       return 0;
                   }"
@@ -93,7 +93,7 @@ nxt_feature_name=NXT_HAVE_BUILTIN_CLZ
 nxt_feature_run=
 nxt_feature_incs=
 nxt_feature_libs=
-nxt_feature_test="int main() {
+nxt_feature_test="int main(void) {
                       if (__builtin_clz(1) == 31)
                           return 0;
                       return 1;
@@ -106,7 +106,7 @@ nxt_feature_name=NXT_HAVE_BUILTIN_POPCOUNT
 nxt_feature_run=
 nxt_feature_incs=
 nxt_feature_libs=
-nxt_feature_test="int main() {
+nxt_feature_test="int main(void) {
                       if (__builtin_popcount(5) == 2)
                           return 0;
                       return 1;
@@ -121,7 +121,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="int n __attribute__ ((visibility(\"default\")));
 
-                  int main() {
+                  int main(void) {
                       return 1;
                   }"
 . auto/feature
@@ -134,7 +134,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="int n __attribute__ ((aligned(64)));
 
-                  int main() {
+                  int main(void) {
                       return 1;
                   }"
 . auto/feature
@@ -153,7 +153,7 @@ nxt_feature_test="#include <stdlib.h>
                       return malloc(1);
                   }
 
-                  int main() {
+                  int main(void) {
                       if (f() != NULL) {
                           return 1;
                       }
@@ -172,7 +172,7 @@ nxt_feature_test="struct s {
                       int i;
                   } __attribute__ ((__packed__));
 
-                  int main() {
+                  int main(void) {
                       return 1;
                   }"
 . auto/feature
diff --git a/auto/events b/auto/events
index 700dc20c..1ca6e7cd 100644
--- a/auto/events
+++ b/auto/events
@@ -13,7 +13,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <sys/epoll.h>
                   #include <unistd.h>
 
-                  int main() {
+                  int main(void) {
                       int  n;
 
                       n = epoll_create(1);
@@ -34,7 +34,7 @@ if [ $nxt_found = yes ]; then
                       #include <sys/signalfd.h>
                       #include <unistd.h>
 
-                      int main() {
+                      int main(void) {
                           int       n;
                           sigset_t  mask;
 
@@ -54,7 +54,7 @@ if [ $nxt_found = yes ]; then
     nxt_feature_test="#include <sys/eventfd.h>
                       #include <unistd.h>
 
-                      int main() {
+                      int main(void) {
                           int  n;
 
                           n = eventfd(0, 0);
@@ -79,7 +79,7 @@ nxt_feature_test="#include <sys/types.h>
                   #include <sys/event.h>
                   #include <unistd.h>
 
-                  int main() {
+                  int main(void) {
                       int  n;
 
                       n = kqueue();
@@ -100,7 +100,7 @@ if [ $nxt_found = yes ]; then
                       #include <sys/types.h>
                       #include <sys/event.h>
 
-                      int main() {
+                      int main(void) {
                           struct kevent  kev;
 
                           kev.filter = EVFILT_USER;
@@ -124,7 +124,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <port.h>
                   #include <unistd.h>
 
-                  int main() {
+                  int main(void) {
                       int  n;
 
                       n = port_create();
@@ -152,7 +152,7 @@ nxt_feature_test="#include <fcntl.h>
                   #include <sys/devpoll.h>
                   #include <unistd.h>
 
-                  int main() {
+                  int main(void) {
                       int  n;
 
                       n = open(\"/dev/poll\", O_RDWR);
@@ -180,7 +180,7 @@ nxt_feature_test="#include <fcntl.h>
                   #include <sys/pollset.h>
                   #include <unistd.h>
 
-                  int main() {
+                  int main(void) {
                       pollset_t  n;
 
                       n = pollset_create(-1);
diff --git a/auto/files b/auto/files
index 591c5ee1..1fa6ca28 100644
--- a/auto/files
+++ b/auto/files
@@ -12,7 +12,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <fcntl.h>
 
-                  int main() {
+                  int main(void) {
                       (void) posix_fadvise(0, 0, 0, POSIX_FADV_WILLNEED);
                       return 0;
                   }"
@@ -28,7 +28,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <fcntl.h>
 
-                  int main() {
+                  int main(void) {
                       (void) fcntl(0, F_READAHEAD, 1024);
                       return 0;
                   }"
@@ -44,7 +44,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <fcntl.h>
 
-                  int main() {
+                  int main(void) {
                       (void) fcntl(0, F_RDAHEAD, 1);
                       return 0;
                   }"
@@ -62,7 +62,7 @@ nxt_feature_test="#include <fcntl.h>
                   #include <linux/openat2.h>
                   #include <string.h>
 
-                  int main() {
+                  int main(void) {
                       struct open_how  how;
 
                       memset(&how, 0, sizeof(how));
diff --git a/auto/isolation b/auto/isolation
index 384f7ef1..cbf42d9d 100644
--- a/auto/isolation
+++ b/auto/isolation
@@ -20,7 +20,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <sys/wait.h>
                   #include <sys/syscall.h>
 
-                  int main() {
+                  int main(void) {
                       return SYS_clone | SIGCHLD;
                   }"
 . auto/feature
@@ -40,7 +40,7 @@ if [ $nxt_found = yes ]; then
                           #include <sys/syscall.h>
                           #include <sched.h>
 
-                          int main() {
+                          int main(void) {
                               return CLONE_NEW$flag;
                          }"
         . auto/feature
@@ -70,7 +70,7 @@ nxt_feature_test="#include <sys/syscall.h>
                   # error
                   #endif
 
-                  int main() {
+                  int main(void) {
                       return SYS_pivot_root;
                   }"
 . auto/feature
@@ -96,7 +96,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <sys/prctl.h>
 
-                  int main() {
+                  int main(void) {
                       return PR_SET_NO_NEW_PRIVS;
                   }"
 . auto/feature
@@ -109,7 +109,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <sys/mount.h>
 
-                  int main() {
+                  int main(void) {
                       return mount(\"/\", \"/\", \"bind\",
                                    MS_BIND | MS_REC, \"\");
                   }"
@@ -128,7 +128,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=
     nxt_feature_test="#include <sys/mount.h>
 
-                    int main() {
+                    int main(void) {
                         return nmount((void *)0, 0, 0);
                     }"
     . auto/feature
@@ -146,7 +146,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <sys/mount.h>
 
-                  int main() {
+                  int main(void) {
                       return umount2((void *)0, 0);
                   }"
 . auto/feature
@@ -163,7 +163,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=
     nxt_feature_test="#include <sys/mount.h>
 
-                    int main() {
+                    int main(void) {
                         return unmount((void *)0, 0);
                     }"
     . auto/feature
diff --git a/auto/malloc b/auto/malloc
index 06a16b54..cf6fc59e 100644
--- a/auto/malloc
+++ b/auto/malloc
@@ -13,7 +13,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
 
-                  int main() {
+                  int main(void) {
                       void  *p;
 
                       if (posix_memalign(&p, 4096, 4096) != 0)
@@ -36,7 +36,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=
     nxt_feature_test="#include <stdlib.h>
 
-                      int main() {
+                      int main(void) {
                           void  *p;
 
                           p = memalign(4096, 4096);
@@ -59,7 +59,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <malloc.h>
 
-                  int main() {
+                  int main(void) {
                       void  *p;
 
                       p = malloc(4096);
@@ -82,7 +82,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_test="#include <stdlib.h>
                       #include <malloc_np.h>
 
-                      int main() {
+                      int main(void) {
                           void  *p;
 
                           p = malloc(4096);
@@ -105,7 +105,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=
     nxt_feature_test="#include <malloc/malloc.h>
 
-                      int main() {
+                      int main(void) {
                           if (malloc_good_size(4096) < 4096)
                               return 1;
                           return 0;
@@ -125,7 +125,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
 
-                  int main() {
+                  int main(void) {
                       void  *p;
 
                       p = alloca(256);
@@ -147,7 +147,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=
     nxt_feature_test="#include <alloca.h>
 
-                      int main() {
+                      int main(void) {
                           void  *p;
 
                           p = alloca(256);
@@ -168,7 +168,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <malloc.h>
 
-                  int main() {
+                  int main(void) {
                       mallopt(M_PERTURB, 0x55);
                       return 0;
                   }"
diff --git a/auto/mmap b/auto/mmap
index 8ecdf670..e8ffac78 100644
--- a/auto/mmap
+++ b/auto/mmap
@@ -13,7 +13,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
                   #include <sys/mman.h>
 
-                  int main() {
+                  int main(void) {
                       if (mmap(NULL, 4096, PROT_READ | PROT_WRITE,
                                MAP_PRIVATE | MAP_ANON, -1, 0)
                             == MAP_FAILED)
@@ -35,7 +35,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_test="#include <stdlib.h>
                       #include <sys/mman.h>
 
-                      int main() {
+                      int main(void) {
                           if (mmap(NULL, 4096, PROT_READ | PROT_WRITE,
                                    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)
                                 == MAP_FAILED)
@@ -56,7 +56,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
                   #include <sys/mman.h>
 
-                  int main() {
+                  int main(void) {
                       if (mmap(NULL, 4096, PROT_READ | PROT_WRITE,
                                MAP_SHARED | MAP_POPULATE, -1, 0)
                             == MAP_FAILED)
@@ -76,7 +76,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
                   #include <sys/mman.h>
 
-                  int main() {
+                  int main(void) {
                       if (mmap(NULL, 4096, PROT_READ | PROT_WRITE,
                                MAP_PRIVATE | MAP_ANON | MAP_PREFAULT_READ,
                                -1, 0)
diff --git a/auto/modules/java b/auto/modules/java
index e8137217..691060b3 100644
--- a/auto/modules/java
+++ b/auto/modules/java
@@ -191,7 +191,7 @@ nxt_feature_libs="${NXT_JAVA_LDFLAGS}"
 nxt_feature_test="
     #include <jni.h>
 
-    int main() {
+    int main(void) {
         JNI_CreateJavaVM(NULL, NULL, NULL);
         return 0;
     }"
diff --git a/auto/modules/perl b/auto/modules/perl
index e9d7e109..2daebd0d 100644
--- a/auto/modules/perl
+++ b/auto/modules/perl
@@ -79,7 +79,7 @@ if /bin/sh -c "$NXT_PERL -MConfig -e 'print \"Perl version: \",
 
         static PerlInterpreter *my_perl;
 
-        int main() {
+        int main(void) {
             char argv[] = \"\\0-e\\00\";
             char *embedding[] = { &argv[0], &argv[1], &argv[4] };
 
@@ -124,7 +124,7 @@ nxt_feature_test="
     #include <EXTERN.h>
     #include <perl.h>
 
-    int main() {
+    int main(void) {
         printf(\"%s\", PERL_VERSION_STRING);
         return 0;
     }"
diff --git a/auto/modules/php b/auto/modules/php
index 7d224ec1..f0ecb709 100644
--- a/auto/modules/php
+++ b/auto/modules/php
@@ -131,7 +131,7 @@ nxt_feature_libs="${NXT_PHP_LIB} ${NXT_PHP_LDFLAGS}"
 nxt_feature_test="
     #include <php.h>
 
-    int main() {
+    int main(void) {
         printf(\"%s\", PHP_VERSION);
         return 0;
     }"
@@ -148,7 +148,7 @@ nxt_feature_test="
     #include <php.h>
     #include <php_main.h>
 
-    int main() {
+    int main(void) {
     #if (PHP_VERSION_ID < 80200)
         php_module_startup(NULL, NULL, 0);
     #else
@@ -176,7 +176,7 @@ nxt_feature_test="
     #include <php.h>
     #include <php_main.h>
 
-    int main() {
+    int main(void) {
         #ifndef ZTS
         #error ZTS is not defined.
         #endif
@@ -197,7 +197,7 @@ nxt_feature_test="
     #include <php.h>
     #include <php_main.h>
 
-    int main() {
+    int main(void) {
         zend_signal_startup();
         return 0;
     }"
diff --git a/auto/modules/python b/auto/modules/python
index 9be6b370..480ae1da 100644
--- a/auto/modules/python
+++ b/auto/modules/python
@@ -86,7 +86,7 @@ if /bin/sh -c "$NXT_PYTHON_CONFIG --prefix" >> $NXT_AUTOCONF_ERR 2>&1; then
     nxt_feature_test="
         #include <Python.h>
 
-        int main() {
+        int main(void) {
             Py_Initialize();
             return 0;
         }"
@@ -114,7 +114,7 @@ nxt_feature_test="
     #include <Python.h>
     #include <stdio.h>
 
-    int main() {
+    int main(void) {
         printf(\"%s\", PY_VERSION);
         return 0;
     }"
diff --git a/auto/modules/ruby b/auto/modules/ruby
index dbedfd72..7c2f0102 100644
--- a/auto/modules/ruby
+++ b/auto/modules/ruby
@@ -106,7 +106,7 @@ if /bin/sh -c "$NXT_RUBY -v" >> $NXT_AUTOCONF_ERR 2>&1; then
     nxt_feature_test="
         #include <ruby.h>
 
-        int main() {
+        int main(void) {
             static const char *argv[3] = {
                 \"NGINX_Unit\", \"-rrbconfig\",
                 \"-eprint RbConfig::CONFIG['libdir']\"
@@ -130,7 +130,7 @@ if /bin/sh -c "$NXT_RUBY -v" >> $NXT_AUTOCONF_ERR 2>&1; then
         nxt_feature_test="
             #include <ruby.h>
 
-            int main() {
+            int main(void) {
                 ruby_init();
                 return ruby_cleanup(0);
             }"
@@ -159,7 +159,7 @@ nxt_feature_test="
     #include <ruby.h>
     #include <ruby/version.h>
 
-    int main() {
+    int main(void) {
         printf(\"%s\", ruby_version);
         return 0;
     }"
diff --git a/auto/pcre b/auto/pcre
index 955e4baf..27205118 100644
--- a/auto/pcre
+++ b/auto/pcre
@@ -50,7 +50,7 @@ if [ $nxt_found = no ]; then
         nxt_feature_libs=$NXT_PCRE_LIB
         nxt_feature_test="#include <pcre.h>
 
-                          int main() {
+                          int main(void) {
                               pcre  *re;
 
                               re = pcre_compile(NULL, 0, NULL, 0, NULL);
diff --git a/auto/sendfile b/auto/sendfile
index 1c20db06..abbda6c7 100644
--- a/auto/sendfile
+++ b/auto/sendfile
@@ -17,7 +17,7 @@ nxt_feature="Linux sendfile()"
 nxt_feature_name=NXT_HAVE_LINUX_SENDFILE
 nxt_feature_test="#include <sys/sendfile.h>
 
-                  int main() {
+                  int main(void) {
                       off_t  offset;
 
                       sendfile(-1, -1, &offset, 0);
@@ -43,7 +43,7 @@ if [ $nxt_found = no ]; then
                       #include <sys/uio.h>
                       #include <stdlib.h>
 
-                      int main() {
+                      int main(void) {
                           off_t  sent;
 
                           sendfile(-1, -1, 0, 0, NULL, &sent, 0);
@@ -69,7 +69,7 @@ if [ $nxt_found = no ]; then
                       #include <sys/uio.h>
                       #include <stdlib.h>
 
-                      int main() {
+                      int main(void) {
                           off_t  sent;
 
                           sendfile(-1, -1, 0, &sent, NULL, 0);
@@ -100,7 +100,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs="-lsendfile"
     nxt_feature_test="#include <sys/sendfile.h>
 
-                      int main() {
+                      int main(void) {
                           size_t              sent;
                           struct sendfilevec  vec;
 
@@ -124,7 +124,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_name=NXT_HAVE_AIX_SEND_FILE
     nxt_feature_test="#include <sys/socket.h>
 
-                      int main() {
+                      int main(void) {
                           int              s;
                           struct sf_parms  sf_iobuf;
 
@@ -152,7 +152,7 @@ if [ $nxt_found = no ]; then
                       sbsize_t sendfile(int s, int fd, off_t offset,
                           bsize_t nbytes, const struct iovec *hdtrl, int flags);
 
-                      int main() {
+                      int main(void) {
                           sendfile(-1, -1, 0, 0, NULL, 0);
                           return 0;
                       }"
diff --git a/auto/shmem b/auto/shmem
index bfe0ee4a..c434a58f 100644
--- a/auto/shmem
+++ b/auto/shmem
@@ -18,7 +18,7 @@ nxt_feature_test="#include <sys/mman.h>
                   #include <sys/stat.h>
                   #include <sys/types.h>
 
-                  int main() {
+                  int main(void) {
                       int         ret;
                       static char name[] = \"/unit.configure\";
 
@@ -62,7 +62,7 @@ if [ $nxt_found = no ]; then
                       #include <sys/stat.h>
                       #include <sys/types.h>
 
-                      int main() {
+                      int main(void) {
                           static char name[] = \"/tmp/unit.configure\";
 
                           shm_unlink(name);
@@ -94,7 +94,7 @@ nxt_feature_test="#include <sys/mman.h>
                   #include <fcntl.h>
                   #include <sys/stat.h>
 
-                  int main() {
+                  int main(void) {
                       int fd = shm_open(SHM_ANON, O_RDWR, S_IRUSR | S_IWUSR);
                       if (fd == -1)
                           return 1;
@@ -119,7 +119,7 @@ nxt_feature_test="#include <linux/memfd.h>
                   #include <unistd.h>
                   #include <sys/syscall.h>
 
-                  int main() {
+                  int main(void) {
                       static char name[] = \"/unit.configure\";
 
                       int fd = syscall(SYS_memfd_create, name, MFD_CLOEXEC);
diff --git a/auto/sockets b/auto/sockets
index e344a3db..241b88eb 100644
--- a/auto/sockets
+++ b/auto/sockets
@@ -15,7 +15,7 @@ if [ $NXT_INET6 = YES ]; then
                       #include <sys/types.h>
                       #include <netinet/in.h>
 
-                      int main() {
+                      int main(void) {
                           struct sockaddr_in6  sin6;
 
                           sin6.sin6_family = AF_INET6;
@@ -36,7 +36,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
                   #include <sys/socket.h>
 
-                  int main() {
+                  int main(void) {
                       struct sockaddr  sa;
 
                       sa.sa_len = 0;
@@ -54,7 +54,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
                   #include <sys/socket.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(struct sockaddr));
                       return 0;
                   }"
@@ -70,7 +70,7 @@ nxt_feature_test="#include <stdio.h>
                   #include <sys/types.h>
                   #include <netinet/in.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(struct sockaddr_in));
                       return 0;
                   }"
@@ -86,7 +86,7 @@ nxt_feature_test="#include <stdio.h>
                   #include <sys/types.h>
                   #include <netinet/in.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(struct sockaddr_in6));
                       return 0;
                   }"
@@ -102,7 +102,7 @@ nxt_feature_test="#include <stdio.h>
                   #include <sys/types.h>
                   #include <sys/un.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(struct sockaddr_un));
                       return 0;
                   }"
@@ -117,7 +117,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
                   #include <sys/socket.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(struct sockaddr_storage));
                       return 0;
                   }"
@@ -132,7 +132,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
                   #include <sys/socket.h>
 
-                  int main() {
+                  int main(void) {
                       int  pair[2];
 
                       if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, pair) != 0)
@@ -150,7 +150,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
                   #include <sys/socket.h>
 
-                  int main() {
+                  int main(void) {
                       struct  msghdr  msg;
 
                       printf(\"%d\", (int) sizeof(msg.msg_control));
@@ -175,7 +175,7 @@ if [ $NXT_SYSTEM != DragonFly ]; then
     nxt_feature_test="#define _GNU_SOURCE
                       #include <sys/socket.h>
 
-                      int main() {
+                      int main(void) {
                           return SO_PASSCRED == 0;
                       }"
     . auto/feature
@@ -191,7 +191,7 @@ if [ $NXT_SYSTEM != DragonFly ]; then
                           #include <sys/socket.h>
                           #include <sys/un.h>
 
-                          int main() {
+                          int main(void) {
                               return sizeof(struct ucred);
                           }"
         . auto/feature
@@ -206,7 +206,7 @@ if [ $NXT_SYSTEM != DragonFly ]; then
     nxt_feature_test="#define _GNU_SOURCE
                       #include <sys/socket.h>
 
-                      int main() {
+                      int main(void) {
                           return sizeof(struct cmsgcred);
                       }"
     . auto/feature
@@ -220,7 +220,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <sys/filio.h>
 
-                  int main() {
+                  int main(void) {
                       return 0;
                   }"
 . auto/feature
@@ -235,7 +235,7 @@ nxt_feature_test="#include <unistd.h>
                   #include <sys/socket.h>
                   #include <sys/ioctl.h>
 
-                  int main() {
+                  int main(void) {
                       int  nb;
 
                       nb = 0;
@@ -255,7 +255,7 @@ nxt_feature_libs=
 nxt_feature_test="#define _GNU_SOURCE
                   #include <sys/socket.h>
 
-                  int main() {
+                  int main(void) {
                       socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
                       return 0;
                   }"
@@ -273,7 +273,7 @@ nxt_feature_test="#define _GNU_SOURCE
                   #include <stdlib.h>
                   #include <sys/socket.h>
 
-                  int main() {
+                  int main(void) {
                       accept4(0, NULL, NULL, SOCK_NONBLOCK);
                       return 0;
                   }"
diff --git a/auto/ssltls b/auto/ssltls
index d678ba74..6512d330 100644
--- a/auto/ssltls
+++ b/auto/ssltls
@@ -23,7 +23,7 @@ if [ $NXT_OPENSSL = YES ]; then
     nxt_feature_libs="-lssl -lcrypto"
     nxt_feature_test="#include <openssl/ssl.h>
 
-                      int main() {
+                      int main(void) {
                           SSL_library_init();
                           return 0;
                       }"
@@ -39,7 +39,7 @@ if [ $NXT_OPENSSL = YES ]; then
         nxt_feature_run=value
         nxt_feature_test="#include <openssl/ssl.h>
 
-                          int main() {
+                          int main(void) {
                               printf(\"\\\"%s\\\"\",
                                      SSLeay_version(SSLEAY_VERSION));
                               return 0;
@@ -61,7 +61,7 @@ if [ $NXT_OPENSSL = YES ]; then
     nxt_feature_libs="$NXT_OPENSSL_LIBS"
     nxt_feature_test="#include <openssl/ssl.h>
 
-                      int main() {
+                      int main(void) {
                           SSL_CONF_cmd(NULL, NULL, NULL);
                           return 0;
                       }"
@@ -75,7 +75,7 @@ if [ $NXT_OPENSSL = YES ]; then
     nxt_feature_libs="$NXT_OPENSSL_LIBS"
     nxt_feature_test="#include <openssl/ssl.h>
 
-                      int main() {
+                      int main(void) {
                           #if (OPENSSL_NO_TLSEXT)
                           #error OpenSSL: no tlsext support.
                           #else
@@ -100,7 +100,7 @@ if [ $NXT_GNUTLS = YES ]; then
         nxt_feature_libs=$NXT_GNUTLS_LIBS
         nxt_feature_test="#include <gnutls/gnutls.h>
 
-                          int main() {
+                          int main(void) {
                               gnutls_global_init();
                               gnutls_global_deinit();
                               return 0;
@@ -121,7 +121,7 @@ if [ $NXT_GNUTLS = YES ]; then
             nxt_feature_libs=$NXT_GNUTLS_LIBS
             nxt_feature_test="#include <gnutls/gnutls.h>
 
-                      int main() {
+                      int main(void) {
                           gnutls_transport_set_vec_push_function(NULL, NULL);
                           return 0;
                       }"
@@ -135,7 +135,7 @@ if [ $NXT_GNUTLS = YES ]; then
             nxt_feature_libs=$NXT_GNUTLS_LIBS
             nxt_feature_test="#include <gnutls/gnutls.h>
 
-                      int main() {
+                      int main(void) {
                           gnutls_global_set_time_function(NULL);
                           return 0;
                       }"
@@ -160,7 +160,7 @@ if [ $NXT_CYASSL = YES ]; then
     nxt_feature_libs="-lcyassl"
     nxt_feature_test="#include <cyassl/ssl.h>
 
-                      int main() {
+                      int main(void) {
                           CyaSSL_Init();
                           CyaSSL_Cleanup();
                           return 0;
@@ -191,7 +191,7 @@ if [ $NXT_POLARSSL = YES ]; then
     nxt_feature_libs="-lpolarssl"
     nxt_feature_test="#include <polarssl/ssl.h>
 
-                      int main() {
+                      int main(void) {
                           ssl_context  ssl;
                           memset(&ssl, '\0', sizeof(ssl));
                           ssl_init(&ssl);
diff --git a/auto/threads b/auto/threads
index ff33eaac..67b46690 100644
--- a/auto/threads
+++ b/auto/threads
@@ -47,7 +47,7 @@ nxt_feature_libs=$NXT_PTHREAD
 nxt_feature_test="#define _GNU_SOURCE
               #include <pthread.h>
 
-              int main() {
+              int main(void) {
                   pthread_yield();
                   return 0;
               }"
@@ -65,7 +65,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=$NXT_PTHREAD
     nxt_feature_test="#include <pthread.h>
 
-                  int main() {
+                  int main(void) {
                       pthread_yield_np();
                       return 0;
                   }"
@@ -82,7 +82,7 @@ nxt_feature_incs=
 nxt_feature_libs=$NXT_PTHREAD
 nxt_feature_test="#include <pthread.h>
 
-              int main() {
+              int main(void) {
                   pthread_spinlock_t  lock;
 
                   if (pthread_spin_init(&lock, PTHREAD_PROCESS_PRIVATE) != 0)
@@ -112,7 +112,7 @@ if [ $nxt_found = yes ]; then
 
                       pthread_spinlock_t  lock = 0;
 
-                      int main() {
+                      int main(void) {
                           if (pthread_spin_trylock(&lock) != 0)
                               return 1;
                           if (pthread_spin_unlock(&lock) != 0)
@@ -130,7 +130,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <semaphore.h>
 
-                  int main() {
+                  int main(void) {
                       sem_t            sem;
                       struct timespec  ts;
 
@@ -199,7 +199,7 @@ nxt_feature_test="#include <pthread.h>
                       return NULL;
                   }
 
-                  int main() {
+                  int main(void) {
                       void       *n;
                       pthread_t  pt;
 
@@ -227,7 +227,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_libs=$NXT_PTHREAD
     nxt_feature_test="#include <pthread.h>
 
-                      int main() {
+                      int main(void) {
                           pthread_key_t  key = -1;
 
                           if (pthread_key_create(&key, NULL))
@@ -250,7 +250,7 @@ if [ $nxt_found = no ]; then
                       #include <pthread.h>
                       #include <stdio.h>
 
-                      int main() {
+                      int main(void) {
                           printf(\"%d\", PTHREAD_KEYS_MAX);
                           return 0;
                       }"
diff --git a/auto/time b/auto/time
index 7663e62f..402a219c 100644
--- a/auto/time
+++ b/auto/time
@@ -13,7 +13,7 @@ nxt_feature_incs=
 nxt_feature_libs="-lrt"
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       struct timespec  ts;
 
                       if (clock_gettime(CLOCK_REALTIME_COARSE, &ts) == -1)
@@ -36,7 +36,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       struct timespec  ts;
 
                       if (clock_gettime(CLOCK_REALTIME_FAST, &ts) == -1)
@@ -53,7 +53,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       struct timespec  ts;
 
                       if (clock_gettime(CLOCK_REALTIME, &ts) == -1)
@@ -87,7 +87,7 @@ nxt_feature_incs=
 nxt_feature_libs="-lrt"
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       struct timespec  ts;
 
                       if (clock_gettime(CLOCK_MONOTONIC_COARSE, &ts) == -1)
@@ -110,7 +110,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       struct timespec  ts;
 
                       if (clock_gettime(CLOCK_MONOTONIC_FAST, &ts) == -1)
@@ -127,7 +127,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       struct timespec  ts;
 
                       if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1)
@@ -163,7 +163,7 @@ nxt_feature_libs="-lhg"
 nxt_feature_test="#include <stdlib.h>
                   #include <sys/mercury.h>
 
-                  int main() {
+                  int main(void) {
                       hg_gethrtime();
                       return 0;
                   }"
@@ -181,7 +181,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       time_t     t;
                       struct tm  tm;
 
@@ -199,7 +199,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       altzone = 0;
                       return 0;
                   }"
@@ -213,7 +213,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <time.h>
 
-                  int main() {
+                  int main(void) {
                       time_t     t;
                       struct tm  tm;
 
diff --git a/auto/types b/auto/types
index 91d53b6f..c0a871dd 100644
--- a/auto/types
+++ b/auto/types
@@ -18,7 +18,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(int));
                       return 0;
                   }"
@@ -32,7 +32,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(long));
                       return 0;
                   }"
@@ -46,7 +46,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(long long));
                       return 0;
                   }"
@@ -60,7 +60,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(void *));
                       return 0;
                   }"
@@ -80,7 +80,7 @@ nxt_feature_incs=
 nxt_feature_libs=
 nxt_feature_test="#include <stdio.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(size_t));
                       return 0;
                   }"
@@ -96,7 +96,7 @@ nxt_feature_test="#define _FILE_OFFSET_BITS  64
                   #include <unistd.h>
                   #include <stdio.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(off_t));
                       return 0;
                   }"
@@ -111,7 +111,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <time.h>
                   #include <stdio.h>
 
-                  int main() {
+                  int main(void) {
                       printf(\"%d\", (int) sizeof(time_t));
                       return 0;
                   }"
diff --git a/auto/unix b/auto/unix
index 45c6a139..1307bdbd 100644
--- a/auto/unix
+++ b/auto/unix
@@ -13,7 +13,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <unistd.h>
                   #include <sys/random.h>
 
-                  int main() {
+                  int main(void) {
                       char  buf[4];
 
                       if (getrandom(buf, 4, 0) < 0) {
@@ -35,7 +35,7 @@ if [ $nxt_found = no ]; then
                       #include <sys/syscall.h>
                       #include <linux/random.h>
 
-                      int main() {
+                      int main(void) {
                           char  buf[4];
 
                           if (syscall(SYS_getrandom, buf, 4, 0) < 0) {
@@ -56,7 +56,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_name=NXT_HAVE_GETENTROPY
     nxt_feature_test="#include <unistd.h>
 
-                      int main() {
+                      int main(void) {
                           char  buf[4];
 
                           if (getentropy(buf, 4) == -1) {
@@ -78,7 +78,7 @@ if [ $nxt_found = no ]; then
     nxt_feature_test="#include <unistd.h>
                       #include <sys/random.h>
 
-                      int main() {
+                      int main(void) {
                           char  buf[4];
 
                           if (getentropy(buf, 4) == -1) {
@@ -99,7 +99,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
                   #include <ucontext.h>
 
-                  int main() {
+                  int main(void) {
                       ucontext_t  uc;
 
                       if (getcontext(&uc) == 0) {
@@ -126,7 +126,7 @@ if [ $nxt_found = no ]; then
                       #include <stdlib.h>
                       #include <ucontext.h>
 
-                      int main() {
+                      int main(void) {
                           ucontext_t  uc;
 
                           if (getcontext(&uc) == 0) {
@@ -155,7 +155,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
                   #include <dlfcn.h>
 
-                  int main() {
+                  int main(void) {
                       void *h = dlopen(NULL, RTLD_NOW | RTLD_GLOBAL);
                       dlsym(h, \"\");
                       dlclose(h);
@@ -188,7 +188,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <stdlib.h>
                   #include <unistd.h>
 
-                  int main() {
+                  int main(void) {
                       setproctitle(\"%s\", \"title\");
                       return 0;
                   }"
@@ -204,7 +204,7 @@ nxt_feature_libs=
 nxt_feature_test="#include <unistd.h>
                   #include <grp.h>
 
-                  int main() {
+                  int main(void) {
                       getgrouplist(\"root\", 0, NULL, NULL);
                       return 0;
                   }"