Fix implicit declaration of functions.
https://bugs.php.net/bug.php?id=80171
https://github.com/php/php-src/commit/aa405b7da270595d349d0596ad31305a41d4b1c0
https://github.com/php/php-src/commit/00ba784a2ce95e009f98e0e6d263634673a3f2e1
--- a/acinclude.m4.orig	2018-12-04 11:23:01.000000000 -0600
+++ b/acinclude.m4	2020-12-30 03:58:55.000000000 -0600
@@ -1225,14 +1225,14 @@
 #include <unistd.h>
 #include <errno.h>
 $1
-    main() {
+    int main() {
     int fd = open("conftest_in", O_WRONLY|O_CREAT, 0600);
 
-    if (fd < 0) exit(1);
-    if (pwrite(fd, "text", 4, 0) != 4) exit(1);
+    if (fd < 0) return 1;
+    if (pwrite(fd, "text", 4, 0) != 4) return 1;
     /* Linux glibc breakage until 2.2.5 */
-    if (pwrite(fd, "text", 4, -1) != -1 || errno != EINVAL) exit(1);
-    exit(0);
+    if (pwrite(fd, "text", 4, -1) != -1 || errno != EINVAL) return 1;
+    return 0;
     }
 
   ],[
@@ -1255,14 +1255,14 @@
 #include <unistd.h>
 #include <errno.h>
 $1
-    main() {
+    int main() {
     char buf[3]; 
     int fd = open("conftest_in", O_RDONLY);
-    if (fd < 0) exit(1);
-    if (pread(fd, buf, 2, 0) != 2) exit(1);
+    if (fd < 0) return 1;
+    if (pread(fd, buf, 2, 0) != 2) return 1;
     /* Linux glibc breakage until 2.2.5 */
-    if (pread(fd, buf, 2, -1) != -1 || errno != EINVAL) exit(1);
-    exit(0);
+    if (pread(fd, buf, 2, -1) != -1 || errno != EINVAL) return 1;
+    return 0;
     }
   ],[
     ac_cv_pread=yes
@@ -1363,25 +1363,26 @@
 #define _REENTRANT
 #include <sys/types.h>
 #include <dirent.h>
+#include <unistd.h>
 
 #ifndef PATH_MAX
 #define PATH_MAX 1024
 #endif
 
-main() {
+int main() {
   DIR *dir;
   char entry[sizeof(struct dirent)+PATH_MAX];
   struct dirent *pentry = (struct dirent *) &entry;
 
   dir = opendir("/");
   if (!dir) 
-    exit(1);
+    return 1;
   if (readdir_r(dir, (struct dirent *) entry, &pentry) == 0) {
     close(dir);
-    exit(0);
+    return 0;
   }
   close(dir);
-  exit(1);
+  return 1;
 }
     ],[
       ac_cv_what_readdir_r=POSIX
@@ -1711,6 +1712,7 @@
   AC_CACHE_VAL(_cv_have_broken_glibc_fopen_append,[
   AC_TRY_RUN([
 #include <stdio.h>
+#include <unistd.h>
 int main(int argc, char *argv[])
 {
   FILE *fp;
@@ -1720,7 +1722,7 @@
   fp = fopen(filename, "w");
   if (fp == NULL) {
     perror("fopen");
-    exit(2);
+    return 2;
   }
   fputs("foobar", fp);
   fclose(fp);
@@ -1794,13 +1796,13 @@
 
 cookie_io_functions_t funcs = {reader, writer, seeker, closer};
 
-main() {
+int main() {
   struct cookiedata g = { 0 };
   FILE *fp = fopencookie(&g, "r", funcs);
 
   if (fp && fseek(fp, 8192, SEEK_SET) == 0 && g.pos == 8192)
-    exit(0);
-  exit(1);
+    return 0;
+  return 1;
 }
 
 ], [
--- a/build/libtool.m4.orig	2018-12-04 11:22:44.000000000 -0600
+++ b/build/libtool.m4	2020-12-30 03:57:09.000000000 -0600
@@ -978,10 +978,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -997,7 +993,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+    return status;
 }]
 EOF
   if AC_TRY_EVAL(ac_link) && test -s conftest${ac_exeext} 2>/dev/null; then
--- a/configure.orig	2018-12-04 11:22:44.000000000 -0600
+++ b/configure	2020-12-30 04:00:52.000000000 -0600
@@ -12541,13 +12529,13 @@
 
 cookie_io_functions_t funcs = {reader, writer, seeker, closer};
 
-main() {
+int main() {
   struct cookiedata g = { 0 };
   FILE *fp = fopencookie(&g, "r", funcs);
 
   if (fp && fseek(fp, 8192, SEEK_SET) == 0 && g.pos == 8192)
-    exit(0);
-  exit(1);
+    return 0;
+  return 1;
 }
 
 
@@ -12662,6 +12650,7 @@
 /* end confdefs.h.  */
 
 #include <stdio.h>
+#include <unistd.h>
 int main(int argc, char *argv[])
 {
   FILE *fp;
@@ -12671,7 +12660,7 @@
   fp = fopen(filename, "w");
   if (fp == NULL) {
     perror("fopen");
-    exit(2);
+    return 2;
   }
   fputs("foobar", fp);
   fclose(fp);
@@ -14598,6 +14587,7 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <string.h>
 #include <netdb.h>
 #include <sys/types.h>
 #ifndef AF_INET
@@ -14610,11 +14600,11 @@
   hints.ai_flags = AI_NUMERICHOST;
 
   if (getaddrinfo("127.0.0.1", 0, &hints, &ai) < 0) {
-    exit(1);
+    return 1;
   }
 
   if (ai == 0) {
-    exit(1);
+    return 1;
   }
 
   pai = ai;
@@ -14622,16 +14612,16 @@
   while (pai) {
     if (pai->ai_family != AF_INET) {
       /* 127.0.0.1/NUMERICHOST should only resolve ONE way */
-      exit(1);
+      return 1;
     }
     if (pai->ai_addr->sa_family != AF_INET) {
       /* 127.0.0.1/NUMERICHOST should only resolve ONE way */
-      exit(1);
+      return 1;
     }
     pai = pai->ai_next;
   }
   freeaddrinfo(ai);
-  exit(0);
+  return 0;
 }
 
 _ACEOF
@@ -15145,25 +15135,26 @@
 #define _REENTRANT
 #include <sys/types.h>
 #include <dirent.h>
+#include <unistd.h>
 
 #ifndef PATH_MAX
 #define PATH_MAX 1024
 #endif
 
-main() {
+int main() {
   DIR *dir;
   char entry[sizeof(struct dirent)+PATH_MAX];
   struct dirent *pentry = (struct dirent *) &entry;
 
   dir = opendir("/");
   if (!dir)
-    exit(1);
+    return 1;
   if (readdir_r(dir, (struct dirent *) entry, &pentry) == 0) {
     close(dir);
-    exit(0);
+    return 0;
   }
   close(dir);
-  exit(1);
+  return 1;
 }
 
 _ACEOF
@@ -74932,14 +74923,14 @@
 #include <unistd.h>
 #include <errno.h>
 
-    main() {
+    int main() {
     int fd = open("conftest_in", O_WRONLY|O_CREAT, 0600);
 
-    if (fd < 0) exit(1);
-    if (pwrite(fd, "text", 4, 0) != 4) exit(1);
+    if (fd < 0) return 1;
+    if (pwrite(fd, "text", 4, 0) != 4) return 1;
     /* Linux glibc breakage until 2.2.5 */
-    if (pwrite(fd, "text", 4, -1) != -1 || errno != EINVAL) exit(1);
-    exit(0);
+    if (pwrite(fd, "text", 4, -1) != -1 || errno != EINVAL) return 1;
+    return 0;
     }
 
 
@@ -74974,14 +74965,14 @@
 #include <unistd.h>
 #include <errno.h>
 ssize_t pwrite(int, void *, size_t, off64_t);
-    main() {
+    int main() {
     int fd = open("conftest_in", O_WRONLY|O_CREAT, 0600);
 
-    if (fd < 0) exit(1);
-    if (pwrite(fd, "text", 4, 0) != 4) exit(1);
+    if (fd < 0) return 1;
+    if (pwrite(fd, "text", 4, 0) != 4) return 1;
     /* Linux glibc breakage until 2.2.5 */
-    if (pwrite(fd, "text", 4, -1) != -1 || errno != EINVAL) exit(1);
-    exit(0);
+    if (pwrite(fd, "text", 4, -1) != -1 || errno != EINVAL) return 1;
+    return 0;
     }
 
 
@@ -75043,14 +75034,14 @@
 #include <unistd.h>
 #include <errno.h>
 
-    main() {
+    int main() {
     char buf[3];
     int fd = open("conftest_in", O_RDONLY);
-    if (fd < 0) exit(1);
-    if (pread(fd, buf, 2, 0) != 2) exit(1);
+    if (fd < 0) return 1;
+    if (pread(fd, buf, 2, 0) != 2) return 1;
     /* Linux glibc breakage until 2.2.5 */
-    if (pread(fd, buf, 2, -1) != -1 || errno != EINVAL) exit(1);
-    exit(0);
+    if (pread(fd, buf, 2, -1) != -1 || errno != EINVAL) return 1;
+    return 0;
     }
 
 _ACEOF
@@ -75086,14 +75077,14 @@
 #include <unistd.h>
 #include <errno.h>
 ssize_t pread(int, void *, size_t, off64_t);
-    main() {
+    int main() {
     char buf[3];
     int fd = open("conftest_in", O_RDONLY);
-    if (fd < 0) exit(1);
-    if (pread(fd, buf, 2, 0) != 2) exit(1);
+    if (fd < 0) return 1;
+    if (pread(fd, buf, 2, 0) != 2) return 1;
     /* Linux glibc breakage until 2.2.5 */
-    if (pread(fd, buf, 2, -1) != -1 || errno != EINVAL) exit(1);
-    exit(0);
+    if (pread(fd, buf, 2, -1) != -1 || errno != EINVAL) return 1;
+    return 0;
     }
 
 _ACEOF
@@ -79036,6 +79027,8 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
 int main(int argc, char **argv)
 {
@@ -79153,6 +79146,8 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <string.h>
+
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
@@ -79164,9 +79159,9 @@
 int main() {
 #if HAVE_CRYPT
 	char *encrypted = crypt("rasmuslerdorf","rl");
-	exit(!encrypted || strcmp(encrypted,"rl.3StKT.4T8M"));
+	return !encrypted || strcmp(encrypted,"rl.3StKT.4T8M");
 #else
-	exit(1);
+	return 1;
 #endif
 }
 _ACEOF
@@ -79201,6 +79196,8 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <string.h>
+
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
@@ -79212,9 +79209,9 @@
 int main() {
 #if HAVE_CRYPT
 	char *encrypted = crypt("rasmuslerdorf","_J9..rasm");
-	exit(!encrypted || strcmp(encrypted,"_J9..rasmBYk8r9AiWNc"));
+	return !encrypted || strcmp(encrypted,"_J9..rasmBYk8r9AiWNc");
 #else
-	exit(1);
+	return 1;
 #endif
 }
 _ACEOF
@@ -79249,6 +79246,8 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <string.h>
+
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
@@ -79270,9 +79269,9 @@
 	strcpy(answer,salt);
 	strcat(answer,"rISCgZzpwk3UhDidwXvin0");
 	encrypted = crypt("rasmuslerdorf",salt);
-	exit(!encrypted || strcmp(encrypted,answer));
+	return !encrypted || strcmp(encrypted,answer);
 #else
-	exit(1);
+	return 1;
 #endif
 }
 _ACEOF
@@ -79307,6 +79306,8 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <string.h>
+
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
@@ -79325,9 +79326,9 @@
 	strcpy(answer,salt);
 	strcpy(&answer[29],"nIdrcHdxcUxWomQX9j6kvERCFjTg7Ra");
 	encrypted = crypt("rasmuslerdorf",salt);
-	exit(!encrypted || strcmp(encrypted,answer));
+	return !encrypted || strcmp(encrypted,answer);
 #else
-	exit(1);
+	return 1;
 #endif
 }
 _ACEOF
@@ -79362,6 +79363,8 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <string.h>
+
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
@@ -79379,9 +79382,9 @@
 	strcpy(answer, salt);
 	strcat(answer, "EeHCRjm0bljalWuALHSTs1NB9ipEiLEXLhYeXdOpx22gmlmVejnVXFhd84cEKbYxCo.XuUTrW.RLraeEnsvWs/");
 	encrypted = crypt("rasmuslerdorf",salt);
-	exit(!encrypted || strcmp(encrypted,answer));
+	return !encrypted || strcmp(encrypted,answer);
 #else
-	exit(1);
+	return 1;
 #endif
 }
 _ACEOF
@@ -79416,6 +79419,8 @@
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
+#include <string.h>
+
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
@@ -79433,9 +79438,9 @@
 	strcpy(answer, salt);
 	strcat(answer, "cFAm2puLCujQ9t.0CxiFIIvFi4JyQx5UncCt/xRIX23");
 	encrypted = crypt("rasmuslerdorf",salt);
-	exit(!encrypted || strcmp(encrypted,answer));
+	return !encrypted || strcmp(encrypted,answer);
 #else
-	exit(1);
+	return 1;
 #endif
 }
 _ACEOF
@@ -95204,7 +95209,10 @@
 else
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
-main() {char buf[20];exit(sprintf(buf,"testing 123")!=11); }
+
+#include <stdio.h>
+int main() {char buf[20]; return sprintf(buf,"testing 123")!=11; }
+
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
 
@@ -95554,16 +95562,16 @@
 		double d = (double) LONG_MIN * LONG_MIN + 2e9;
 
 		if ((long) d == 2e9 && (long) -d == -2e9) {
-			exit(0);
+			return 0;
 		}
 	} else if (sizeof(long) == 8) {
 		double correct = 18e18 - ((double) LONG_MIN * -2); /* Subtract ULONG_MAX + 1 */
 
 		if ((long) 18e18 == correct) { /* On 64-bit, only check between LONG_MAX and ULONG_MAX */
-			exit(0);
+			return 0;
 		}
 	}
-	exit(1);
+	return 1;
 }
 
 _ACEOF
@@ -95649,10 +95657,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -95668,7 +95672,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+    return status;
 }
 EOF
   if { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_link\""; } >&5
@@ -95882,7 +95886,7 @@
   fprintf(fp, "%d %d\n", ZEND_MM_ALIGNMENT, zeros);
   fclose(fp);
 
-  exit(0);
+  return 0;
 }
 
 _ACEOF
@@ -95992,6 +95996,7 @@
 #include <sys/mman.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <unistd.h>
 #ifndef MAP_ANON
 # ifdef MAP_ANONYMOUS
 #  define MAP_ANON MAP_ANONYMOUS
@@ -101683,10 +101688,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -101702,7 +101703,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+    return status;
 }
 EOF
   if { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_link\""; } >&5
@@ -101783,10 +101784,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -101802,7 +101799,7 @@
   else
     puts (dlerror ());
 
-    exit (status);
+    return status;
 }
 EOF
   if { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_link\""; } >&5