From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Joshua Root <jmr@macports.org>
Date: Mon, 14 Dec 2020 07:56:34 +1100
Subject: [PATCH] 00410: bpo-42598: Fix implicit function declarations in
 configure

This is invalid in C99 and later and is an error with some compilers
(e.g. clang in Xcode 12), and can thus cause configure checks to
produce incorrect results.
---
 .../Build/2020-12-13-14-43-10.bpo-42598.7ipr5H.rst  |  2 ++
 configure                                           | 13 +++++++------
 configure.ac                                        | 13 +++++++------
 3 files changed, 16 insertions(+), 12 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2020-12-13-14-43-10.bpo-42598.7ipr5H.rst

diff --git a/Misc/NEWS.d/next/Build/2020-12-13-14-43-10.bpo-42598.7ipr5H.rst b/Misc/NEWS.d/next/Build/2020-12-13-14-43-10.bpo-42598.7ipr5H.rst
new file mode 100644
index 0000000000..7dafc105c4
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2020-12-13-14-43-10.bpo-42598.7ipr5H.rst
@@ -0,0 +1,2 @@
+Fix implicit function declarations in configure which could have resulted in
+incorrect configuration checks.  Patch contributed by Joshua Root.
diff --git a/configure b/configure
index 32c27a468d..68a46deef5 100755
--- a/configure
+++ b/configure
@@ -10840,10 +10840,10 @@ else
       int main() {
         pthread_attr_t attr;
         pthread_t id;
-        if (pthread_attr_init(&attr)) exit(-1);
-        if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM)) exit(-1);
-        if (pthread_create(&id, &attr, foo, NULL)) exit(-1);
-        exit(0);
+        if (pthread_attr_init(&attr)) return (-1);
+        if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM)) return (-1);
+        if (pthread_create(&id, &attr, foo, NULL)) return (-1);
+        return (0);
       }
 _ACEOF
 if ac_fn_c_try_run "$LINENO"; then :
@@ -14891,7 +14891,7 @@ else
   int main()
   {
 	/* Success: exit code 0 */
-        exit((((wchar_t) -1) < ((wchar_t) 0)) ? 0 : 1);
+        return ((((wchar_t) -1) < ((wchar_t) 0)) ? 0 : 1);
   }
 
 _ACEOF
@@ -15213,7 +15213,7 @@ else
 
 int main()
 {
-	exit(((-1)>>3 == -1) ? 0 : 1);
+	return (((-1)>>3 == -1) ? 0 : 1);
 }
 
 _ACEOF
@@ -15725,6 +15725,7 @@ else
 /* end confdefs.h.  */
 
 #include <poll.h>
+#include <unistd.h>
 
 int main()
 {
diff --git a/configure.ac b/configure.ac
index 2696661ab9..9d2ad9afba 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3188,10 +3188,10 @@ if test "$posix_threads" = "yes"; then
       int main() {
         pthread_attr_t attr;
         pthread_t id;
-        if (pthread_attr_init(&attr)) exit(-1);
-        if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM)) exit(-1);
-        if (pthread_create(&id, &attr, foo, NULL)) exit(-1);
-        exit(0);
+        if (pthread_attr_init(&attr)) return (-1);
+        if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM)) return (-1);
+        if (pthread_create(&id, &attr, foo, NULL)) return (-1);
+        return (0);
       }]])],
       [ac_cv_pthread_system_supported=yes],
       [ac_cv_pthread_system_supported=no],
@@ -4743,7 +4743,7 @@ then
   int main()
   {
 	/* Success: exit code 0 */
-        exit((((wchar_t) -1) < ((wchar_t) 0)) ? 0 : 1);
+        return ((((wchar_t) -1) < ((wchar_t) 0)) ? 0 : 1);
   }
   ]])],
   [ac_cv_wchar_t_signed=yes],
@@ -4818,7 +4818,7 @@ AC_CACHE_VAL(ac_cv_rshift_extends_sign, [
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
 int main()
 {
-	exit(((-1)>>3 == -1) ? 0 : 1);
+	return (((-1)>>3 == -1) ? 0 : 1);
 }
 ]])],
 [ac_cv_rshift_extends_sign=yes],
@@ -4970,6 +4970,7 @@ AC_MSG_CHECKING(for broken poll())
 AC_CACHE_VAL(ac_cv_broken_poll,
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <poll.h>
+#include <unistd.h>
 
 int main()
 {