From 3dcdbdeb4833e45430ccc9cb3432f779a6fd8c94 Mon Sep 17 00:00:00 2001
From: "Miss Islington (bot)"
 <31488909+miss-islington@users.noreply.github.com>
Date: Sun, 13 Dec 2020 14:01:00 -0800
Subject: [PATCH] bpo-42598: Fix implicit function declarations in configure
 (GH-23690) (GH-23756)

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.
(cherry picked from commit 674fa0a740151e0416c9383f127b16014e805990)

Co-authored-by: Joshua Root <jmr@macports.org>
---
 .../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 00000000000000..7dafc105c45ea9
--- /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 2d379feb4b7bf0..ed969c55b35ab6 100755
--- a/configure
+++ b/configure
@@ -11072,10 +11072,10 @@ else
       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 :
@@ -15083,7 +15083,7 @@ 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
@@ -15464,7 +15464,7 @@ else
 
 int main()
 {
-	exit(((-1)>>3 == -1) ? 0 : 1);
+	return (((-1)>>3 == -1) ? 0 : 1);
 }
 
 _ACEOF
@@ -15934,6 +15934,7 @@ else
 /* end confdefs.h.  */
 
 #include <poll.h>
+#include <unistd.h>
 
 int main()
 {
diff --git a/configure.ac b/configure.ac
index c968d149c22d44..c74e348e077fb7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3313,10 +3313,10 @@ if test "$posix_threads" = "yes"; then
       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],
@@ -4725,7 +4725,7 @@ 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],
@@ -4847,7 +4847,7 @@ 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],
@@ -4994,6 +4994,7 @@ 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()
 {