From 6ad7a7486c3f1e1b907dadd132364fa9e611ccf0 Mon Sep 17 00:00:00 2001
From: Jim DeLaHunt <from+project_by_git@jdlh.com>
Date: Sat, 29 Jan 2022 01:28:13 -0800
Subject: [PATCH] Eliminate needless -Wimplicit-function-declaration errors on
 macOS

Configuration macros FC_CHECK_X_PROTO_FUNCPROTO_COMPILE and
FC_CHECK_X_PROTO_NARROWPROTO_WORKS in m4/x.m4 generate simple C programs
to check aspects of X11 configuration. These programs fail to #include
<stdlib.h>, so their use of exit() is implicitly declared. This has been
illegal C language since the late 1980's, but tolerated by compilers.
However, since 2019, macOS compilers have raised
-Wimplicit-function-declaration errors with such constructs. They have
good reasons to do so, related to support for ARM instruction sets.

Insert `#include <stdlib.h>` into each of these two macros in m4/x.m4 .

Similarly, configuration macro FC_FUNC_VSNPRINTF in m4/vsnprintf.m4
generates a simple C program which uses exit() without #include
<stdlib.h>, and strcmp() without #include <string.h>. This also causes
the macOS compiler to raise -Wimplicit-function-declaration errors.

Insert `#include <stdlib.h>` and `#include <string.h>` into this macro
in m4/vsnprintf.m4 .

Fixes ticket #43737, "Configure scripts give needless
-Wimplicit-function-declaration errors on macOS",
https://osdn.net/projects/freeciv/ticket/43737 for more information.
---
 m4/vsnprintf.m4 | 2 ++
 m4/x.m4         | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/m4/vsnprintf.m4 b/m4/vsnprintf.m4
index 87641f7479..282172fae5 100644
--- a/m4/vsnprintf.m4
+++ b/m4/vsnprintf.m4
@@ -14,6 +14,8 @@ AC_DEFUN([FC_FUNC_VSNPRINTF],
   [ac_cv_func_working_vsnprintf],
 [AC_RUN_IFELSE([AC_LANG_SOURCE([[#include <stdio.h>
 #include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
 
 int
 doit(char * s, ...)
diff --git a/m4/x.m4 b/m4/x.m4
index 5309dfc04b..80ef46e61c 100644
--- a/m4/x.m4
+++ b/m4/x.m4
@@ -325,6 +325,7 @@ fc_x_save_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS $X_CFLAGS"
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 $fc_x_compile
+#include <stdlib.h>
 #include <X11/Xfuncproto.h>
   ]], [[
 exit (0)
@@ -374,6 +375,7 @@ CFLAGS="$CFLAGS $X_CFLAGS $X_LIBS $X_PRE_LIBS -lXaw -lXt -lX11 $X_EXTRA_LIBS"
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
 $fc_x_works
 $fc_x_compile
+#include <stdlib.h>
 #include <X11/Xfuncproto.h>
 #include <X11/Intrinsic.h>
 #include <X11/StringDefs.h>
-- 
2.35.0