Server: Backport 0060-Check-C23-nullptr-usability-as-a-sentinel.patch

Signed-off-by: Marko Lindqvist <[email protected]>

freeciv/apply_patches.sh

@@ -30,6 +30,9 @@
 # 0049-Trigger-action-system-when-client-requests-activity-.patch
 #   Activity action fix (esp. Pillage)
 #   osdn #57670
+# 0060-Check-C23-nullptr-usability-as-a-sentinel.patch
+#   C23 compile fix
+#   RM #475
 
 # Not in the upstream Freeciv server
 # ----------------------------------
@@ -61,6 +64,7 @@ declare -a PATCHLIST=(
   "backports/0050-savegame-Fix-loading-invalid-resources-on-FoW-map"
   "backports/0054-Fix-inconsistent-city-workers-after-vision-loss"
   "backports/0049-Trigger-action-system-when-client-requests-activity-"
+  "backports/0060-Check-C23-nullptr-usability-as-a-sentinel"
   "RevertAmplio2ExtraUnits"
   "meson_webperimental"
   "metachange"

freeciv/patches/backports/0060-Check-C23-nullptr-usability-as-a-sentinel.patch

@@ -0,0 +1,74 @@
+From ac5ef97b9a6c833011278db8eeb845774062f046 Mon Sep 17 00:00:00 2001
+From: Marko Lindqvist <[email protected]>
+Date: Fri, 19 Apr 2024 17:06:10 +0300
+Subject: [PATCH 60/60] Check C23 nullptr usability as a sentinel
+
+See RM #475
+
+Signed-off-by: Marko Lindqvist <[email protected]>
+---
+ m4/c23.m4   | 21 +++++++++++++--------
+ meson.build |  9 ++++++---
+ 2 files changed, 19 insertions(+), 11 deletions(-)
+
+diff --git a/m4/c23.m4 b/m4/c23.m4
+index 0c57f04856..9a265a0065 100644
+--- a/m4/c23.m4
++++ b/m4/c23.m4
+@@ -1,18 +1,23 @@
+ # Check for the presence of C23 features.
+
+-# Check for C23 nullptr, and define FREECIV_HAVE_C23_NULLPTR if it's available
++# Check for C23 nullptr that can be passed as sentinel
++# and define FREECIV_HAVE_C23_NULLPTR if such is available
+ #
+ AC_DEFUN([FC_C23_NULLPTR],
+ [
+   AC_LANG_PUSH([C])
+-  AC_CHECK_HEADERS([stddef])
++  AC_CHECK_HEADERS([stddef.h])
+   AC_CACHE_CHECK([for C23 nullptr], [ac_cv_c23_nullptr],
+-    [AC_LINK_IFELSE([AC_LANG_PROGRAM(
+-[[#ifdef HAVE_STDDEF
+-#include <stddef>
+-#endif]],
+- [[ int *var = nullptr; ]])],
+-[ac_cv_c23_nullptr=yes], [ac_cv_c23_nullptr=no])])
++    [_cflags_="$CFLAGS"
++     CFLAGS="$EXTRA_DEBUG_CFLAGS $CFLAGS"
++     AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
++[[#ifdef HAVE_STDDEF_H
++#include <stddef.h>
++#endif
++void sentinental(...) __attribute__((__sentinel__(0)));]],
++ [[ sentinental(nullptr); ]])],
++[ac_cv_c23_nullptr=yes], [ac_cv_c23_nullptr=no])]
++  CFLAGS="$_cflags_")
+   if test "x${ac_cv_c23_nullptr}" = "xyes" ; then
+     AC_DEFINE([FREECIV_HAVE_C23_NULLPTR], [1], [C23 nullptr available])
+   fi
+diff --git a/meson.build b/meson.build
+index 0a0b904599..c6b7483303 100644
+--- a/meson.build
++++ b/meson.build
+@@ -585,11 +585,14 @@ if zstd_dep.found()
+   pub_conf_data.set('FREECIV_HAVE_LIBZSTD', 1)
+ endif
+
++# Check for c23 nullptr that can be passed as sentinel
+ if c_compiler.compiles('''
+-#include <stddef>
+-int main(void) { int *var = nullptr; return 0; }''',
++#include <stddef.h>
++void sentinental(...) __attribute__((__sentinel__(0)));
++void caller(void) { sentinental(nullptr); }''',
+   name: 'c23 nullptr',
+-  include_directories: include_directories(cross_inc_path))
++  include_directories: include_directories(cross_inc_path),
++  args: ['-Wformat'])
+   pub_conf_data.set('FREECIV_HAVE_C23_NULLPTR', 1)
+ endif
+
+-- 
+2.43.0
+