From b01690ca859b5f27ece386577b7b9d9d7572b8d2 Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Mon, 12 Dec 2022 16:28:24 +1300
Subject: [PATCH] Disable clang 16's -Wcast-function-type-strict.

Clang 16 is still in development, but seawasp reveals that it has
started warning about many of our casts of function pointers.  Disable
the new warning for now, since otherwise buildfarm animal seawasp fails.

May be back-patched with other Clang/LLVM 16 changes around release
time.

Discussion: https://postgr.es/m/CA%2BhUKGJvX%2BL3aMN84ksT-cGy08VHErRNip3nV-WmTx7f6Pqhyw%40mail.gmail.com
---
 configure    | 44 ++++++++++++++++++++++++++++++++++++++++++++
 configure.ac |  6 ++++++
 meson.build  |  3 +++
 3 files changed, 53 insertions(+)

diff --git a/configure b/configure
index 62f382c1d1..5025448a05 100755
--- a/configure
+++ b/configure
@@ -6611,6 +6611,50 @@ fi
   if test -n "$NOT_THE_CFLAGS"; then
     CFLAGS="$CFLAGS -Wno-stringop-truncation"
   fi
+  # Suppress clang 16's strict warnings about function casts
+  NOT_THE_CFLAGS=""
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -Wcast-function-type-strict, for NOT_THE_CFLAGS" >&5
+$as_echo_n "checking whether ${CC} supports -Wcast-function-type-strict, for NOT_THE_CFLAGS... " >&6; }
+if ${pgac_cv_prog_CC_cflags__Wcast_function_type_strict+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+pgac_save_CC=$CC
+CC=${CC}
+CFLAGS="${NOT_THE_CFLAGS} -Wcast-function-type-strict"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_prog_CC_cflags__Wcast_function_type_strict=yes
+else
+  pgac_cv_prog_CC_cflags__Wcast_function_type_strict=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$pgac_save_CFLAGS"
+CC="$pgac_save_CC"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__Wcast_function_type_strict" >&5
+$as_echo "$pgac_cv_prog_CC_cflags__Wcast_function_type_strict" >&6; }
+if test x"$pgac_cv_prog_CC_cflags__Wcast_function_type_strict" = x"yes"; then
+  NOT_THE_CFLAGS="${NOT_THE_CFLAGS} -Wcast-function-type-strict"
+fi
+
+
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-cast-function-type-strict"
+  fi
 elif test "$ICC" = yes; then
   # Intel's compiler has a bug/misoptimization in checking for
   # division by NAN (NaN == 0), -mp1 fixes it, so add it to the CFLAGS.
diff --git a/configure.ac b/configure.ac
index cfb10f59ce..4cd328fc83 100644
--- a/configure.ac
+++ b/configure.ac
@@ -573,6 +573,12 @@ if test "$GCC" = yes -a "$ICC" = no; then
   if test -n "$NOT_THE_CFLAGS"; then
     CFLAGS="$CFLAGS -Wno-stringop-truncation"
   fi
+  # Suppress clang 16's strict warnings about function casts
+  NOT_THE_CFLAGS=""
+  PGAC_PROG_CC_VAR_OPT(NOT_THE_CFLAGS, [-Wcast-function-type-strict])
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-cast-function-type-strict"
+  fi
 elif test "$ICC" = yes; then
   # Intel's compiler has a bug/misoptimization in checking for
   # division by NAN (NaN == 0), -mp1 fixes it, so add it to the CFLAGS.
diff --git a/meson.build b/meson.build
index a62d8171cc..9df8685dfd 100644
--- a/meson.build
+++ b/meson.build
@@ -1773,6 +1773,9 @@ negative_warning_flags = [
   'format-truncation',
   'stringop-truncation',
 
+  # Suppress clang 16's strict warnings about function casts
+  'cast-function-type-strict',
+
   # To make warning_level=2 / -Wextra work, we'd need at least the following
   # 'clobbered',
   # 'missing-field-initializers',
-- 
2.35.1