From b665c964edf64e251336449bf42c39ff61c74805 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 5 Apr 2015 13:01:55 -0400
Subject: [PATCH] Suppress clang's unhelpful gripes about -pthread switch being
 unused.

Considering the number of cases in which "unused" command line arguments
are silently ignored by compilers, it's fairly astonishing that anybody
thought this warning was useful; it's certainly nothing but an annoyance
when building Postgres.  One such case is that neither gcc nor clang
complain about unrecognized -Wno-foo switches, making it more difficult
to figure out whether the switch does anything than one could wish.

Back-patch to 9.3, which is as far back as the patch applies conveniently
(we'd have to back-patch PGAC_PROG_CC_VAR_OPT to go further, and it doesn't
seem worth that).

(cherry picked from commit 73b416b2e41237b657d29d8f42a4bb34bf700928)
(cherry picked from commit 28d6c2895fdcbdfe7d615736b8fa88240b2b89bf)
---
 configure    | 41 +++++++++++++++++++++++++++++++++++++++++
 configure.in |  7 +++++++
 2 files changed, 48 insertions(+)

diff --git a/configure b/configure
index f9900a41b9..83821c42c4 100755
--- a/configure
+++ b/configure
@@ -5518,6 +5518,47 @@ if test x"$pgac_cv_prog_cc_cflags__ftree_vectorize" = x"yes"; then
   CFLAGS_VECTOR="${CFLAGS_VECTOR} -ftree-vectorize"
 fi
 
+  # We want to suppress clang's unhelpful unused-command-line-argument warnings
+  # but gcc won't complain about unrecognized -Wno-foo switches, so we have to
+  # test for the positive form and if that works, add the negative form
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -Wunused-command-line-argument" >&5
+$as_echo_n "checking whether $CC supports -Wunused-command-line-argument... " >&6; }
+if ${pgac_cv_prog_cc_cflags__Wunused_command_line_argument+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+CFLAGS="$pgac_save_CFLAGS -Wunused-command-line-argument"
+ac_save_c_werror_flag=$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__Wunused_command_line_argument=yes
+else
+  pgac_cv_prog_cc_cflags__Wunused_command_line_argument=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"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_cc_cflags__Wunused_command_line_argument" >&5
+$as_echo "$pgac_cv_prog_cc_cflags__Wunused_command_line_argument" >&6; }
+if test x"$pgac_cv_prog_cc_cflags__Wunused_command_line_argument" = x"yes"; then
+  NOT_THE_CFLAGS="${NOT_THE_CFLAGS} -Wunused-command-line-argument"
+fi
+
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-unused-command-line-argument"
+  fi
 elif test "$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.in b/configure.in
index 16bf8a123f..0d57e9dca0 100644
--- a/configure.in
+++ b/configure.in
@@ -516,6 +516,13 @@ if test "$GCC" = yes -a "$ICC" = no; then
   # Optimization flags for specific files that benefit from vectorization
   PGAC_PROG_CC_VAR_OPT(CFLAGS_VECTOR, [-funroll-loops])
   PGAC_PROG_CC_VAR_OPT(CFLAGS_VECTOR, [-ftree-vectorize])
+  # We want to suppress clang's unhelpful unused-command-line-argument warnings
+  # but gcc won't complain about unrecognized -Wno-foo switches, so we have to
+  # test for the positive form and if that works, add the negative form
+  PGAC_PROG_CC_VAR_OPT(NOT_THE_CFLAGS, [-Wunused-command-line-argument])
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-unused-command-line-argument"
+  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.
-- 
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