Use -Wno-format-truncation and -Wno-stringop-truncation, if available.

gcc 8 has started emitting some warnings that are largely useless for
our purposes, particularly since they complain about code following
the project-standard coding convention that path names are assumed
to be shorter than MAXPGPATH.  Even if we make the effort to remove
that assumption in some future release, the changes wouldn't get
back-patched.  Hence, just suppress these warnings, on compilers that
have these switches.

Backpatch to all supported branches.

Discussion: https://postgr.es/m/1524563856.26306.9.camel@gunduz.org

2 files changed, 92 insertions, 0 deletions

diff --git a/configure b/configure
index b37a972ee0a..2fe514fcda0 100755
--- a/configure
+++ b/configure
@@ -4833,6 +4833,7 @@ 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
+  NOT_THE_CFLAGS=""
   { $as_echo "$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 ${pgac_cv_prog_cc_cflags__Wunused_command_line_argument+:} false; then :
@@ -4871,6 +4872,85 @@ fi
   if test -n "$NOT_THE_CFLAGS"; then
     CFLAGS="$CFLAGS -Wno-unused-command-line-argument"
   fi
+  # Similarly disable useless truncation warnings from gcc 8+
+  NOT_THE_CFLAGS=""
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -Wformat-truncation" >&5
+$as_echo_n "checking whether $CC supports -Wformat-truncation... " >&6; }
+if ${pgac_cv_prog_cc_cflags__Wformat_truncation+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+CFLAGS="$pgac_save_CFLAGS -Wformat-truncation"
+ac_save_c_werror_flag=$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__Wformat_truncation=yes
+else
+  pgac_cv_prog_cc_cflags__Wformat_truncation=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: $pgac_cv_prog_cc_cflags__Wformat_truncation" >&5
+$as_echo "$pgac_cv_prog_cc_cflags__Wformat_truncation" >&6; }
+if test x"$pgac_cv_prog_cc_cflags__Wformat_truncation" = x"yes"; then
+  NOT_THE_CFLAGS="${NOT_THE_CFLAGS} -Wformat-truncation"
+fi
+
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-format-truncation"
+  fi
+  NOT_THE_CFLAGS=""
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC supports -Wstringop-truncation" >&5
+$as_echo_n "checking whether $CC supports -Wstringop-truncation... " >&6; }
+if ${pgac_cv_prog_cc_cflags__Wstringop_truncation+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+CFLAGS="$pgac_save_CFLAGS -Wstringop-truncation"
+ac_save_c_werror_flag=$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__Wstringop_truncation=yes
+else
+  pgac_cv_prog_cc_cflags__Wstringop_truncation=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: $pgac_cv_prog_cc_cflags__Wstringop_truncation" >&5
+$as_echo "$pgac_cv_prog_cc_cflags__Wstringop_truncation" >&6; }
+if test x"$pgac_cv_prog_cc_cflags__Wstringop_truncation" = x"yes"; then
+  NOT_THE_CFLAGS="${NOT_THE_CFLAGS} -Wstringop-truncation"
+fi
+
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-stringop-truncation"
+  fi
 elif test "$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 e6368292bf1..36ab6f20d07 100644
--- a/configure.in
+++ b/configure.in
@@ -468,10 +468,22 @@ if test "$GCC" = yes -a "$ICC" = no; then
   # 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
+  NOT_THE_CFLAGS=""
   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
+  # Similarly disable useless truncation warnings from gcc 8+
+  NOT_THE_CFLAGS=""
+  PGAC_PROG_CC_VAR_OPT(NOT_THE_CFLAGS, [-Wformat-truncation])
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-format-truncation"
+  fi
+  NOT_THE_CFLAGS=""
+  PGAC_PROG_CC_VAR_OPT(NOT_THE_CFLAGS, [-Wstringop-truncation])
+  if test -n "$NOT_THE_CFLAGS"; then
+    CFLAGS="$CFLAGS -Wno-stringop-truncation"
+  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.