Disable -faggressive-loop-optimizations in gcc 4.8+ for pre-9.2 branches.

tglsfdc · tglsfdc · commit e9e387a5b1dd · 2013-08-21T18:31:51.000-04:00
With this optimization flag enabled, recent versions of gcc can generate incorrect code that assumes variable-length arrays (such as oidvector) are actually fixed-length because they're embedded in some larger struct. The known instance of this problem was fixed in 9.2 and up by commit 8137f2c and followon work, which hides actually-variable-length catalog fields from the compiler altogether. And we plan to gradually convert variable-length fields to official "flexible array member" notation over time, which should prevent this type of bug from reappearing as gcc gets smarter. We're not going to try to back-port those changes into older branches, though, so apply this band-aid instead. Andres Freund
diff --git a/configure b/configure
@@ -4250,6 +4250,58 @@ sed 's/^/| /' conftest.$ac_ext >&5
 $as_echo "no" >&6; }
 fi
 
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+
+  # Disable loop optimizations that get confused by variable-length struct
+  # declarations in gcc 4.8+
+  { $as_echo "$as_me:$LINENO: checking if $CC supports -fno-aggressive-loop-optimizations" >&5
+$as_echo_n "checking if $CC supports -fno-aggressive-loop-optimizations... " >&6; }
+pgac_save_CFLAGS=$CFLAGS
+CFLAGS="$pgac_save_CFLAGS -fno-aggressive-loop-optimizations"
+cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext
+if { (ac_try="$ac_compile"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
+$as_echo "$ac_try_echo") >&5
+  (eval "$ac_compile") 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && {
+	 test -z "$ac_c_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest.$ac_objext; then
+  { $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	CFLAGS="$pgac_save_CFLAGS"
+                    { $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 
 elif test "$ICC" = yes; then
diff --git a/configure.in b/configure.in
@@ -435,6 +435,9 @@ if test "$GCC" = yes -a "$ICC" = no; then
   PGAC_PROG_CC_CFLAGS_OPT([-fwrapv])
   # Disable FP optimizations that cause various errors on gcc 4.5+ or maybe 4.6+
   PGAC_PROG_CC_CFLAGS_OPT([-fexcess-precision=standard])
+  # Disable loop optimizations that get confused by variable-length struct
+  # declarations in gcc 4.8+
+  PGAC_PROG_CC_CFLAGS_OPT([-fno-aggressive-loop-optimizations])
 elif test "$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.
