Use -fwrapv in CFLAGS if we are using a version of gcc that accepts this flag.

This prevents compiler optimizations that assume overflow won't occur, which
breaks numerous overflow tests that we need to have working.  It is known
that gcc 4.3 causes problems and possible that 4.1 does.  Per my proposal
of some time ago and a recent report from Kris Jurka.

Backpatch as far as 8.0, which is as far as the patch conveniently goes.
7.x was pretty short of overflow tests anyway, so it may not matter there,
even assuming that anyone cares whether 7.x builds on recent gcc.

diff --git a/configure b/configure
index 23dc93746d0976ecf4d93a82f7707706ad97c40d..0f73a980f4b7144d417637210a16c71e6088adaa 100755 (executable)
--- a/configure
+++ b/configure
@@ -3080,6 +3080,60 @@ else
   echo "$as_me: failed program was:" >&5
 sed 's/^/| /' conftest.$ac_ext >&5
 
+CFLAGS="$pgac_save_CFLAGS"
+                    echo "$as_me:$LINENO: result: no" >&5
+echo "${ECHO_T}no" >&6
+fi
+rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
+
+  # Disable optimizations that assume no overflow; needed for gcc 4.3+
+  echo "$as_me:$LINENO: checking if $CC supports -fwrapv" >&5
+echo $ECHO_N "checking if $CC supports -fwrapv... $ECHO_C" >&6
+pgac_save_CFLAGS=$CFLAGS
+CFLAGS="$pgac_save_CFLAGS -fwrapv"
+cat >conftest.$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.$ac_objext
+if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
+  (eval $ac_compile) 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } &&
+        { ac_try='test -z "$ac_c_werror_flag"
+                        || test ! -s conftest.err'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; } &&
+        { ac_try='test -s conftest.$ac_objext'
+  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); }; }; then
+  echo "$as_me:$LINENO: result: yes" >&5
+echo "${ECHO_T}yes" >&6
+else
+  echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
 CFLAGS="$pgac_save_CFLAGS"
                     echo "$as_me:$LINENO: result: no" >&5
 echo "${ECHO_T}no" >&6

diff --git a/configure.in b/configure.in
index c4464537f1523b4cd90bc810de41a37fcc271fbf..cddcf27f36c73635363b16631752926d74985fd9 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.490.2.15 2008/02/24 05:22:11 tgl Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.490.2.16 2008/03/10 21:50:31 tgl Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -290,6 +290,8 @@ choke me
 
   # Disable strict-aliasing rules; needed for gcc 3.3+
   PGAC_PROG_CC_CFLAGS_OPT([-fno-strict-aliasing])
+  # Disable optimizations that assume no overflow; needed for gcc 4.3+
+  PGAC_PROG_CC_CFLAGS_OPT([-fwrapv])
 elif test x"${CC}" = x"xlc"; then
   # AIX xlc has to have strict aliasing turned off too
   PGAC_PROG_CC_CFLAGS_OPT([-qnoansialias])