8000 Disable -faggressive-loop-optimizations in gcc 4.8+ for pre-9.2 branc… · hackingwu/postgres@649839d · GitHub
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Disable -faggressive-loop-optimizations in gcc 4.8+ for pre-9.2 branches.
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
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‎configure

Lines changed: 62 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -4367,6 +4367,68 @@ if test x"$pgac_cv_prog_cc_cflags__fexcess_precision_standard" = x"yes"; then
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CFLAGS="$CFLAGS -fexcess-precision=standard"
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fi
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# Disable loop optimizations that get confused by variable-length struct
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# declarations in gcc 4.8+
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{ $as_echo "$as_me:$LINENO: checking whether $CC supports -fno-aggressive-loop-optimizations" >&5
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$as_echo_n "checking whether $CC supports -fno-aggressive-loop-optimizations... " >&6; }
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if test "${pgac_cv_prog_cc_cflags__fno_aggressive_loop_optimizations+set}" = set; then
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$as_echo_n "(cached) " >&6
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else
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pgac_save_CFLAGS=$CFLAGS
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CFLAGS="$pgac_save_CFLAGS -fno-aggressive-loop-optimizations"
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ac_save_c_werror_flag=$ac_c_werror_flag
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ac_c_werror_flag=yes
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cat >conftest.$ac_ext <<_ACEOF
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/* confdefs.h. */
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_ACEOF
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cat confdefs.h >>conftest.$ac_ext
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cat >>conftest.$ac_ext <<_ACEOF
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/* end confdefs.h. */
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int
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main ()
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{
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;
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return 0;
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}
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_ACEOF
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rm -f conftest.$ac_objext
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if { (ac_try="$ac_compile"
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case "(($ac_try" in
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*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
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*) ac_try_echo=$ac_try;;
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esac
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eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
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$as_echo "$ac_try_echo") >&5
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(eval "$ac_compile") 2>conftest.er1
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ac_status=$?
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grep -v '^ *+' conftest.er1 >conftest.err
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rm -f conftest.er1
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cat conftest.err >&5
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$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
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(exit $ac_status); } && {
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test -z "$ac_c_werror_flag" ||
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test ! -s conftest.err
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} && test -s conftest.$ac_objext; then
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pgac_cv_prog_cc_cflags__fno_aggressive_loop_optimizations=yes
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else
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$as_echo "$as_me: failed program was:" >&5
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sed 's/^/| /' conftest.$ac_ext >&5
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pgac_cv_prog_cc_cflags__fno_aggressive_loop_optimizations=no
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fi
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rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
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ac_c_werror_flag=$ac_save_c_werror_flag
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CFLAGS="$pgac_save_CFLAGS"
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fi
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{ $as_echo "$as_me:$LINENO: result: $pgac_cv_prog_cc_cflags__fno_aggressive_loop_optimizations" >&5
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$as_echo "$pgac_cv_prog_cc_cflags__fno_aggressive_loop_optimizations" >&6; }
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if test x"$pgac_cv_prog_cc_cflags__fno_aggressive_loop_optimizations" = x"yes"; then
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CFLAGS="$CFLAGS -fno-aggressive-loop-optimizations"
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fi
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elif test "$ICC" = yes; then
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# Intel's compiler has a bug/misoptimization in checking for
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# division by NAN (NaN == 0), -mp1 fixes it, so add it to the CFLAGS.

‎configure.in

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -438,6 +438,9 @@ if test "$GCC" = yes -a "$ICC" = no; then
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PGAC_PROG_CC_CFLAGS_OPT([-fwrapv])
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# Disable FP optimizations that cause various errors on gcc 4.5+ or maybe 4.6+
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PGAC_PROG_CC_CFLAGS_OPT([-fexcess-precision=standard])
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# Disable loop optimizations that get confused by variable-length struct
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# declarations in gcc 4.8+
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PGAC_PROG_CC_CFLAGS_OPT([-fno-aggressive-loop-optimizations])
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elif test "$ICC" = yes; then
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# Intel's compiler has a bug/misoptimization in checking for
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# division by NAN (NaN == 0), -mp1 fixes it, so add it to the CFLAGS.

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