From 906548689e37ab6cca1e93b3f8d9327a4e17e8af Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Thu, 4 Jan 2018 17:05:09 +0100 Subject: [PATCH] build-sys: compile with -Og or -O1 when --enable-debug MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When --enable-debug is turned on, configure doesn't set -O level, and uses default compiler -O0 level, which is slow. Instead, use -Og if supported by the compiler (optimize debugging experience), or -O1 (keeps code somewhat debuggable and works around compiler bugs). Unfortunately, gcc has many false-positive maybe-uninitialized errors with Og and O1 (f27 gcc 7.2.1 20170915): /home/elmarco/src/qemu/hw/ipmi/isa_ipmi_kcs.c: In function ‘ipmi_kcs_ioport_read’: /home/elmarco/src/qemu/hw/ipmi/isa_ipmi_kcs.c:279:12: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized] return ret; ^~~ cc1: all warnings being treated as errors make: *** [/home/elmarco/src/qemu/rules.mak:66: hw/ipmi/isa_ipmi_kcs.o] Error 1 make: *** Waiting for unfinished jobs.... /home/elmarco/src/qemu/hw/ide/ahci.c: In function ‘ahci_populate_sglist’: /home/elmarco/src/qemu/hw/ide/ahci.c:903:58: error: ‘tbl_entry_size’ may be used uninitialized in this function [-Werror=maybe-uninitialized] if ((off_idx == -1) || (off_pos < 0) || (off_pos > tbl_entry_size)) { ~~~~~~~~~^~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors make: *** [/home/elmarco/src/qemu/rules.mak:66: hw/ide/ahci.o] Error 1 /home/elmarco/src/qemu/hw/display/qxl.c: In function ‘qxl_add_memslot’: /home/elmarco/src/qemu/hw/display/qxl.c:1397:52: error: ‘pci_start’ may be used uninitialized in this function [-Werror=maybe-uninitialized] memslot.virt_end = virt_start + (guest_end - pci_start); ~~~~~~~~~~~~~^~~~~~~~~~~~ /home/elmarco/src/qemu/hw/display/qxl.c:1389:9: error: ‘pci_region’ may be used uninitialized in this function [-Werror=maybe-uninitialized] qxl_set_guest_bug(d, "%s: pci_region = %d", __func__, pci_region); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors There seems to be a long list of related bugs in upstream GCC, some of them are being fixed very recently: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639 For now, let's workaround it by using Wno-maybe-uninitialized (gcc-only). Suggested-by: Paolo Bonzini Signed-off-by: Marc-André Lureau Message-Id: <20180104160523.22995-5-marcandre.lureau@redhat.com> Tested-by: Philippe Mathieu-Daudé Signed-off-by: Paolo Bonzini --- configure | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/configure b/configure index ac392d2fda..6f1b7cd83d 100755 --- a/configure +++ b/configure @@ -5194,8 +5194,19 @@ if test "$gcov" = "yes" ; then LDFLAGS="-fprofile-arcs -ftest-coverage $LDFLAGS" elif test "$fortify_source" = "yes" ; then CFLAGS="-O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $CFLAGS" -elif test "$debug" = "no"; then - CFLAGS="-O2 $CFLAGS" +elif test "$debug" = "yes"; then + if compile_prog "-Og" ""; then + CFLAGS="-Og $CFLAGS" + elif compile_prog "-O1" ""; then + CFLAGS="-O1 $CFLAGS" + fi + # Workaround GCC false-positive Wuninitialized bugs with Og or O1: + # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=24639 + if cc_has_warning_flag "-Wno-maybe-uninitialized"; then + CFLAGS="-Wno-maybe-uninitialized $CFLAGS" + fi +else + CFLAGS="-O2 $CFLAGS" fi ##########################################