On 09/07/17 17:04, Gao, Liming wrote:
> I suggest to also add this option in GCC49 tool chain RELEASE builds. GCC49
> can be used for GCC 4.9 or the above version. It doesn't enable LTO.
Good idea. There could be several reasons for picking GCC49; see e.g.
commit 432f1d83f77a ("OvmfPkg/build.sh: Use GCC49 toolchains with GCC
6.[0-2]", 2016-12-06).
Thomas, can you please CC Ard on v2?
Thank you!
Laszlo
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of
>> Thomas Lamprecht
>> Sent: Thursday, September 7, 2017 10:55 PM
>> To: edk2-devel@lists.01.org
>> Cc: Laszlo Ersek <ler...@redhat.com>; Gao, Liming <liming....@intel.com>
>> Subject: [edk2] [PATCH] BaseTools/GCC5: set -Wno-unused-const-variables on
>> RELEASE builds
>>
>> TianoCore BZ#700 <https://bugzilla.tianocore.org/show_bug.cgi?id=700>
>>
>> This fixes the RELEASE build of OVMF with GCC in version 6 or newer.
>> GCC 6 added the '-Wunused-const-variable' warning, which gets
>> activated by '-Wunused-variable' and has the following behavior:
>> "Warn whenever a constant static variable is unused aside from its
>> declaration" [1]
>>
>> Commit 2ad6ba80a1bd58382bde6b994070f7c01d2fb48d introduced a case
>> where exactly this happens on a RELEASE build. All uses of the static
>> const variable are located in debug code only, which gets thrown out
>> by the compiler on RELEASE builds and thus triggers the
>> unused-const-variable warning.
>>
>> There is currently no GCC 6 toolchain target defined and doing so
>> would add a lot of boilerplate code. Instead, use the fact that GCC
>> ignores unkown '-Wno-*' options:
>>
>> "[...] if the -Wno- form is used [...] no diagnostic is produced for
>> -Wno-unknown-warning unless other diagnostics are being produced"
>>
>> This behavior is available in GCC 5 [2] (and also earlier, for that
>> matter), so add the flag to the GCC5 toolchain, even if GCC 5 itself
>> does not supports it.
>>
>> Orient the changes on 20d00edf21d2 which moved the
>> '-Wno-unused-but-set-variable' flag to RELEASE builds only, as there
>> it ensure that it does not gets raised if the only usage of a
>> variable is in (then collapsed) debug code.
>>
>> [1]
>> https://gcc.gnu.org/onlinedocs/gcc-6.4.0/gcc/Warning-Options.html#index-Wunused-const-variable
>> [2] https://gcc.gnu.org/onlinedocs/gcc-5.4.0/gcc/Warning-Options.html
>>
>> Cc: Yonghong Zhu <yonghong....@intel.com>
>> Cc: Liming Gao <liming....@intel.com>
>> Cc: Laszlo Ersek <ler...@redhat.com>
>> Contributed-under: TianoCore Contribution Agreement 1.1
>> Signed-off-by: Thomas Lamprecht <t.lampre...@proxmox.com>
>> ---
>>
>> I hope I CCed the correct people and got the style right :)
>>
>> BaseTools/Conf/tools_def.template | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/BaseTools/Conf/tools_def.template
>> b/BaseTools/Conf/tools_def.template
>> index ba1d1a16de..7db7a174c3 100755
>> --- a/BaseTools/Conf/tools_def.template
>> +++ b/BaseTools/Conf/tools_def.template
>> @@ -5326,7 +5326,7 @@ RELEASE_GCC49_AARCH64_DLINK_FLAGS =
>> DEF(GCC49_AARCH64_DLINK_FLAGS)
>> DEBUG_GCC5_IA32_CC_FLAGS = DEF(GCC5_IA32_CC_FLAGS) -flto -Os
>> DEBUG_GCC5_IA32_DLINK_FLAGS = DEF(GCC5_IA32_X64_DLINK_FLAGS) -flto -Os
>> -Wl,-m,elf_i386,--oformat=elf32-i386
>>
>> -RELEASE_GCC5_IA32_CC_FLAGS = DEF(GCC5_IA32_CC_FLAGS) -flto -Os
>> -Wno-unused-but-set-variable
>> +RELEASE_GCC5_IA32_CC_FLAGS = DEF(GCC5_IA32_CC_FLAGS) -flto -Os
>> -Wno-unused-but-set-variable
>> -Wno-unused-const-variable
>> RELEASE_GCC5_IA32_DLINK_FLAGS = DEF(GCC5_IA32_X64_DLINK_FLAGS) -flto -Os
>> -Wl,-m,elf_i386,--oformat=elf32-i386
>>
>> NOOPT_GCC5_IA32_CC_FLAGS = DEF(GCC5_IA32_CC_FLAGS) -O0
>> @@ -5358,7 +5358,7 @@ RELEASE_GCC5_IA32_DLINK_FLAGS =
>> DEF(GCC5_IA32_X64_DLINK_FLAGS) -flto -Os -Wl,
>> DEBUG_GCC5_X64_CC_FLAGS = DEF(GCC5_X64_CC_FLAGS) -flto -DUSING_LTO
>> -Os
>> DEBUG_GCC5_X64_DLINK_FLAGS = DEF(GCC5_X64_DLINK_FLAGS) -flto -Os
>>
>> -RELEASE_GCC5_X64_CC_FLAGS = DEF(GCC5_X64_CC_FLAGS) -flto -DUSING_LTO
>> -Os -Wno-unused-but-set-variable
>> +RELEASE_GCC5_X64_CC_FLAGS = DEF(GCC5_X64_CC_FLAGS) -flto -DUSING_LTO
>> -Os -Wno-unused-but-set-variable
>> -Wno-unused-const-variable
>> RELEASE_GCC5_X64_DLINK_FLAGS = DEF(GCC5_X64_DLINK_FLAGS) -flto -Os
>>
>> NOOPT_GCC5_X64_CC_FLAGS = DEF(GCC5_X64_CC_FLAGS) -O0
>> @@ -5393,7 +5393,7 @@ RELEASE_GCC5_X64_DLINK_FLAGS =
>> DEF(GCC5_X64_DLINK_FLAGS) -flto -Os
>> DEBUG_GCC5_ARM_CC_FLAGS = DEF(GCC5_ARM_CC_FLAGS) -O0
>> DEBUG_GCC5_ARM_DLINK_FLAGS = DEF(GCC5_ARM_DLINK_FLAGS)
>>
>> -RELEASE_GCC5_ARM_CC_FLAGS = DEF(GCC5_ARM_CC_FLAGS) -flto
>> -Wno-unused-but-set-variable
>> +RELEASE_GCC5_ARM_CC_FLAGS = DEF(GCC5_ARM_CC_FLAGS) -flto
>> -Wno-unused-but-set-variable
>> -Wno-unused-const-variable
>> RELEASE_GCC5_ARM_DLINK_FLAGS = DEF(GCC5_ARM_DLINK_FLAGS) -flto -Os
>> -L$(WORKSPACE)/ArmPkg/Library/GccLto
>> -llto-arm -Wl,-plugin-opt=-pass-through=-llto-arm
>>
>> NOOPT_GCC5_ARM_CC_FLAGS = DEF(GCC5_ARM_CC_FLAGS) -O0
>> @@ -5428,7 +5428,7 @@ RELEASE_GCC5_ARM_DLINK_FLAGS =
>> DEF(GCC5_ARM_DLINK_FLAGS) -flto -Os -L$(WORKS
>> DEBUG_GCC5_AARCH64_DLINK_FLAGS = DEF(GCC5_AARCH64_DLINK_FLAGS) -z
>> common-page-size=0x1000
>> DEBUG_GCC5_AARCH64_DLINK_XIPFLAGS = -z common-page-size=0x20
>>
>> -RELEASE_GCC5_AARCH64_CC_FLAGS = DEF(GCC5_AARCH64_CC_FLAGS) -flto
>> -Wno-unused-but-set-variable -mcmodel=tiny
>> -fomit-frame-pointer
>> +RELEASE_GCC5_AARCH64_CC_FLAGS = DEF(GCC5_AARCH64_CC_FLAGS) -flto
>> -Wno-unused-but-set-variable
>> -Wno-unused-const-variable -mcmodel=tiny -fomit-frame-pointer
>> RELEASE_GCC5_AARCH64_DLINK_FLAGS = DEF(GCC5_AARCH64_DLINK_FLAGS) -flto -Os
>> -L$(WORKSPACE)/ArmPkg/Library/GccLto
>> -llto-aarch64 -Wl,-plugin-opt=-pass-through=-llto-aarch64
>> -Wno-lto-type-mismatch
>>
>> NOOPT_GCC5_AARCH64_CC_FLAGS = DEF(GCC5_AARCH64_CC_FLAGS) -O0
>> -mcmodel=small
>> --
>> 2.11.0
>>
>>
>> _______________________________________________
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>> edk2-devel@lists.01.org
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