Re: [edk2-devel] [Patch] BaseTools tools_def.template: Add back -fno-pie option in GCC49 tool chain

["Liming Gao" <liming.gao@intel.com>]

Laszlo:

> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Tuesday, February 4, 2020 8:02 PM
> To: devel@edk2.groups.io; Gao, Liming <liming.gao@intel.com>
> Cc: Feng, Bob C <bob.c.feng@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Subject: Re: [edk2-devel] [Patch] BaseTools tools_def.template: Add back -fno-pie option in GCC49 tool chain
> 
> (+Ard)
> 
> On 02/04/20 05:54, Liming Gao wrote:
> > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2502
> > This option is required to make GCC49 tool chain work with the high
> > version GCC compiler.
> >
> > Cc: Bob Feng <bob.c.feng@intel.com>
> > Signed-off-by: Liming Gao <liming.gao@intel.com>
> > ---
> >  BaseTools/Conf/tools_def.template | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
> > index feee2bbf16..d02424ae44 100755
> > --- a/BaseTools/Conf/tools_def.template
> > +++ b/BaseTools/Conf/tools_def.template
> > @@ -1974,7 +1974,7 @@ DEFINE GCC48_ARM_ASLDLINK_FLAGS      = DEF(GCC_ARM_ASLDLINK_FLAGS) -Wl,--oformat
> >  DEFINE GCC48_AARCH64_ASLDLINK_FLAGS  = DEF(GCC_AARCH64_ASLDLINK_FLAGS)
> >  DEFINE GCC48_ASLCC_FLAGS             = DEF(GCC_ASLCC_FLAGS)
> >
> > -DEFINE GCC49_IA32_CC_FLAGS           = DEF(GCC48_IA32_CC_FLAGS)
> > +DEFINE GCC49_IA32_CC_FLAGS           = DEF(GCC48_IA32_CC_FLAGS) -fno-pic -fno-pie
> >  DEFINE GCC49_X64_CC_FLAGS            = DEF(GCC48_X64_CC_FLAGS)
> >  DEFINE GCC49_IA32_X64_DLINK_COMMON   = -nostdlib -Wl,-n,-q,--gc-sections -z common-page-size=0x40
> >  DEFINE GCC49_IA32_X64_ASLDLINK_FLAGS = DEF(GCC49_IA32_X64_DLINK_COMMON) -Wl,--defsym=PECOFF_HEADER_SIZE=0
> DEF(GCC_DLINK2_FLAGS_COMMON) -Wl,--entry,ReferenceAcpiTable -u ReferenceAcpiTable
> > @@ -1997,7 +1997,7 @@ DEFINE GCC49_ARM_ASLDLINK_FLAGS      = DEF(GCC48_ARM_ASLDLINK_FLAGS)
> >  DEFINE GCC49_AARCH64_ASLDLINK_FLAGS  = DEF(GCC48_AARCH64_ASLDLINK_FLAGS)
> >  DEFINE GCC49_ASLCC_FLAGS             = DEF(GCC48_ASLCC_FLAGS)
> >
> > -DEFINE GCC5_IA32_CC_FLAGS            = DEF(GCC49_IA32_CC_FLAGS) -fno-pic -fno-pie
> > +DEFINE GCC5_IA32_CC_FLAGS            = DEF(GCC49_IA32_CC_FLAGS)
> >  DEFINE GCC5_X64_CC_FLAGS             = DEF(GCC49_X64_CC_FLAGS)
> >  DEFINE GCC5_IA32_X64_DLINK_COMMON    = DEF(GCC49_IA32_X64_DLINK_COMMON)
> >  DEFINE GCC5_IA32_X64_ASLDLINK_FLAGS  = DEF(GCC49_IA32_X64_ASLDLINK_FLAGS)
> >
> 
> - What has changed relative to commit 11d0cd23dd1b ("BaseTools/tools_def
> IA32: drop -no-pie linker option for GCC49", 2018-06-18)?
> 
> - Also, if we are reverting one half of 11d0cd23dd1b (the compiler
> flags), shouldn't we then revert the other half too (the linker flags)?

Yes. Half change is revert. CC_FLAGS is added back. DLINK flag is not,
because GCC4.9 doesn't know the link option -no-pie. But, GCC 4.9 accepts the CC option -fno-pie.
I verify this change. CC flags -fno-pie can resolve the build failure with GCC7.4. I also see -fno-pie option 
Is in GCC ARM and AARCH64 arch. So, I think this change is enough. 

> 
> - The commit message says, "work with the high version GCC compiler".
> What does that mean? If it is 4.9.x, with x>2, then I agree the patch is
> justified (because commit 11d0cd23dd1b was apparently made for 4.9.2).
> But if the phrase stands for gcc8 or so (just an example), then I don't
> think the patch is a good idea; users of gcc8 can just specify the GCC5
> toolchain.
> 
> Ah, indeed, I need only look at TianoCore#2502:
> 
> "GCC49 tool chain meets with the build failure when GCC7.4 compiler".
> 
> So I think this approach is wrong. Unless there is a new gcc-4.9.x
> release, i.e., after gcc-4.9.2, I think we still need commit
> 11d0cd23dd1b in place. And, please use GCC5 for gcc-7.4 -- is there a
> problem with that?

By design, GCC49 can work with the high version GCC compiler like GCC5. 
GCC49 is the tool chain without LTO enable. GCC5 is the tool chain with LTO. 
So, they are for two different GCC setting. They should both support 
high version GCC compiler. GCC49 supported GCC compiler version is from GCC 4.9.
GCC5 supported GCC compiler version is from GCC 5.0. I know GCC49 or GCC5 tool chain 
name brings a little confuse. I will add more detail info in tools_def.txt for them. 

Thanks
Liming
> 
> Thanks
> Laszlo