Re: [edk2-devel] [PATCH V2 1/2] BaseTools: Add gcc flag to warn on void* pointer arithmetic

["Leif Lindholm" <leif@nuviainc.com>]

Hi Bob,

I would say we should start by sending out an RFC set updating
tools_def.template for the various toolchains, and then make sure we
fix things in other trees (I would also like to, for example, verify
this doesn't break edk2-libc). Once other trees are cleaned up, we
can send out a PATCH and merge to master.

This is not critical for edk2-stable202008, but it is *useful*, so it
would be good if we could hit that.

/
    Leif

On Fri, Jul 24, 2020 at 03:56:25 +0000, Feng, Bob C wrote:
> What would be your suggestion on the approach to apply this build
> option to all architectures? Change the tool_def.txt firstly and
> push platform owner to fix the corresponding firmware code, or
> changing the tool_def.txt later, until this change will not break
> any platform build?
> 
> -----Original Message-----
> From: Leif Lindholm <leif@nuviainc.com> 
> Sent: Thursday, July 23, 2020 5:33 PM
> To: devel@edk2.groups.io; afish@apple.com
> Cc: Feng, Bob C <bob.c.feng@intel.com>; PierreGondois <pierre.gondois@arm.com>; Gao, Liming <liming.gao@intel.com>; tomas@nuviainc.com
> Subject: Re: [edk2-devel] [PATCH V2 1/2] BaseTools: Add gcc flag to warn on void* pointer arithmetic
> 
> Hi Andrew,
> 
> Agreed.
> 
> I also think this should be applied across all architectures, not just ARM/AARCH64. Since Visual Studio has never been been able to compile the affected code, I expect impact to Ia32/X64 to be minimal.
> 
> Regards,
> 
> Leif
> 
> On Wed, Jul 22, 2020 at 19:49:01 -0700, Andrew Fish via groups.io wrote:
> > Bob,
> > 
> > It also looks like clang could use this flag as the default seems to 
> > be to follow the GCC behavior.
> > 
> > Thanks,
> > 
> > Andrew Fish
> > 
> > > On Jul 22, 2020, at 6:56 PM, Bob Feng <bob.c.feng@intel.com> wrote:
> > > 
> > > Hi Leif
> > > 
> > > I agree to revert that patch for now and I sent a revert patch for review. After resolving the build break issue for ARM/AARCH64 platforms in edk2-platforms, and make sure there is no platform build break with this patch, we will push it again.
> > > 
> > > Thanks,
> > > Bob
> > > 
> > > -----Original Message-----
> > > From: devel@edk2.groups.io <mailto:devel@edk2.groups.io> 
> > > <devel@edk2.groups.io <mailto:devel@edk2.groups.io>> On Behalf Of 
> > > Leif Lindholm
> > > Sent: Thursday, July 23, 2020 2:06 AM
> > > To: devel@edk2.groups.io <mailto:devel@edk2.groups.io>; Feng, Bob C 
> > > <bob.c.feng@intel.com <mailto:bob.c.feng@intel.com>>
> > > Cc: PierreGondois <pierre.gondois@arm.com 
> > > <mailto:pierre.gondois@arm.com>>; Gao, Liming <liming.gao@intel.com 
> > > <mailto:liming.gao@intel.com>>; tomas@nuviainc.com 
> > > <mailto:tomas@nuviainc.com>
> > > Subject: Re: [edk2-devel] [PATCH V2 1/2] BaseTools: Add gcc flag to 
> > > warn on void* pointer arithmetic
> > > 
> > > Hi Bob,
> > > 
> > > This patch also breaks about half of the ARM/AARCH64 platforms in edk2-platforms. I agree it should go in at a later stage, but for now, can we please revert it?
> > > 
> > > Regards,
> > > 
> > > Leif
> > > 
> > > On Mon, Jul 20, 2020 at 04:10:27 +0000, Bob Feng wrote:
> > >> Reviewed-by: Bob Feng<bob.c.feng@intel.com>
> > >> 
> > >> 
> > >> -----Original Message-----
> > >> From: PierreGondois <pierre.gondois@arm.com>
> > >> Sent: Tuesday, July 7, 2020 4:35 PM
> > >> To: devel@edk2.groups.io
> > >> Cc: Pierre Gondois <Pierre.Gondois@arm.com>; Feng, Bob C 
> > >> <bob.c.feng@intel.com>; Gao, Liming <liming.gao@intel.com>; 
> > >> tomas.pilar@arm.com; nd@arm.com
> > >> Subject: [PATCH V2 1/2] BaseTools: Add gcc flag to warn on void* 
> > >> pointer arithmetic
> > >> 
> > >> From: Pierre Gondois <pierre.gondois@arm.com>
> > >> 
> > >> By default, gcc allows void* pointer arithmetic.
> > >> This is a GCC extension.
> > >> However:
> > >> - the C reference manual states that void*
> > >>   pointer "cannot be operands of addition
> > >>   or subtraction operators". Cf s5.3.1
> > >>   "Generic Pointers";
> > >> - Visual studio compiler treat such operation as
> > >>   an error.
> > >> 
> > >> To prevent such pointer arithmetic, the "-Wpointer-arith"
> > >> flag should be set for all GCC versions.
> > >> 
> > >> The "-Wpointer-arith"  allows to:
> > >>  "Warn about anything that depends on the "size of"
> > >>  a function type or of void. GNU C assigns these  types a size of 
> > >> 1, for convenience in calculations  with void * pointers and 
> > >> pointers to functions."
> > >> 
> > >> This flag is available since GCC2.95.3 which came out in 2001.
> > >> 
> > >> Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
> > >> ---
> > >> 
> > >> The changes can be seen at: 
> > >> https://github.com/PierreARM/edk2/commits/831_Add_gcc_flag_warning_
> > >> v2
> > >> 
> > >> Notes:
> > >>    v1:
> > >>     - Add "-Wpointer-arith" gcc flag. [Pierre]
> > >>    v2:
> > >>     - Only add the flag for ARM and AARCH64. [Tomas]
> > >> 
> > >> BaseTools/Conf/tools_def.template | 6 +++---
> > >> 1 file changed, 3 insertions(+), 3 deletions(-)
> > >> 
> > >> diff --git a/BaseTools/Conf/tools_def.template
> > >> b/BaseTools/Conf/tools_def.template
> > >> index
> > >> 8aeb8a2a6417e41c5660cda5066f52adc8cc3089..397b011ba38f97f81f314f864
> > >> 1ac
> > >> 8bb95d5a2197 100755
> > >> --- a/BaseTools/Conf/tools_def.template
> > >> +++ b/BaseTools/Conf/tools_def.template
> > >> @@ -1,7 +1,7 @@
> > >> #
> > >> #  Copyright (c) 2006 - 2018, Intel Corporation. All rights 
> > >> reserved.<BR>  #  Portions copyright (c) 2008 - 2009, Apple Inc. 
> > >> All rights reserved.<BR> -#  Portions copyright (c) 2011 - 2019, ARM Ltd.
> > >> All rights reserved.<BR>
> > >> +#  Portions copyright (c) 2011 - 2020, ARM Ltd. All rights 
> > >> +reserved.<BR>
> > >> #  Copyright (c) 2015, Hewlett-Packard Development Company, L.P.<BR>  #  (C) Copyright 2020, Hewlett Packard Enterprise Development LP<BR>  #  Copyright (c) Microsoft Corporation
> > >> @@ -1921,9 +1921,9 @@ NOOPT_*_*_OBJCOPY_ADDDEBUGFLAG     = --add-gnu-debuglink=$(DEBUG_DIR)/$(MODULE_N
> > >> DEFINE GCC_ALL_CC_FLAGS            = -g -Os -fshort-wchar -fno-builtin -fno-strict-aliasing -Wall -Werror -Wno-array-bounds -include AutoGen.h -fno-common
> > >> DEFINE GCC_IA32_CC_FLAGS           = DEF(GCC_ALL_CC_FLAGS) -m32 -malign-double -freorder-blocks -freorder-blocks-and-partition -O2 -mno-stack-arg-probe
> > >> DEFINE GCC_X64_CC_FLAGS            = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-address -mno-stack-arg-probe
> > >> -DEFINE GCC_ARM_CC_FLAGS            = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie
> > >> +DEFINE GCC_ARM_CC_FLAGS            = DEF(GCC_ALL_CC_FLAGS) -Wpointer-arith -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -Wno-address -mthumb -mfloat-abi=soft -fno-pic -fno-pie
> > >> DEFINE GCC_ARM_CC_XIPFLAGS         = -mno-unaligned-access
> > >> -DEFINE GCC_AARCH64_CC_FLAGS        = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char  -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic -fno-pie -ffixed-x18
> > >> +DEFINE GCC_AARCH64_CC_FLAGS        = DEF(GCC_ALL_CC_FLAGS) -Wpointer-arith -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -Wno-address -fno-asynchronous-unwind-tables -fno-unwind-tables -fno-pic -fno-pie -ffixed-x18
> > >> DEFINE GCC_AARCH64_CC_XIPFLAGS     = -mstrict-align -mgeneral-regs-only
> > >> DEFINE GCC_DLINK_FLAGS_COMMON      = -nostdlib --pie
> > >> DEFINE GCC_DLINK2_FLAGS_COMMON     = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds
> > >> --
> > >> 'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'
> > >> 
> > >> 
> > >> 
> > >> 
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