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

["Yuwei Chen" <yuwei.chen@intel.com>]

Reviewed-by: Yuwei Chen<yuwei.chen@intel.com>

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of
> PierreGondois
> 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: [edk2-devel] [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_v
> 2
> 
> 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
> 1ac8bb95d5a2197 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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