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SubjectRe: [PATCH 01/10] Documentation: raise minimum supported version of GCC to 5.1
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On 9/10/2021 4:40 PM, Nick Desaulniers wrote:
> commit fad7cd3310db ("nbd: add the check to prevent overflow in
> __nbd_ioctl()")
>
> raised an issue from the fallback helpers added in
>
> commit f0907827a8a9 ("compiler.h: enable builtin overflow checkers and add fallback code")
>
> Specifically, the helpers for checking whether the results of a
> multiplication overflowed (__unsigned_mul_overflow,
> __signed_add_overflow) use the division operator when
> !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW. This is problematic for 64b
> operands on 32b hosts.

"hosts" -> "targets" or "architectures"?

It might be worth putting the error that Stephen found here?

> Also, because the macro is type agnostic, it is very difficult to write
> a similarly type generic macro that dispatches to one of:
> * div64_s64
> * div64_u64
> * div_s64
> * div_u64
>
> Raising the minimum supported versions allows us to remove all of the
> fallback helpers for !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW, instead
> dispatching the compiler builtins.
>
> arm64 has already raised the minimum supported GCC version to 5.1, do
> this for all targets now. See the link below for the previous
> discussion.
>
> Link: https://lore.kernel.org/all/20210909182525.372ee687@canb.auug.org.au/
> Link: https://lore.kernel.org/lkml/CAK7LNASs6dvU6D3jL2GG3jW58fXfaj6VNOe55NJnTB8UPuk2pA@mail.gmail.com/
> Link: https://github.com/ClangBuiltLinux/linux/issues/1438
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
> Documentation/process/changes.rst | 2 +-
> scripts/min-tool-version.sh | 8 +-------
> 2 files changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
> index d3a8557b66a1..e35ab74a0f80 100644
> --- a/Documentation/process/changes.rst
> +++ b/Documentation/process/changes.rst
> @@ -29,7 +29,7 @@ you probably needn't concern yourself with pcmciautils.
> ====================== =============== ========================================
> Program Minimal version Command to check the version
> ====================== =============== ========================================
> -GNU C 4.9 gcc --version
> +GNU C 5.1 gcc --version
> Clang/LLVM (optional) 10.0.1 clang --version
> GNU make 3.81 make --version
> binutils 2.23 ld -v
> diff --git a/scripts/min-tool-version.sh b/scripts/min-tool-version.sh
> index 319f92104f56..4edc708baa63 100755
> --- a/scripts/min-tool-version.sh
> +++ b/scripts/min-tool-version.sh
> @@ -17,13 +17,7 @@ binutils)
> echo 2.23.0
> ;;
> gcc)
> - # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293
> - # https://lore.kernel.org/r/20210107111841.GN1551@shell.armlinux.org.uk
> - if [ "$SRCARCH" = arm64 ]; then
> - echo 5.1.0
> - else
> - echo 4.9.0
> - fi
> + echo 5.1.0
> ;;
> icc)
> # temporary
>

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