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Date: Tue, 16 Apr 2024 05:38:19 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: open list <linux-kernel@vger.kernel.org>, lkft-triage@lists.linaro.org,
        Linux Regressions <regressions@lists.linux.dev>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>,
        Anders Roxell <anders.roxell@linaro.org>,
        Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
        clang-built-linux <llvm@lists.linux.dev>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nathan Chancellor <nathan@kernel.org>, Jeff Xu <jeffxu@chromium.org>,
        "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
        Dan Carpenter <dan.carpenter@linaro.org>
Subject: Re: powerpc: io-defs.h:43:1: error: performing pointer arithmetic on a null pointer has undefined behavior [-Werror,-Wnull-pointer-arithmetic]
Message-ID: <20240416103819.GQ19790@gate.crashing.org>
References: <CA+G9fYtEh8zmq8k8wE-8RZwW-Qr927RLTn+KqGnq1F=ptaaNsA@mail.gmail.com>
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On Tue, Apr 16, 2024 at 03:02:52PM +0530, Naresh Kamboju wrote:
> In file included from arch/powerpc/include/asm/io.h:672:
> arch/powerpc/include/asm/io-defs.h:43:1: error: performing pointer
> arithmetic on a null pointer has undefined behavior
> [-Werror,-Wnull-pointer-arithmetic]

It is not UB, but just undefined: the program is meaningless.

It is not a null pointer but even a null pointer constant here.  It
matters in places, including here.

It would help if the warnings were more correct :-(


Segher