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Subject: Re: [PATCH] lib/mpi: Fix unused variable warnings
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     "David S. Miller" <davem@davemloft.net>,
        David Howells <dhowells@redhat.com>,
        Eric Biggers <ebiggers@google.com>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Stephan Mueller <smueller@chronox.de>,
        Marcelo Henrique Cerri <marcelo.cerri@canonical.com>,
        "Steven Rostedt (VMware)" <rostedt@goodmis.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Brendan Higgins <brendanhiggins@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Waiman Long <longman@redhat.com>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        Colin Ian King <colin.king@canonical.com>,
        Tushar Sugandhi <tusharsu@linux.microsoft.com>,
        Vitaly Chikunov <vt@altlinux.org>,
        Gilad Ben-Yossef <gilad@benyossef.com>,
        Pascal van Leeuwen <pvanleeuwen@rambus.com>,
        linux-crypto@vger.kernel.org, keyrings@vger.kernel.org,
        linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Xufeng Zhang <yunbo.xufeng@linux.alibaba.com>,
        Jia Zhang <zhang.jia@linux.alibaba.com>
References: <20200920162103.83197-1-tianjia.zhang@linux.alibaba.com>
 <20200920162103.83197-3-tianjia.zhang@linux.alibaba.com>
 <20200925081955.GV6381@gondor.apana.org.au>
From:   Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Message-ID: <c14352da-bc82-3401-755d-f618ca908f84@linux.alibaba.com>
Date:   Fri, 25 Sep 2020 17:59:51 +0800
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Hi Herbert,

Thanks for your patch, I will do a test later.

By the way, did you add special compilation parameters? I compile 
normally without warnings in gcc 6.5 and 9.3.

Best regards,
Tianjia

On 9/25/20 4:19 PM, Herbert Xu wrote:
> On Mon, Sep 21, 2020 at 12:20:55AM +0800, Tianjia Zhang wrote:
>> Expand the mpi library based on libgcrypt, and the ECC algorithm of
>> mpi based on libgcrypt requires these functions.
>> Some other algorithms will be developed based on mpi ecc, such as SM2.
>>
>> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
>> Tested-by: Xufeng Zhang <yunbo.xufeng@linux.alibaba.com>
> 
> This creates some compiler warnings.
> 
> ---8<---
> This patch removes a number of unused variables and marks others
> as unused in order to silence compiler warnings about them.
> 
> Fixes: a8ea8bdd9df9 ("lib/mpi: Extend the MPI library")
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 
> diff --git a/lib/mpi/mpi-div.c b/lib/mpi/mpi-div.c
> index 21332dab97d4..45beab8b9e9e 100644
> --- a/lib/mpi/mpi-div.c
> +++ b/lib/mpi/mpi-div.c
> @@ -92,7 +92,6 @@ void mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den)
>   	unsigned int normalization_steps;
>   	mpi_limb_t q_limb;
>   	mpi_ptr_t marker[5];
> -	unsigned int marker_nlimbs[5];
>   	int markidx = 0;
>   
>   	/* Ensure space is enough for quotient and remainder.
> @@ -152,7 +151,6 @@ void mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den)
>   		 * numerator would be gradually overwritten by the quotient limbs.
>   		 */
>   		if (qp == np) { /* Copy NP object to temporary space.  */
> -			marker_nlimbs[markidx] = nsize;
>   			np = marker[markidx++] = mpi_alloc_limb_space(nsize);
>   			MPN_COPY(np, qp, nsize);
>   		}
> @@ -173,7 +171,6 @@ void mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den)
>   		 * the most significant word.  Use temporary storage not to clobber
>   		 * the original contents of the denominator.
>   		 */
> -		marker_nlimbs[markidx] = dsize;
>   		tp = marker[markidx++] = mpi_alloc_limb_space(dsize);
>   		mpihelp_lshift(tp, dp, dsize, normalization_steps);
>   		dp = tp;
> @@ -195,7 +192,6 @@ void mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den)
>   		if (dp == rp || (quot && (dp == qp))) {
>   			mpi_ptr_t tp;
>   
> -			marker_nlimbs[markidx] = dsize;
>   			tp = marker[markidx++] = mpi_alloc_limb_space(dsize);
>   			MPN_COPY(tp, dp, dsize);
>   			dp = tp;
> diff --git a/lib/mpi/mpi-internal.h b/lib/mpi/mpi-internal.h
> index d29c4537c3a3..554002182db1 100644
> --- a/lib/mpi/mpi-internal.h
> +++ b/lib/mpi/mpi-internal.h
> @@ -114,7 +114,7 @@ typedef int mpi_size_t;		/* (must be a signed type) */
>    */
>   #define UDIV_QRNND_PREINV(q, r, nh, nl, d, di)				\
>   	do {								\
> -		mpi_limb_t _ql;						\
> +		mpi_limb_t _ql __maybe_unused;				\
>   		mpi_limb_t _q, _r;					\
>   		mpi_limb_t _xh, _xl;					\
>   		umul_ppmm(_q, _ql, (nh), (di));				\
> diff --git a/lib/mpi/mpi-mul.c b/lib/mpi/mpi-mul.c
> index 587e6335cc12..8f5fa200f297 100644
> --- a/lib/mpi/mpi-mul.c
> +++ b/lib/mpi/mpi-mul.c
> @@ -21,7 +21,6 @@ void mpi_mul(MPI w, MPI u, MPI v)
>   	int usign, vsign, sign_product;
>   	int assign_wp = 0;
>   	mpi_ptr_t tmp_limb = NULL;
> -	unsigned int tmp_limb_nlimbs = 0;
>   
>   	if (u->nlimbs < v->nlimbs) {
>   		/* Swap U and V. */
> @@ -55,7 +54,6 @@ void mpi_mul(MPI w, MPI u, MPI v)
>   	} else { /* Make U and V not overlap with W.	*/
>   		if (wp == up) {
>   			/* W and U are identical.  Allocate temporary space for U. */
> -			tmp_limb_nlimbs = usize;
>   			up = tmp_limb = mpi_alloc_limb_space(usize);
>   			/* Is V identical too?  Keep it identical with U.  */
>   			if (wp == vp)
> @@ -64,7 +62,6 @@ void mpi_mul(MPI w, MPI u, MPI v)
>   			MPN_COPY(up, wp, usize);
>   		} else if (wp == vp) {
>   			/* W and V are identical.  Allocate temporary space for V. */
> -			tmp_limb_nlimbs = vsize;
>   			vp = tmp_limb = mpi_alloc_limb_space(vsize);
>   			/* Copy to the temporary space.  */
>   			MPN_COPY(vp, wp, vsize);
> diff --git a/lib/mpi/mpih-div.c b/lib/mpi/mpih-div.c
> index 182a656a1ba0..be70ee2e42d3 100644
> --- a/lib/mpi/mpih-div.c
> +++ b/lib/mpi/mpih-div.c
> @@ -31,7 +31,7 @@ mpihelp_mod_1(mpi_ptr_t dividend_ptr, mpi_size_t dividend_size,
>   {
>   	mpi_size_t i;
>   	mpi_limb_t n1, n0, r;
> -	mpi_limb_t dummy;
> +	mpi_limb_t dummy __maybe_unused;
>   
>   	/* Botch: Should this be handled at all?  Rely on callers?	*/
>   	if (!dividend_size)
> @@ -382,7 +382,7 @@ mpihelp_divmod_1(mpi_ptr_t quot_ptr,
>   {
>   	mpi_size_t i;
>   	mpi_limb_t n1, n0, r;
> -	mpi_limb_t dummy;
> +	mpi_limb_t dummy __maybe_unused;
>   
>   	if (!dividend_size)
>   		return 0;
>