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From: Andreas Schwab <schwab@suse.de>
To: Florian Weimer <fweimer@redhat.com>
Cc: Siddhesh Poyarekar <siddhesh@gotplt.org>,  GNU C Library <libc-alpha@sourceware.org>,  Adhemerval Zanella <adhemerval.zanella@linaro.org>
Subject: Re: [PATCH] support: Add TEST_COMPARE macro
References: <8d63a2dc-f9e9-acaa-5ac5-ac5c4fbd6c9f@redhat.com>
	<8c399cde-3093-0195-a89a-ca230540cffb@gotplt.org>
	<8339a519-935a-019c-4a8f-798e37f6f346@redhat.com>
X-Yow: This is a NO-FRILLS flight -- hold th' CANADIAN BACON!!
Date: Thu, 23 Nov 2017 11:09:00 -0000
In-Reply-To: <8339a519-935a-019c-4a8f-798e37f6f346@redhat.com> (Florian
	Weimer's message of "Thu, 23 Nov 2017 11:54:05 +0100")
Message-ID: <mvmpo89z1xd.fsf@suse.de>
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On Nov 23 2017, Florian Weimer <fweimer@redhat.com> wrote:

> +/* Compare the two integers LEFT and RIGHT and report failure if they
> +   are different.  */
> +#define TEST_COMPARE(left, right)                                       \
> +  ({                                                                    \
> +    __typeof__ (left) __left_value = (left);                            \
> +    __typeof__ (right) __right_value = (right);                         \
> +    /* Prevent accidental use with larger-than-long long types.  */     \
> +    _Static_assert (sizeof (__left_value) <= sizeof (long long),        \
> +                    "left value fits into long long");                  \
> +    _Static_assert (sizeof (__right_value) <= sizeof (long long),       \
> +                    "right value fits into long long");                 \
> +    /* Compare the value and the sign, to avoid false equality.  */     \
> +    /* (A signed value could be converted to an unsigned type.)  */     \

Why do you need that?  Any signed value converted to unsigned is still
unique.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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