Re: [PATCH v3 19/19] cutils: Improve qemu_strtosz handling of fractions

From: Eric Blake <eblake@redhat.com>
To: qemu-devel@nongnu.org
Cc: hreitz@redhat.com, qemu-block@nongnu.org
Subject: Re: [PATCH v3 19/19] cutils: Improve qemu_strtosz handling of fractions
Date: Thu, 1 Jun 2023 16:46:57 -0500	[thread overview]
Message-ID: <pkk2whklk5ceqypnfvc7kdycic677oajez6oh7iuftcodhw4po@bousmxdkzgjv> (raw)
In-Reply-To: <20230522190441.64278-20-eblake@redhat.com>

On Mon, May 22, 2023 at 02:04:41PM -0500, Eric Blake wrote:
> We have several limitations and bugs worth fixing; they are
> inter-related enough that it is not worth splitting this patch into
> smaller pieces:
> 
> +++ b/util/cutils.c
> @@ -194,15 +194,18 @@ static int64_t suffix_mul(char suffix, int64_t unit)
>   * - 12345 - decimal, scale determined by @default_suffix and @unit
>   * - 12345{bBkKmMgGtTpPeE} - decimal, scale determined by suffix and @unit
>   * - 12345.678{kKmMgGtTpPeE} - decimal, scale determined by suffix, and
> - *   fractional portion is truncated to byte
> + *   fractional portion is truncated to byte, either side of . may be empty
>   * - 0x7fEE - hexadecimal, unit determined by @default_suffix
>   *
>   * The following are intentionally not supported
> - * - hex with scaling suffix, such as 0x20M
> - * - octal, such as 08
> - * - fractional hex, such as 0x1.8
> - * - negative values, including -0
> - * - floating point exponents, such as 1e3
> + * - hex with scaling suffix, such as 0x20M (0x1b is 27, not 1)
> + * - octal, such as 08 (parsed as decimal instead)
> + * - binary, such as 0b1000 (parsed as 0b with trailing garbage "1000")
> + * - fractional hex, such as 0x1.8 (parsed as 0 with trailing garbage "x1.8")
> + * - negative values, including -0 (fail with -ERANGE)
> + * - floating point exponents, such as 1e3 (parsed as 1e with trailing
> + *   garbage "3") or 0x1p3 (parsed as 1 with trailing garbage "p3")

This latter clause is wrong - we reject 0x1p3 earlier under the hex
with scaling suffix rule.  I've touched up the comment as part of
preparing the pull request.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org