Re: [PATCH 2/3] utils: Deprecate hex-with-suffix sizes

[Daniel P . Berrangé]

On Thu, Feb 04, 2021 at 01:07:07PM -0600, Eric Blake wrote:
> Supporting '0x20M' looks odd, particularly since we have an 'E' suffix
> that is ambiguous between a hex digit and the extremely large exibyte
> suffix, as well as a 'B' suffix for bytes.  In practice, people using
> hex inputs are specifying values in bytes (and would have written
> 0x2000000, or possibly relied on default_suffix in the case of
> qemu_strtosz_MiB), and the use of scaling suffixes makes the most
> sense for inputs in decimal (where the user would write 32M).  But
> rather than outright dropping support for hex-with-suffix, let's
> follow our deprecation policy.  Sadly, since qemu_strtosz() does not
> have an Err** parameter, we pollute to stderr.

Err** is only appropriate for errors, not warnings, so this statement
can be removed.

> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  docs/system/deprecated.rst | 8 ++++++++
>  util/cutils.c              | 6 +++++-
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
> index 6ac757ed9fa7..c404c3926e6f 100644
> --- a/docs/system/deprecated.rst
> +++ b/docs/system/deprecated.rst
> @@ -146,6 +146,14 @@ library enabled as a cryptography provider.
>  Neither the ``nettle`` library, or the built-in cryptography provider are
>  supported on FIPS enabled hosts.
> 
> +hexadecimal sizes with scaling multipliers (since 6.0)
> +''''''''''''''''''''''''''''''''''''''''''''''''''''''
> +
> +Input parameters that take a size value should only use a size suffix
> +(such as 'k' or 'M') when the base is written in decimal, and not when
> +the value is hexadecimal.  That is, '0x20M' is deprecated, and should
> +be written either as '32M' or as '0x2000000'.
> +
>  QEMU Machine Protocol (QMP) commands
>  ------------------------------------
> 
> diff --git a/util/cutils.c b/util/cutils.c
> index 0234763bd70b..75190565cbb5 100644
> --- a/util/cutils.c
> +++ b/util/cutils.c
> @@ -264,7 +264,7 @@ static int do_strtosz(const char *nptr, const char **end,
>      int retval;
>      const char *endptr;
>      unsigned char c;
> -    bool mul_required = false;
> +    bool mul_required = false, hex = false;
>      uint64_t val;
>      int64_t mul;
>      double fraction = 0.0;
> @@ -309,6 +309,10 @@ static int do_strtosz(const char *nptr, const char **end,
>      c = *endptr;
>      mul = suffix_mul(c, unit);
>      if (mul > 0) {
> +        if (hex) {
> +            fprintf(stderr, "Using a multiplier suffix on hex numbers "
> +                    "is deprecated: %s\n", nptr);

warn_report(), since IIUC, that'll get into HMP response correctly.

> +        }
>          endptr++;
>      } else {
>          mul = suffix_mul(default_suffix, unit);

Regards,
Daniel
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