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[PATCH v2 3/4] utils: Deprecate hex-with-suffix sizes

From: Eric Blake
Subject: [PATCH v2 3/4] utils: Deprecate hex-with-suffix sizes
Date: Thu, 11 Feb 2021 14:44:37 -0600

Supporting '0x20M' looks odd, particularly since we have a 'B' suffix
that is ambiguous for bytes, as well as a less-frequently-used 'E'
suffix for extremely large exibytes.  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, and plumbing that in would be a much larger
task, we instead go with just directly emitting the deprecation
warning to stderr.

Signed-off-by: Eric Blake <eblake@redhat.com>
 docs/system/deprecated.rst |  8 ++++++++
 util/cutils.c              | 10 +++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index 2fcac7861e07..113c2e933f1b 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 22d27b0fd21b..6a8a175e0d71 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -250,6 +250,9 @@ static int64_t suffix_mul(char suffix, int64_t unit)
  *   fractional portion is truncated to byte
  * - 0x7fEE - hexadecimal, unit determined by @default_suffix
+ * The following cause a deprecation warning, and may be removed in the future
+ * - 0xabc{kKmMgGtTpP} - hex with scaling suffix
+ *
  * The following are intentionally not supported
  * - octal, such as 08
  * - fractional hex, such as 0x1.8
@@ -272,7 +275,7 @@ static int do_strtosz(const char *nptr, const char **end,
     int retval;
     const char *endptr, *f;
     unsigned char c;
-    bool mul_required = false;
+    bool mul_required = false, hex = false;
     uint64_t val;
     int64_t mul;
     double fraction = 0.0;
@@ -298,6 +301,7 @@ static int do_strtosz(const char *nptr, const char **end,
             retval = -EINVAL;
             goto out;
+        hex = true;
     } else if (*endptr == '.') {
          * Input looks like a fraction.  Make sure even 1.k works
@@ -320,6 +324,10 @@ static int do_strtosz(const char *nptr, const char **end,
     c = *endptr;
     mul = suffix_mul(c, unit);
     if (mul > 0) {
+        if (hex) {
+            warn_report("Using a multiplier suffix on hex numbers "
+                        "is deprecated: %s", nptr);
+        }
     } else {
         mul = suffix_mul(default_suffix, unit);

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