sort: -h now handles comparisons such as 6000K vs 5M and 5MiB vs 5MB

* NEWS: Document changes to sort -h.
* doc/coreutils.texi (sort invocation): Likewise.
* src/sort.c (long_double, strtold): Move to prelude, since they're
now used by multiple functions.
(LD): New macro.
(struct keyfield.iec_present): Remove this member.  All uses removed.
(check_mixed_SI_IEC): Remove.  This code was busted in the presence
of multiple threads, as it had a race condition.
(find_unit_order): Remove arg KEY; add arg THOU_SEP; arg ENDPTR is
now char ** rather than char const **.  Return an integer that
distinguishes decimal from binary powers.  Parse the number
consistently with the intersection of strtold and strnumcmp.
Set *ENDPTR unconditionally.
(compute_human): New static function.
(human_numcompare): Remove arg KEY.  Remove 'const' from other args.
Use strnumcmp if possible, but fall back on floating point if not.
(numcompare, general_numcompare): Arg EA is now char ** rather
than char const **.
(numcompare): Adjust to new find_unit_order signature and behavior.
(keycompare): Adjus to new human_numcompare signature.
* tests/misc/sort (h1, h3, h4, h6): Adjust to new behavior.
* tests/misc/sort-debug-keys: Likewise.

1 files changed, 13 insertions, 6 deletions

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 942978f33..4a4143039 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -3802,12 +3802,19 @@ converting to floating point.
 @opindex --sort
 @cindex human numeric sort
 @vindex LC_NUMERIC
-Sort numerically, as per the @option{--numeric-sort} option below, and in
-addition handle IEC or SI suffixes like MiB, MB etc (@ref{Block size}).
-Note a mixture of IEC and SI suffixes is not supported and will
-be flagged as an error.  Also the numbers must be abbreviated uniformly.
-I.E. values with different precisions like 6000K and 5M will be sorted
-incorrectly.
+Sort numerically, and in addition handle IEC or SI suffixes like MiB,
+MB etc (@ref{Block size}).  Each number consists of optional blanks,
+an optional @samp{-} sign, zero or more digits, optionally followed by
+a decimal-point character and zero or more digits, and optionally
+followed by an IEC or SI suffix.  A number with no digits is treated
+as @samp{0}. The @env{LC_NUMERIC} locale specifies the decimal-point
+character.
+
+Numbers containing differing suffixes are compared using
+floating-point arithmetic, and therefore may not be compared exactly
+due to rounding error.  However, the output of @command{df},
+@command{du}, and @command{ls} contains so few digits before suffixes
+that rounding error is not significant and comparisons are exact.
 
 @item -i
 @itemx --ignore-nonprinting