* [PATCH] fix float formatting of some exact halfway cases
@ 2016-10-11 22:49 Szabolcs Nagy
2016-10-20 5:55 ` Rich Felker
0 siblings, 1 reply; 2+ messages in thread
From: Szabolcs Nagy @ 2016-10-11 22:49 UTC (permalink / raw)
To: musl
in nearest rounding mode exact halfway cases were not following the
round to even rule if the rounding happened at a base 1000000000 digit
boundary of the internal representation and the previous digit was odd.
e.g. printf("%.0f", 1.5) printed 1 instead of 2.
---
src/stdio/vfprintf.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c
index e439a07..ff65295 100644
--- a/src/stdio/vfprintf.c
+++ b/src/stdio/vfprintf.c
@@ -343,7 +343,8 @@ static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
if (x || d+1!=z) {
long double round = 2/LDBL_EPSILON;
long double small;
- if (*d/i & 1) round += 2;
+ if ((*d/i & 1) || (i==1000000000 && d>a && (d[-1]&1)))
+ round += 2;
if (x<i/2) small=0x0.8p0;
else if (x==i/2 && d+1==z) small=0x1.0p0;
else small=0x1.8p0;
--
2.10.0
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] fix float formatting of some exact halfway cases
2016-10-11 22:49 [PATCH] fix float formatting of some exact halfway cases Szabolcs Nagy
@ 2016-10-20 5:55 ` Rich Felker
0 siblings, 0 replies; 2+ messages in thread
From: Rich Felker @ 2016-10-20 5:55 UTC (permalink / raw)
To: musl
On Wed, Oct 12, 2016 at 12:49:59AM +0200, Szabolcs Nagy wrote:
> in nearest rounding mode exact halfway cases were not following the
> round to even rule if the rounding happened at a base 1000000000 digit
> boundary of the internal representation and the previous digit was odd.
>
> e.g. printf("%.0f", 1.5) printed 1 instead of 2.
> ---
> src/stdio/vfprintf.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c
> index e439a07..ff65295 100644
> --- a/src/stdio/vfprintf.c
> +++ b/src/stdio/vfprintf.c
> @@ -343,7 +343,8 @@ static int fmt_fp(FILE *f, long double y, int w, int p, int fl, int t)
> if (x || d+1!=z) {
> long double round = 2/LDBL_EPSILON;
> long double small;
> - if (*d/i & 1) round += 2;
> + if ((*d/i & 1) || (i==1000000000 && d>a && (d[-1]&1)))
> + round += 2;
> if (x<i/2) small=0x0.8p0;
> else if (x==i/2 && d+1==z) small=0x1.0p0;
> else small=0x1.8p0;
> --
> 2.10.0
Thanks, committed.
Rich
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2016-10-11 22:49 [PATCH] fix float formatting of some exact halfway cases Szabolcs Nagy
2016-10-20 5:55 ` Rich Felker
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