From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: [PATCH] fix printf regression with alt-form octal, default precision
Date: Thu, 15 Sep 2016 12:37:57 -0400 [thread overview]
Message-ID: <20160915163757.GK15995@brightrain.aerifal.cx> (raw)
In-Reply-To: <20160804010740.GA12707@altlinux.org>
[-- Attachment #1: Type: text/plain, Size: 1315 bytes --]
On Thu, Aug 04, 2016 at 04:07:40AM +0300, Dmitry V. Levin wrote:
> commit v1.1.5-10-gb91cdbe2bc8b626aa04dc6e3e84345accf34e4b1 that fixed
> behavior of printf with alt-form octal, zero precision, zero value,
> at the same time broke alt-form octal with default precision,
> e. g. printf("%#09o", 1).
> ---
> src/stdio/vfprintf.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c
> index 2ecf769..ac2891c 100644
> --- a/src/stdio/vfprintf.c
> +++ b/src/stdio/vfprintf.c
> @@ -570,7 +570,14 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
> if (0) {
> case 'o':
> a = fmt_o(arg.i, z);
> - if ((fl&ALT_FORM) && p<z-a+1) p=z-a+1;
> + if (fl&ALT_FORM) {
> + if (p >= 0 && p<z-a+1) {
> + p=z-a+1;
> + } else if (arg.i) {
> + prefix+=5;
> + pl=1;
> + }
> + }
> } if (0) {
> case 'd': case 'i':
> pl=1;
I think the attached simpler patch should work just as well. Adjusting
'p' to implement '#' was probably a bad idea since it makes the later
code paths think an explicit precision was specified when it was not.
"Add a prefix of '0' when p is too short to have a leading '0'
already" seems like safer logic.
I'm also attaching some test cases I ran.
Rich
[-- Attachment #2: octal_alt_form.diff --]
[-- Type: text/plain, Size: 435 bytes --]
diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c
index 2ecf769..e439a07 100644
--- a/src/stdio/vfprintf.c
+++ b/src/stdio/vfprintf.c
@@ -570,7 +570,7 @@ static int printf_core(FILE *f, const char *fmt, va_list *ap, union arg *nl_arg,
if (0) {
case 'o':
a = fmt_o(arg.i, z);
- if ((fl&ALT_FORM) && p<z-a+1) p=z-a+1;
+ if ((fl&ALT_FORM) && p<z-a+1) prefix+=5, pl=1;
} if (0) {
case 'd': case 'i':
pl=1;
[-- Attachment #3: alt_form_octal.c --]
[-- Type: text/plain, Size: 403 bytes --]
#include <stdio.h>
int main()
{
printf("%#.0o\n", 0);
printf("%#.0o\n", 1);
printf("%#o\n", 0);
printf("%#o\n", 1);
printf("%#09o\n", 0);
printf("%#09o\n", 1);
printf("%#09.0o\n", 0);
printf("%#09.0o\n", 1);
printf("%#9o\n", 0);
printf("%#9o\n", 1);
printf("%#9.0o\n", 0);
printf("%#9.0o\n", 1);
printf("%#.1o\n", 0);
printf("%#.1o\n", 1);
printf("%#.2o\n", 0);
printf("%#.2o\n", 1);
}
next prev parent reply other threads:[~2016-09-15 16:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-04 1:07 Dmitry V. Levin
2016-09-15 16:04 ` Dmitry V. Levin
2016-09-15 16:22 ` Rich Felker
2016-09-15 16:25 ` Rich Felker
2016-09-15 16:37 ` Rich Felker [this message]
2016-09-15 18:14 ` Dmitry V. Levin
2016-09-16 21:58 ` Rich Felker
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