[PATCH] fix printf regression with alt-form octal, default precision

[PATCH] fix printf regression with alt-form octal, default precision

[Dmitry V. Levin]

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;

-- 
ldv

Re: [PATCH] fix printf regression with alt-form octal, default precision

[Dmitry V. Levin]

Ping?

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;
> 
> -- 
> ldv

-- 
ldv

Re: [PATCH] fix printf regression with alt-form octal, default precision

[Rich Felker]

On Thu, Sep 15, 2016 at 07:04:34PM +0300, Dmitry V. Levin wrote:
> Ping?
> 
> 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;
> > +				}
> > +			}

This still does not fix all cases, e.g. printf("%#09.0o\n", 0);

I'm going to try to understand what's going on and make a complete
fix.

Rich

Re: [PATCH] fix printf regression with alt-form octal, default precision

[Rich Felker]

On Thu, Sep 15, 2016 at 12:22:57PM -0400, Rich Felker wrote:
> On Thu, Sep 15, 2016 at 07:04:34PM +0300, Dmitry V. Levin wrote:
> > Ping?
> > 
> > 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;
> > > +				}
> > > +			}
> 
> This still does not fix all cases, e.g. printf("%#09.0o\n", 0);

Oh, never mind, '0' flag is specified to be ignored if a precision is
specified; this isn't a bug. I'll check and see if anything else is
wrong.

Rich

Re: [PATCH] fix printf regression with alt-form octal, default precision

[Rich Felker]

[-- 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);
}

Re: [PATCH] fix printf regression with alt-form octal, default precision

[Dmitry V. Levin]

On Thu, Sep 15, 2016 at 12:37:57PM -0400, Rich Felker wrote:
> 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
> 
> 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;

Yes, this also works, thanks.


-- 
ldv

Re: [PATCH] fix printf regression with alt-form octal, default precision

[Rich Felker]

On Thu, Sep 15, 2016 at 09:14:56PM +0300, Dmitry V. Levin wrote:
> On Thu, Sep 15, 2016 at 12:37:57PM -0400, Rich Felker wrote:
> > 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
> > 
> > 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;
> 
> Yes, this also works, thanks.

OK, I'm committing this version. Thanks!

Rich