Re: [PATCH v2 next 10/11] selftests/nolibc: Increase coverage of printf format tests

[David Laight]

On Mon, 16 Feb 2026 21:23:50 +0100
Thomas Weißschuh <linux@xxxxxxxxxxxxxx> wrote:

> On 2026-02-06 19:11:20+0000, david.laight.linux@xxxxxxxxx wrote:
> > From: David Laight <david.laight.linux@xxxxxxxxx>
> > 
> > Extra tests include:
> > - %%, including ignored modifiers.
> > - Invalid formats copied to output buffer (matches glibc).
> > - Left aligned output "%-..."
> > - Zero padding "%0...".
> > - "(nil)" for NULL pointers (matches glibc).
> > - Alternate form "%#x" (prepends 0x in non-zero).
> > - Field precision as well as width, printf("%.0d", 0) is "".
> > - Variable length width and precision "%*.*d".
> > - Length qualifiers L and ll.
> > - Conversion specifiers i and X.
> > - More 'corner' cases.
> > 
> > There are no explicit tests of long (l, t or z) because they would
> > have to differ between 32bit and 64bit.
> > 
> > Set the expected length to zero for all the non-truncating tests.
> > (Annoying when a test is changed.)
> > 
> > Signed-off-by: David Laight <david.laight.linux@xxxxxxxxx>
> > ---
> > 
> > Changes for v2:
> > - Formally patch 11.
> > - Remove broken __attribute__ on expect_vfprintf().
> > - Add extra test for "#01x".
> > 
> >  tools/testing/selftests/nolibc/nolibc-test.c | 49 +++++++++++++++-----
> >  1 file changed, 37 insertions(+), 12 deletions(-)  
> 
> (...)
> 
> > +		CASE_TEST(num_pad_trunc);EXPECT_VFPRINTF(40, "          0000000000", "%040d", 5); break;  /* max 30 '0' can be added */  
> 
> This fails in 'libc-test' with glibc and musl:
> 
> 32 num_pad_trunc "00000000000000000000" should be "          0000000000" [FAIL]

I've a plan for that - the test needs skipping.
I can use a -40 to avoid another parameter.

	David

> 
> > +		CASE_TEST(number_prec);  EXPECT_VFPRINTF(0, "     00005", "%10.5d", 5); break;  
> 
> (...)