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printf: allow 0 as a flag and allow multiple flags

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The '%' character in a format specification may be followed by
one or more flags from the list "+- #0".  BusyBox printf didn't
support the '0' flag or allow multiple flags to be provided.
As a result the formats '%0*d' and '%0 d' were considered to be
invalid.

The lack of support for '0' was pointed out by Andrew Snyder on the
musl mailing list:

   https://www.openwall.com/lists/musl/2021/12/14/2

function                                             old     new   delta
printf_main                                          860     891     +31
.rodata                                            99281   99282      +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 32/0)               Total: 32 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Ron Yorston 2021-12-16 11:19:03 +00:00 committed by Denys Vlasenko
parent b720629dfe
commit 7105e4afdd
2 changed files with 11 additions and 1 deletions
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2
coreutils/printf.c
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@ -313,7 +313,7 @@ static char **print_formatted(char *f, char **argv, int *conv_err)
} }
break; break;
} }
if (*f && strchr("-+ #", *f)) { while (*f && strchr("-+ #0", *f)) {
++f; ++f;
++direc_length; ++direc_length;
} }

10
testsuite/printf.tests
View File

@ -143,4 +143,14 @@ testing "printf aborts on %r" \
"printf: %r: invalid format\n""1\n" \ "printf: %r: invalid format\n""1\n" \
"" "" "" ""
testing "printf treats leading 0 as flag" \
"${bb}printf '%0*d\n' 2 1 2>&1; echo \$?" \
"01\n""0\n" \
"" ""
testing "printf handles multiple flags" \
"${bb}printf '%0 d\n' 2 2>&1; echo \$?" \
" 2\n""0\n" \
"" ""
exit $FAILCOUNT exit $FAILCOUNT