On 19/11/2024 20:02, Paul Eggert wrote:
On 2024-11-19 09:53, Pádraig Brady wrote:
Do we really want to treat NUL and NULL strings differently?
$ src/printf '%d\n'
0
$ src/printf '%d\n' ''
printf: ‘’: expected a numeric value
0
Both behaviors are required by POSIX, so yes, we want to treat them
differently. Also, it makes sense to treat '' like ' '; we report an
error for the latter so we should report it for the former too.
Well POSIX isn't explicit about the empty case.
The closest it specifies I think is:
"If an argument operand cannot be completely converted into an
internal value appropriate to the corresponding conversion specification,
a diagnostic message shall be written to standard error"
But one could consider an empty argument as completely converted?
I'm not very strongly against the change,
it just seems a little inconsistent to me to error for the empty argument
to numeric conversion case, when we don't do that for strings.
Also I'm a bit worried about quoting consequences for shell scripts.
For example scripts with `printf '%d\n' "$int"` will start erroring if int is
not defined,
whereas arguably less protected scripts with `printf '%d\n' $int` will behave
(correctly) as before.
That's different to bash and dash.
AIX and Solaris 10 printf do things the right way (i.e., conform to
POSIX) - not surprising as AIX at least has gone through POSIX
conformance tests. I expect the GNU divergence from tradition was
accidental, as it doesn't make sense for printf to treat '' differently
from other non-numbers.
I filed bug reports for both Bash and Dash; see:
https://lists.gnu.org/r/bug-bash/2024-11/msg00149.html
https://lore.kernel.org/dash/20241119193211.1585716-1-egg...@cs.ucla.edu/T/#u
For completeness ksh on Solaris 11 treats empty as 0
solaris11$ printf --version
version printf (AT&T Research) 2009-02-02
solaris11:~$ printf '%d\n' ''
0
As does newer ksh:
fedora40$ printf --version
version printf (ksh 93u+m) 2023-03-23
fedora40$ printf '%d\n' ''
0
Though I also see that ksh treats any non number as 0.
cheers,
Pádraig
