gimple-ssa-sprintf: Use [0, 1] range for %lc with (wint_t) 0 argument [PR114876]

gimple-ssa-sprintf: Use [0, 1] range for %lc with (wint_t) 0 argument [PR114876]

Seems when Martin S. implemented this, he coded there strict reading
of the standard, which said that %lc with (wint_t) 0 argument is handled
as wchar_t[2] temp = { arg, 0 }; %ls with temp arg and so shouldn't print
any values.  But, most of the libc implementations actually handled that
case like %c with '\0' argument, adding a single NUL character, the only
known exception is musl.
Recently, C23 changed this in response to GB-141 and POSIX in
https://austingroupbugs.net/view.php?id=1647
so that it should have the same behavior as %c with '\0'.

Because there is implementation divergence, the following patch uses
a range rather than hardcoding it to all 1s (i.e. the %c behavior),
though the likely case is still 1 (forward looking plus most of
implementations).
The res.knownrange = true; assignment removed is redundant due to
the same assignment done unconditionally before the if statement,
rest is formatting fixes.

I don't think the min >= 0 && min < 128 case is right either, I'd think
it should be min >= 0 && max < 128, otherwise it is just some possible
inputs are (maybe) ASCII and there can be others, but this code is a total
mess anyway, with the min, max, likely (somewhere in [min, max]?) and then
unlikely possibly larger than max, dunno, perhaps for at least some chars
in the ASCII range the likely case could be for the ascii case; so perhaps
just the one_2_one_ascii shouldn't set max to 1 and mayfail should be true
for max >= 128.  Anyway, didn't feel I should touch that right now.

2024-04-30  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/114876
	* gimple-ssa-sprintf.cc (format_character): For min == 0 && max == 0,
	set max, likely and unlikely members to 1 rather than 0.  Remove
	useless res.knownrange = true;.  Formatting fixes.

	* gcc.dg/pr114876.c: New test.
	* gcc.dg/tree-ssa/builtin-sprintf-warn-1.c: Adjust expected
	diagnostics.