On 12/12/23 22:05, spender wrote:
printf("%c",ch), the ch must <0xFF, <255
The only 'ch' in the code that you responded to was declared as
"char *", not char, [...]
Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
Lew Pitcher <lew.pitcher@digitalfreehold.ca> writes:
On Wed, 13 Dec 2023 11:05:45 +0800, spender wrote:
printf("%c",ch), the ch must <0xFF, <255
Not quite.
1) ch /must/ represent an integer value.
More specifically, it must have a type that is or promotes
to int, or a type that is or promotes to unsigned int, with
a value that is in the common range of int and unsigned int.
Not quite. "If no l length modifier is present, the int argument
is converted to an unsigned char, and the resulting character is
written." For example printf("%c", -193) is equivalent to
printf("%c", 63), which assuming an ASCII-based character set will
print '?'.
Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
Lew Pitcher <lew.pitcher@digitalfreehold.ca> writes:
On Wed, 13 Dec 2023 11:05:45 +0800, spender wrote:
printf("%c",ch), the ch must <0xFF, <255
Not quite.
1) ch /must/ represent an integer value.
More specifically, it must have a type that is or promotes
to int, or a type that is or promotes to unsigned int, with
a value that is in the common range of int and unsigned int.
Not quite. "If no l length modifier is present, the int argument
is converted to an unsigned char, and the resulting character is
written." For example printf("%c", -193) is equivalent to
printf("%c", 63), which assuming an ASCII-based character set will
print '?'.
The rule for arguments to printf() is the same as the rule for
accessing variadic arguments using va_arg(). That has always
been true, although not expressed clearly in early versions of
the C standard. Fortunately that shortcoming is addressed in
the upcoming C23 (is it still not yet ratified?): in N3096,
paragraph 9 in section 7.23.6.1 says in part
fprintf shall behave as if it uses va_arg with a type
argument naming the type resulting from applying the
default argument promotions to the type corresponding
to the conversion specification [...]
and the rule for va_arg (in 7.16.1.1 p2) says in part
one type is a signed integer type, the other type is
the corresponding unsigned integer type, and the value
is representable in both types
So supplying an unsigned int argument is okay, provided of
course the value is in the range of values of signed int.
Re-reading what you wrote, I think I misunderstood your intent (and I
think what you wrote was ambiguous).
"%c" specifies an int argument.
You wrote:
More specifically, it must have a type that is or promotes to int,
or a type that is or promotes to unsigned int, with a value that is
in the common range of int and unsigned int.
I read that as:
More specifically,
(it must have a type that is or promotes to int, or a type that is
or promotes to unsigned int),
with a value that is in the common range of int and unsigned int.
which would incorrectly imply that a negative int value is not allowed.
It's now clear to me that you meant was:
More specifically,
(it must have a type that is or promotes to int),
or
(a type that is or promotes to unsigned int, with a value that is in
the common range of int and unsigned int).
I agree with that.
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