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Re: using the interfaces in ctype.h
On Apr 16, 10:24pm, woods%planix.ca@localhost ("Greg A. Woods; Planix, Inc.")
-- Subject: Re: using the interfaces in ctype.h
| On 16-Apr-08, at 6:30 PM, Christos Zoulas wrote:
| > - cast ctype arguments to unsigned char and not int, otherwise you
| > silence
| > the warning but you can still get a core-dump.
| If you're talking about the is*() and to*() APIs from libc then that
| doesn't seem to make any sense for a standards compatible program.
| The definitions in all of the standards, an in the NetBSD manual
| pages, all request that the parameters for these functions are to be
| passed as (int).
| Unfortunately even various NetBSD architectures, at least for some
| releases, are inconsistent in how these interfaces are defined and
| what warnings are given for various usages. I've had the best luck
| getting the least warnings on a wide variety of platforms by always
| casting to (int) too.
It is not an issue of avoiding the warnings. For example isspace() is
The c argument is an int, the value of which the application
shall ensure is a character representable as an unsigned char
or equal to the value of the macro EOF. If the argument has
any other value, the behavior is undefined.
So by casting a signed char to an int, you can get a large negative number
and you end up with "undefined behavior" which might mean a core dump,
so don't do it!
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