Re: [Libclc-developers] string function clc_stralloc()

[Hallvard B F. <h.b...@us...>]

[Bj=F8rn, you forgot cc: libclc-developers]

Bj=F8rn Augestad writes:
>Hallvard B Furuseth wrote:
>> Here is a function I've seen with several names: stralloc(), concat(=
),
>> pstrcat().  I prefer clc_str<someting>.
>> (...)
>=20
> We need an example here. The required NULL sentinel can easily be=20
> forgotten, which creates funny bugs. A simple example will do IMO.

I modified your example a bit:

EXAMPLE
    char *s =3D clc_stralloc("foo", "bar", (char *)0);
    if(s !=3D NULL) {
        puts(s);
        free(s);
    }

I prefer (char *)0 over NULL.  It's good to teach users to be careful
about the types given to variadic functions.  In this case NULL works
too, since (char*)0 has the same representation, but then users may
think this applies to other pointer types as well.

> (...)
> #include <string.h> /* for strlen() */
> (...)
> <paranoid>
> =09len may wrap around if the sum of all strlen's > SIZE_MAX.
> </paranoid>

With that test it needs to set errno, since there are two different
error conditions (too long string and malloc failed).  I've called them=

CLC_ETOOBIG and CLC_ENOMEM.  Though I'm not sure I like the CLC_ETOOBIG=

name.  Should we just use ERANGE instead of CLC_ETOOBIG?

#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <errno.h>
#include "clc_errno.h"
#include "clc_string.h"

char *
clc_stralloc(const char *arg1, ...)
{
    size_t len;
    const char *arg;
    char *ret, *end;
    va_list ap;

    len =3D 1;
    va_start(ap, arg1);
    for (arg =3D arg1; arg !=3D NULL; arg =3D va_arg(ap, const char *))=
 {
=09size_t arglen =3D strlen(arg);
=09len +=3D arglen;
=09if (len < arglen) {
=09    /* string length too large for size_t */
=09    errno =3D CLC_ETOOBIG;
=09    return NULL;
=09}
    }
    va_end(ap);

    ret =3D malloc(len);
    if (ret =3D=3D NULL) {
=09errno =3D CLC_ENOMEM;
    } else {
=09end =3D ret;
=09*end =3D '\0';
=09va_start(ap, arg1);
=09for (arg =3D arg1; arg !=3D NULL; arg =3D va_arg(ap, const char *))
=09    end =3D clc_stpcpy(end, arg);
=09va_end(ap);
    }
    return ret;
}

--=20
Hallvard