On Thursday, 29 January 2015 at 15:25:09 UTC, Mike Parker wrote:
On 1/29/2015 11:40 PM, CodeSun wrote:
Recently, I found something really weird when I use strerror_t
function
which is declared inside std.c.string.
The code snippet is listed below:
import std.c.string;
import core.stdc.errno;
void main() {
import std.stdio;
char[128] buf;
strerror_r(errno, buf.ptr, buf.sizeof);
writeln(cast(string)buf);
}
The terminal should print "Success" with errno=0, but in this
example,
the result is
"��������������������������������������������������������������������������������������������������������������������������������".
I test this snippet both on Archlinux and Ubuntu 14.04.1, and
the result
is same. If there is someone can help me?
I wanna know if it is my mistake or it is just a bug.
Thx!
The GNU version of strerror_r is documented as returning
"a pointer to a string containing the error message. This may
be either a pointer to a string that the function stores in
buf, or a pointer to some (immutable) static string (in which
case buf is unused)."
So I think what you may have been seeing in this case is that
it was returning a static string, your buffer remained empty
and the writeln was printing a bunch of 0xFFs. Probably this is
a better way to handle it:
void main()
{
import core.stdc.errno : errno;
import std.c.string : strerror_r;
// Static arrays are initialized to T.init. For
// char, T.init is 0xFF, *not* 0. The initializer
// here will fill the array with 0.
char[ 128 ] buf = 0;
auto cstr = strerror_r( errno, buf.ptr, buf.sizeof );
// Slice the C string with fromStringz. Unlike to!string,
this
// does not allocate or copy.
import std.string : fromStringz;
writeln( cstr.fromStringz() );
}
Yes, you are right, when I printed the cstr, I got the result I
wanted. In fact, I neglect the detail you attached here from the
manual.
Thx!
