something weird with strerror_r

[Mike Parker via Digitalmars-d]

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() );
}