How do you want to call the C function out of Perl? I think you are looking for something like:

SV *
err_msg( code )
    int code;
  INIT:
    char sError[255];
  CODE:
    QAErrorMessage( code, sError, 255 );
    SV *result = newSVpv(sError, 0);
  OUTPUT:
    result
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void
QAErrorMessage(err_code, ret_error, bufflen)
        int     err_code
        SV*     ret_error
        int     bufflen
    OUTPUT:
        ret_error

void
QAErrorMessage(error_code)
    CASE:
        int     err_code
    PREINIT:
        int     bufflen = 256;
        char    ret_error[bufflen];
    PPCODE:
    {
         QAErrorMessage(err_code, ret_error, bufflen);
         XPUSHs(sv_2mortal( newSVpvn(ret_error,bufflen) ));
    }
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Actually when you use void in the XS sub declaration it does not prevent you using OUTPUT (although this is now deprecated) SV* is now preferred to void..... There are even examples of doing it that way in perlxstut.

Older versions of this document recommended to use void return value i
+n such cases. It was discovered that this could lead to segfaults in 
+cases when XSUB was truly void. This practice is now deprecated, and 
+may be not supported at some future version. Use the return value SV 
+* in such cases. (Currently xsubpp contains some heuristic code which
+ tries to disambiguate between ``truly-void'' and ``old-practice-decl
+ared-as-void'' functions. Hence your code is at mercy of this heurist
+ics unless you use SV * as return value.)
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cheers

tachyon

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