Re: xs modifying passed value

[Festus Hagen]

Results after hacking up Bulk88's righteous work into my deeper needs!

Mucho Thanks for the kick in the git go.

int 
MyLib::strToInt(...)
PREINIT:
    SV* passfailSV;
    bool passfail;
CODE:
    if(items == 2) {
        SV* passfailSV = ST(1);
        RETVAL = THIS->strToInt(&passfail);
        SvSetMagicSV(passfailSV, passfail ? &PL_sv_yes : &PL_sv_no);
    } else if(items == 1) {
        RETVAL = THIS->strToInt();
    } else
        croak("Usage: MyLib->strToInt(...)");
OUTPUT:
    RETVAL

Critiques ??
Comments ??
Suggestions ??
Improvements ??

-Enjoy
fh : )_~

[bulk88]

Considered having the return of MyLib::strToInt be the bool, and the param be the int? Usually subs/funcs return true false, and details of the operation are inplace updates/ pass by reference/ $_[0] = "hello";/*status = 1;/. Or the author of C++ method strToInt did it that way and thats the way you will remember it in Perl? You could also return 2 elements "($truefalse, $theint) = $instance->strToInt();", and have MyLib::strToInt method take only one param (THIS scalar). If the caller in perl doesn't want the int, they dont need to collect it in list context.

edit: With XS/C/Perl internals, the biggest XSUB debugging tool is looking at the .c code. Try posting that. For C code, you should learn how to create post C processor code, then run it through a code formatter. A 7 character named macro taking 1 param, barely or terribly documented, can expand to a screenful of code after 2-5 layers of macros are expanded. To understand why it failed, looking at the post preprocessor output it the only way. Also compile with optimize=debug and symbols, as you said already, you have a C debugger, so thats correct. Also instead of returning 1 bool, or a list, consider returning a hashref, a hashref is probably overkill for this function.

[bulk88]

Some people for param lists do,

my %localdog;
if(@_ == 2  && ref($_[1]) eq 'HASH') {
#named params
     my $hvref = $_[1];
     $localdog{name} = $hvref->{name};
     $localdog{color} = $hvref->{color};
}
else{
     $localdog{name} = $_[1];
     $localdog{color} = $_[2];
}