"sv_bless( self, gv_stashpv( class, 0 ) )" issue

[bulk88]

    /* bless into the proper package */
    RETVAL = sv_bless( self, gv_stashpv( class, 0 ) );
    OUTPUT: RETVAL

https://github.com/xsawyerx/xs-fun/blame/master/chapter_03/chapter_03.pod#L170

you should use gv_stashsv instead of gv_stashpv since your input is already a SV, rurban mentioned on #p5p that strlen on the package name could produce an obj blessed into a different package than the one passed in if the package name contains nulls

[xsawyerx]

Good point! Will change that soon.

[xsawyerx]

When I change it to gv_stashsv, all the tests fail and it can't load it.

Also, I don't understand the comment on strlen.

[bulk88]

To be precise, to use gv_stashsv

SV *
new( const char *class )

needs to be changed to

SV *
new( SV  *class )

also the 2 mentions of gv_stashpv in the docs need to be then changed to gv_stashsv. You will loose some educational content since after converting to gv_stashsv, there will be zero uses of a "char *" as an incoming param to a xsub in xs-fun (but there still will be a couple uses of char * as an scalar return value in chap 0-2, but those dont really explain how incoming args work).

gv_stashpv("foo\x00\x00",0) and gv_stashpvn("foo\x00\x00", sizeof("foo\x00\x00"), 0) will produce objs from 2 different classes, strlen("foo\x00\x00") is 3, not 5. As an example why null would wind up in a package name, some crazy people quote file paths in Perl with $path = q[NUL]/bin/foo[NUL]; in source code, since null char is the only character that can not be in a file path in POSIX. Until 5.9.3 http://perl5.git.perl.org/perl.git/commitdiff/7423f6db106ad471398838e82e73b22d8c1e166e , package names could not have null in them since they were null terminated.

[xsawyerx]

That is pretty cool. Thank you so much for the explanation of strings and nulls in packages.

I can't find a way to incorporate that into the tutorial (feel free to offer, if you have any idea), but I'll change the stashpv to stashsv because it's just correct.

[bulk88]

In, https://github.com/xsawyerx/xs-fun/blob/master/chapter_03/chapter_03.pod it says

    # Perl on GNU/Linux, BSD, Solaris:
    perl Makefile.PL && make manifest && make distclean

    # Strawberry Perl on Windows:
    perl Makefile.PL
    dmake manifest
    dmake distclean

Windows has "&" and "&&", IDK if their meaning is exactly identical to unix, see http://ss64.com/nt/syntax-conditional.html . If you want for style reasons to make the windows version look more the unix version by putting it all on 1 line, you can.

In https://github.com/xsawyerx/xs-fun/blob/master/chapter_02/chapter_02.pod , IDK if you are writing for a Perl crowd (pointer is a shaky red dot on the projector screen), or a C but no XS/perlapi crowd, but I have to ask the question, what frees the char * returned by chromaprint_get_version()? does it need to be freed? you might want to touch on that topic (even though it is basic C knowledge), don't write to SvPV returned string ptrs. And perl will never free your string * automatically (except for sv_usepvn_flags, and the save stack, but they really dont need to know about those 2 unless you plan to rename this repo to XS-Doctorate)

[paultcochrane]

Just to make a note of it: the Windows "&&" issue mentioned above was fixed in 517b051a7ad76e97034cb5e9748ab11dc254a47a.