Recently I tried my first XS code for Devel-Hook dist (http://search.cpan.org/dist/Devel-Hook).
There I tried to include conditional compilation for dealing with UNITCHECK blocks (introduced at perl 5.9.4 IIRC) by testing if PL_unitcheckav (the internal array of UNITCHECK blocks that the interpreter maintains) was defined or not: The code is at: http://search.cpan.org/src/FERREIRA/Devel-Hook-0.004/Hook.xs And the relevant part is: AV *_get_unitcheck_array() { #ifdef PL_unitcheckav if ( !PL_unitcheckav ) { PL_unitcheckav = newAV(); } return PL_unitcheckav; #else croak( "UNITCHECK not implemented in this release of perl" ); #endif } But I found that this just doesn't work in certain installations of Perl. Even with Perl 5.10.0, the above function was expanded to: AV *_get_unitcheck_array() { croak( "UNITCHECK not implemented in this release of perl" ); } What suggested me this approach was that PL_unitcheckav was defined as a #define at "perlapi.h". But when I looked closer at the result of the preprocessor, I saw that there was an actual symbol "PL_unitcheckav" as well. Maybe that's the reason it did not work out. (I am not sure as I am rusty with C programming and understand very little of Perl internals programming). A working solution that I found was including "keywords.h" and testing for "KEY_UNITCHECK" (as done here: http://search.cpan.org/src/FERREIRA/Devel-Hook-0.005/Hook.xs) #include "keywords.h" [ ... ] AV *_get_unitcheck_array() { #ifdef KEY_UNITCHECK if ( !PL_unitcheckav ) { PL_unitcheckav = newAV(); } return PL_unitcheckav; #else croak( "UNITCHECK not implemented in this release of perl" ); #endif } That works fine as intented. But it seems weird to me. So my doubt is: what is the right way to do it? Where can I find more about doing proper XS coding and programming with the Perl API? I could not see any of this in "perlxs", "perlxstut", "perlapi", "perlguts", etc. Regards, Adriano Ferreira P.S. Another perplexing behavior was that at CPAN Testers reports: http://cpantesters.perl.org/show/Devel-Hook.html#Devel-Hook-0.004 there were two PASS tests (as I would have expected since the conditional compiling was defaulting to say that UNITCHECK was not supported) but also three FAIL tests (which could only be triggered because the conditional compilation actually worked in these installations and hitted a test bug - only reachable if UNITCHECK support was detected).
