NAME
XS::Framework::Manual::SVAPI::threads - XS::Framework THREADED Perl support
THREADED Perl support
Perl has 2 options for XS when working on threaded perls:
1) Not defining PERL_NO_GET_CONTEXT. Advantage is that there is no need to put pTHX to every function signature and no need to pass it to every function which works with perl variables. Disadvatage is decreased performance on threaded perls, i.e. you trade off the convenience for performance.
2) Defining PERL_NO_GET_CONTEXT.
Unfortunatelly, as XS::Framework concept is all about sharing C code, modules that use XS::Framework cannot have different PERL_NO_GET_CONTEXT state. Because in that case, binary incompability between function signatures would occur.
XS::Framework strictly sets PERL_NO_GET_CONTEXT option, so that you have generally to accept pTHX and pass aTHX to all functions that work with perl variables. In this case you'll achieve maximum performance on threaded perls.
However, no need to write pTHX/<aTHX> every time, it is possible to have:
dTHX;at the top of those functions and actually saying revert to behaviour without PERL_NO_GET_CONTEXT (but you still need to pass aTHX to functions which are defined with pTHX, unless called via macros - like perl's API).
For example, you can't receive pTHX in C++ objects destructors, so the it is possible either write dTHX; on the top of destructor or save Perl interpreter object in constructor of your object to property named 'my_perl', or use using xs::my_perl global interpreter.
xs::my_perl
This variable holds correct perl interpreter for each thread. Via
using xs::my_perl;
auto perl_clone = perl_clone(*my_perl, 0);the my_perl is porxy object, which holds pointer to perl interperpreter.
Keep in mind that this my_perl variable is get from thread-local storage, like dTHX, so this is actually a convenience tool, reverting to performance as PERL_NO_GET_CONTEXT has not been defined. To maximize performance on threaded perls, the pTHX/aTHX should be used everywhere. It is possible to have mixed style, i.e. having using xs::my_perl and passing pTHX only for performance-critical sections.
This variable should not be used on non-threaded perls (this is not a problem as aTHX is empty in that case). However it still exists on non-threaded perls, so it is safe to have using xs::my_perl without wrapping it into #ifdef PERL_IMPLICIT_CONTEXT.