Hi monks

I found that perlcall and perlxs treat mortal variable are different. When you calls perl subroutine from C, you have to save and free them manually, but in XS code, you don't have to do that. like: 

#in perlcall, you have to use ENTER,SAVETMPS, FREETMPS, LEAVE to free 
+mortal variables
 dSP;

    ENTER;
    SAVETMPS;

    PUSHMARK(SP);
    EXTEND(SP, 2);
    PUSHs(sv_2mortal(newSVpv(a, 0)));
    PUSHs(sv_2mortal(newSViv(b)));
    PUTBACK;

    call_pv("LeftString", G_DISCARD);

    FREETMPS;
    LEAVE;

#in XS, you don't have to do that:
void
rpcb_gettime(host)
     char *host
   PREINIT:
     time_t  timep;
     bool_t  status;
   PPCODE:
     status = rpcb_gettime( host, &timep );
     EXTEND(SP, 2);
     PUSHs(sv_2mortal(newSViv(status)));
     PUSHs(sv_2mortal(newSViv(timep)));

[download]
I've searched C file generated by XS, there are still no any code to free mortal variables. So When these mortal variable are freed? Please enlightened me. TIA.


I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction

In reply to What does XSUB do on TMPS Stack for us? by xiaoyafeng

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