Chapter 10

Next, the Inline_Stack_Vars macro is used to initialize temporaries for the 

Inline::C stack macros:

Inline_Stack_Vars;

The next new macro usage is the pair Inline_Stack_Reset and Inline_Stack_Done.

These are required around any usage of Inline_Stack_Push. These macros push the list 

of key/value pairs onto the return stack:

    // get ready for Inline_Stack_Push

    Inline_Stack_Reset;

    // loop over key/value pairs

    for (i = 1; i <= count; i++) {

      value = hv_iternextsv(hv, &key, &len);

      // push key and value

      Inline_Stack_Push(sv_2mortal(newSVpvn(key, len)));

      Inline_Stack_Push(sv_mortalcopy(value));

    }

    // done pushing on the stack

    Inline_Stack_Done;

Then Inline::C's version of XSRETURN, Inline_Stack_Return, is used to return from the 

function:

    // return two SVs for each key in the hash

    Inline_Stack_Return(count * 2);

A similar sequence is used in scalar context to return a single value:

  // G_SCALAR or G_VOID context   return a reference to the new hash

  Inline_Stack_Reset;

  Inline_Stack_Push(sv_2mortal(newRV_noinc((SV *)hv)));

  Inline_Stack_Done;

  Inline_Stack_Return(1);

This marks a difference from the XS code where the final XSRETURN(1) wasn't 

required; in Inline::C Inline_Stack_Return is a required call regardless of the 

number of return values.

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