Using DEFSV

[Tassilo von Parseval]

Hi,

suppose I want to trigger external Perl subroutines but don't want to
pass the argument via the stack but rather by setting $_. Is the
following correct?

    void call_coderef (SV *coderef, char *path) {
        SV *src;
        dSP;

        SAVESPTR(DEFSV);

        ENTER;
        SAVETMPS;
        PUSHMARK(SP);
        DEFSV = sv_2mortal(newSVpvn(path, strlen(path)));
        PUTBACK;
        (void) call_sv(coderef, G_DISCARD);
        
        FREETMPS;
        LEAVE;
    }

Some non-thorough empirical tests suggest that it is neither leaking
memory nor is the old value of $_ destroyed:

    $_ = "bla";
    code_that_calls_above_coderef();
    ok($_ eq "bla");    # $_ has been restored apparently

But surely, it can't be that simple, can it?

Tassilo
-- 
$_=q#",}])!JAPH!qq(tsuJ[{@"tnirp}3..0}_$;//::niam/s~=)]3[))_$-3(rellac(=_$({
pam{rekcahbus})(rekcah{lrePbus})(lreP{rehtonabus})!JAPH!qq(rehtona{tsuJbus#;
$_=reverse,s+(?<=sub).+q#q!'"qq.\t$&."'!#+sexisexiixesixeseg;y~\n~~dddd;eval