in reply to Re: XS: exposing C++ library constant as package variable
in thread XS: exposing C++ library constant as package variable

As for caveats with regard to threading

It's a normal Perl scalar. It will get cloned on thread creation like every other. Each thread will be accessing its own copy of it. No problem.

Update: s/a different/its own/

  • Comment on Re^2: XS: exposing C++ library constant as package variable

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Re^3: XS: exposing C++ library constant as package variable
by syphilis (Archbishop) on Oct 08, 2015 at 05:27 UTC
    Each thread will be accessing a different copy of it

    I would have expected the copies to be identical, and that the SvREADONLY_on would ensure that they stay identical.
    Of course, my expectations are often wrong - especially re threads. (IOW, someone please correct me where necessary.)

    Cheers,
    Rob
[reply]
      yes, they're identical copies 
      $ perl -le "sub LUCY(){66} use threads; async{ print join q/ /, thread
+s->tid, LUCY(), \&LUCY() } for 1..3; sleep 1; "
1 66 SCALAR(0xb6c0d4)
2 66 SCALAR(0xbf7144)
3 66 SCALAR(0xc7eebc)
Perl exited with active threads:
        0 running and unjoined
        3 finished and unjoined
        0 running and detached

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      $ perl -le "use Readonly; Readonly::Scalar $LU => 66; use threads; asy
+nc{ print join q/ /, threads->tid, $LU, \$LU } for 1..3; sleep 1; "
1 66 SCALAR(0xb84cfc)
2 66 SCALAR(0xc1bbec)
3 66 SCALAR(0x10af0b4)
Perl exited with active threads:
        0 running and unjoined
        3 finished and unjoined
        0 running and detached

      [download]
[reply]
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      Of course they're identical copies; I was saying that each thread gets its own copy. Updated wording in this post's grandparent.
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