Re^2: Win32, fork and XS globals

[ikegami]

in reply to Re: Win32, fork and XS globals
in thread Win32, fork and XS globals

That perlmod link is not terribly useful. For instructions on creating per-interpreter variables, see "Safely Storing Static Data in XS" in perlxs. It even includes an example.

The mechanism allows each interpreter in a process to have their own copies of variables. This is useful not only when threads are involved, but in all instances when a process has multiple Perl interpreters (e.g. mod_perl?).

[BrowserUk]

It even includes an example.

Personally, I found that example almost completely useless. An example of "Safely Storing Static Data" that doesn't appear to declare any static data is pretty worthless.

And having half a dozen macros all named SOM_BG_MNGLSS_ABBREV only differentiated by a single even more meaningless, wimpy prefix character a or d or p or maybe an almost invisible _ prefix or suffix, is stupid, bordering on the criminal.

Which is why I didn't mention it.

Of course, if you'd offered this information as a reply to the OP rather throwing it at me, you wouldn't have got this response.

[ikegami]

Of course it's not allocated statically. It can't be both static and per-interpreter.

"_" represents the even less visible ",", so complaints of visibility are silly.

"d", "a" and "p" stand for "declare", "argument" and "parameter", and are used throughout the API just like "SV". The pattern is documented. There's a point as uses grows where short and convenient becomes more convenient than crystal clarity, and the use of "d", "a" and "p" are justified or nearly justified by this (like $_ is).

[BrowserUk]

Why not address your replies to the person asking the question, cos I already know this stuff.

[syphilis]

Be buggered ... this actually seems to work:

use warnings;

use Inline C => Config =>
     NAME => 'expt',
     BOOT => 
"
  {
  MY_CXT_INIT;
  MY_CXT.count = 5;
  }
",
    BUILD_NOISY => 1,
;

use Inline C => <<'EOC';

#define MY_CXT_KEY "expt::_guts" XS_VERSION

typedef struct {
  int count;
} my_cxt_t;

START_MY_CXT


void set_x(int z) {
   dMY_CXT;
   MY_CXT.count = z;
}

void get_x(char * id) {
   dMY_CXT;
   printf("%s %d\n", id, MY_CXT.count);
}

void CLONE(SV * x, ...) {
   MY_CXT_CLONE;
}

EOC

get_x('1st call:');

if($pid = fork()) {
  waitpid($pid,0);
} else {
  set_x(10);
  get_x('2nd call:');
  exit(0);
}
 
get_x('3rd call:');

It outputs:

1st call: 5
2nd call: 10
3rd call: 5

Must investigate further.

Cheers,
Rob