in reply to Text::ExtractWords exhibits incomprehensible behavior?

  ibm1620 wrote: I even tried making a copy of $text (my $copy = $text) and passing $copy to words_list(), and afterwards *both* $copy and $text were munged.

That I don't understand. Were $text and $copy munged in the same way after the call or different? What does printf("%s %s\n", \$text, \$copy) give before and after the call?

In general, it seems like a bad practice for an XS function to modify it's arguments unless that is the specific purpose.

  • Comment on Re: Text::ExtractWords exhibits incomprehensible behavior?

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Re^2: Text::ExtractWords exhibits incomprehensible behavior?
by ibm1620 (Hermit) on Jun 16, 2024 at 21:39 UTC
    Yes, exact same way, despite being at different addresses: 
    #!/usr/bin/env perl
use v5.38;
use Text::ExtractWords qw(words_list);
say $^V;
my $text = "12/21/84 Bob's 21st b'day was a wine-and-dine.";
my $copy = $text;
say "Text: $text";
say "Copy: $copy";
printf("%s %s\n", \$text, \$copy);
my @list;
words_list(\@list, $copy, {minwordlen => 2, maxwordlen => 26 });
say "Found words: " . join ' ', map {"[$_]"} @list;
say "Text: $text";
say "Copy: $copy";
printf("%s %s\n", \$text, \$copy);
__END__
v5.40.0
Text: 12/21/84 Bob's 21st b'day was a wine-and-dine.
Copy: 12/21/84 Bob's 21st b'day was a wine-and-dine.
SCALAR(0x140829a68) SCALAR(0x1408299d8)
Found words: [12] [21] [84] [bob's] [21st] [b'day] [was] [a] [wine-and
+-dine]
Text: 122184bob's21stb'daywasawine-and-dine
Copy: 122184bob's21stb'daywasawine-and-dine
SCALAR(0x140829a68) SCALAR(0x1408299d8)

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      That's the SV addresses that are different. Try Devel::Peek's Dump function to see what the PV is? I suspect this is supposed to be copy-on-write (COW), but that the XS code is just overwriting the (still-shared) data area without doing the correct COW API stuff.
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        That must be it. 
        v5.40.0
Text: 12/21/84 Bob's 21st b'day was a wine-and-dine.
Copy: 12/21/84 Bob's 21st b'day was a wine-and-dine.
SV = PV(0x15780b090) at 0x1578242d0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x6000019a1fe0 "12/21/84 Bob's 21st b'day was a wine-and-dine."
+\0
  CUR = 46
  LEN = 48
  COW_REFCNT = 2
SV = PV(0x15780b0b0) at 0x157824258
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x6000019a1fe0 "12/21/84 Bob's 21st b'day was a wine-and-dine."
+\0
  CUR = 46
  LEN = 48
  COW_REFCNT = 2
Found words: [12] [21] [84] [bob's] [21st] [b'day] [was] [a] [wine-and
+-dine]
Text: 122184bob's21stb'daywasawine-and-dine
Copy: 122184bob's21stb'daywasawine-and-dine
SV = PV(0x15780b090) at 0x1578242d0
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x6000019a1fe0 "12\x0021\x0084\x00bob's\x0021st\x00b'day\x00was
+\x00a\x00wine-and-dine\x00"\0
  CUR = 46
  LEN = 48
  COW_REFCNT = 2
SV = PV(0x15780b0b0) at 0x157824258
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x6000019a1fe0 "12\x0021\x0084\x00bob's\x0021st\x00b'day\x00was
+\x00a\x00wine-and-dine\x00"\0
  CUR = 46
  LEN = 48
  COW_REFCNT = 2

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