http://www.perlmonks.org?node_id=1048613


in reply to Really Odd Bug With LWP and Device::SerialPort

What version of perl? On 5.8.8, I get:
use strict;
use warnings;

my $url='https://github.com';
use LWP::UserAgent;
use Encode qw(is_utf8);
use Data::Dumper;

my $useragent = LWP::UserAgent->new();
my $request = new HTTP::Request;
$request->method("GET");
$request->url($url);
my $response = $useragent->request($request);

my $data = $response->decoded_content();
print "1: ",is_utf8($data),"\n";
$data = substr($data,0);
print "2: ",is_utf8($data),"\n";

# Prints:
1: 1
2:

[download]
On 5.14, I get:
1: 1
2: 1

[download]

Replies are listed 'Best First'.
Re^2: Really Odd Bug With LWP and Device::SerialPort
by kschwab (Vicar) on Aug 08, 2013 at 18:02 UTC
    5.14.12 on the debian box, 5.16.2 on windows. My customer has the raspbian machine, so I'm not sure what version for them. On both machines above (which both show the bug), your code prints: 
    1: 1
2: 1

    [download]
    So, if the idea was that making the data non-utf8 was the cure, that doesn't seem to be it.
[reply]
[d/l]

      Well, there is some differences in the 'MAGIC' attributes before and after the substr (no MAGIC before, but MAGIC after) when you do Devel::Peek::Dump($data), but I don't know enough about that stuff to know what it means (non-magic unicode strings don't work with serial ports?).

      This appears after the substr:

        MAGIC = 0x6336a0
    MG_VIRTUAL = &PL_vtbl_utf8
    MG_TYPE = PERL_MAGIC_utf8(w)
    MG_LEN = -1

      [download]

      I would think that you might want to specify the encoding when writing to a serial port though.

      Update: Sounds somewhat similar to this issue?

[reply]
[d/l]
[select]
        Going down that line, the bug isn't triggered when pulling from an http:// url, but it IS triggered with an https:// (ssl) url. The output from Devel::Peek::Dump looks pretty much identical. Which I suppose means the answer isn't anywhere in MAGIC or utf8. Thanks for the pointers though. 
        # Devel::Peek::Dump output with https url (triggers bug)
SV = PVMG(0x2fbcc3c) at 0x25e7ff4
  REFCNT = 1
  FLAGS = (PADMY,SMG,POK,pPOK,UTF8)
  IV = 0
  NV = 0
  PV = 0x2ff7034 "<!DOCT"\0 [UTF8 "<!DOCT"]
  CUR = 6
  LEN = 12
  MAGIC = 0x2f9066c
    MG_VIRTUAL = &PL_vtbl_mglob
    MG_TYPE = PERL_MAGIC_regex_global(g)
    MG_LEN = -1

# Devel::Peek::Dump output with http url (doesn't trigger bug)
SV = PVMG(0x2e25434) at 0x2567ff4
  REFCNT = 1
  FLAGS = (PADMY,SMG,POK,pPOK,UTF8)
  IV = 0
  NV = 0
  PV = 0x2fe7c5c "<!DOCT"\0 [UTF8 "<!DOCT"]
  CUR = 6
  LEN = 12
  MAGIC = 0x2d96af4
    MG_VIRTUAL = &PL_vtbl_mglob
    MG_TYPE = PERL_MAGIC_regex_global(g)
    MG_LEN = -1

        [download]
[reply]
[d/l]

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