| Subject: | Win32::API::Struct (v 0.65) and fixed length WCHAR array crashes Perl |
| Date: | Wed, 12 Feb 2014 19:57:10 +0100 |
| To: | bug-Win32-API [...] rt.cpan.org |
| From: | Markus Ortner <markus.ortner [...] utanet.at> |
Dear Daniel and Cosimo,
I was using the impressive Win32::API module to make a call to the
kernel function GetTimeZoneInformation, which is defined as
DWORD GetTimeZoneInformation(LPTIME_ZONE_INFORMATION
lpTimeZoneInformation)
and used Win32::API::Struct (v0.65) to define the TIME_ZONE_INFORMATION
structure:
Win32::API::Struct->typedef( TIME_ZONE_INFORMATION => qw{
LONG Bias;
WCHAR StandardName[32];
SYSTEMTIME StandardDate;
LONG StandardBias;
WCHAR DaylightName[32];
SYSTEMTIME DaylightDate;
LONG DaylightBias;
});
However, Perl crashes when I use following code:
my $tz = Win32::API::Struct->new('TIME_ZONE_INFORMATION');
GetTimeZoneInformation($tz) or die "GetTimeZoneInformation failed:
$^E\n";
I figured out that the root cause of the crash was the packing /
unpacking of the item StandardName (and DaylightName), which is a fixed
length, wide character string of type WCHAR that is 'UTF-16LE' encoded.
This is because Win32::API::Struct::getPack and
Win32::API::Struct::getUnpack do not take the size of the type into
account, but always assume a 8-bit type size (CHAR):
258: if ($type =~ /\w\*(\d+)/) {
259: $repeat = $1;
260: $type = "a$repeat";
261: }
...
350: if ($type =~ /\w\*(\d+)/) {
351: $repeat = $1;
352: $type = "Z$repeat";
353: }
However, for the "$packed_size" the correct value "$type_size * $repeat"
is calculated:
358: $packed_size += ( $type_size * $repeat ) + $type_align;
So, at a first glance I would suggest to use the corrected repeat count
also in line 259 and 351, respectively. Furthermore, getUnpack should
not assume a null-terminated (ASCIZ) string, but a string with arbitrary
binary data as getPack does:
258: if ($type =~ /\w\*(\d+)/) {
259: $repeat = $1**Win32::API::Type::sizeof($orig)*;
260: $type = "a$repeat";
261: }
...
350: if ($type =~ /\w\*(\d+)/) {
351: $repeat = $1**Win32::API::Type::sizeof($orig)*;
352: $type = "*a*$repeat";
353: }
In order to remain compatible, getUnpack may assume a null-terminated
string if and only if the original type is CHAR (or TCHAR). I have not
checked if it is also possible to implement a decoding of a WCHAR that
is encoded as 'UTF-16LE'.
I tested the module with above modifications and it is working fine.
Is it possible to make a correction in a future update of this module to
handle non-CHAR fixed length arrays correctly?
With kind regards,
Markus