"ReadKey" deadlocks with latest StrawberryPerl

[amba]

If you give ReadKey an argument between 0 and 1, it hangs forever.

This was working fine with StrawberryPerl 5.20.1.1.

Code:

use 5.020;
use warnings;
use strict;

use Term::ReadKey;

warn "Version: $Term::ReadKey::VERSION \n";
    
my $x = ReadKey(1e-5);

warn "x: $x";

You can reproduce this easily, even without a windows installation, using the following Appveyor build script: (See a recent blog post of eserte)

install:
  - choco install strawberryperl
  - path C:\strawberry\perl\bin;C:\strawberry\perl\site\bin;C:\strawberry\c\bin;%PATH%
  - perl -V
  
build_script:
  - perl term-readkey.pl

See https://ci.appveyor.com/project/amba/term-readkey-windows/build/1.0.3 for the full build log.

[jonathanstowe]

I can't easily fix it without a windows installation, this does look somewhat like a bug in StrawberryPerl.

I think the best I will be able to do is treat 0 > $ < 1 as 1

[amba]

I've opened a StrawberryPerl bug:
https://rt.cpan.org/Public/Bug/Display.html?id=120043

[jonathanstowe]

It may be useful if you could paste the generated verision of the ReadKey from the installed ReadKey.pm as it's not clear which one would be used with SP :)

[amba]

The Strawberry Perl upstream's response to my report:

On a MSWin32 ReadKey function looks like this:

sub ReadKey {
my $File = normalizehandle((@>1?$[1]:*STDIN));
if ($[0] || $CurrentMode >= 3) {
Win32PeekChar($File, $[0]);
} else {
getc $File;
}
}

where Win32PeekChar looks like this:

SV * Win32PeekChar(file, delay)
InputStream file
U32 delay <<<<<<<<<<<<<<<<< the trouble!!!
CODE:
{
char key;
if (Win32PeekChar(aTHX_ file, delay, &key))
RETVAL = newSVpv(&key, 1);
else
RETVAL = newSVsv(&PL_sv_undef);
}
OUTPUT:
RETVAL

So calling something like this:

my $x = ReadKey(1e-5);

means that the delay value 1e-5 is converted to U32 (unsigned 32bit integer) which I guess would be 0 (zero), therefore the same as calling my $x = ReadKey(0) - which is exactly what it does (blocking read waiting till you hit any key).

As for the versions:

• Strawberry Perl 5.20.1.1 has TermReadKey-2.31
• Strawberry Perl 5.24.1.1 has TermReadKey-2.37

And if you compare 2.31 vs. 2.37 you will find:

-int Win32PeekChar(PerlIO *file,double delay,char *key)
+int Win32PeekChar(pTHX_ PerlIO *file,U32 delay,char *key)

Note "double delay" vs. "U32 delay"

Full diff:
https://metacpan.org/diff/file?target=JSTOWE%2FTermReadKey-2.37%2F&amp;source=JSTOWE%2FTermReadKey-2.31

So IMHO definitely not a bug Strawberry Perl. ReadKey's Win32PeekChar needs a fix.

[jonathanstowe]

I'll need to check why that was changed like that in the first place.

[amba]

Thanks for the merge!