new interface for creating uninitalized or zero stat objects

Author: plicease

Changes

@@ -1,6 +1,12 @@
 Revision history for {{$dist->name}}
 
 {{$NEXT}}
+  - Passing no arguments to new will now return an
+    uninitialized stat object (gh#9, gh#10)
+  - Passing undef to clone will now return a stat
+    object with the memory set to all zeros,
+    previously the behavior was undefined and could
+    crash (gh#10)
 
 0.02      2021-05-31 05:48:05 -0600
   - Work around possible bug in Perl stat function

README.md

@@ -46,10 +46,12 @@ $ffi->attach( my_cfunction => ['stat'] => 'void' );
 ```perl
 my $stat = FFI::C::Stat->new(*HANDLE,   %options);
 my $stat = FFI::C::Stat->new($filename, %options);
+my $stat = FFI::C::Stat->new;
 ```
 
 You can create a new instance of this class by calling the new method and passing in
-either a file or directory handle, or by passing in the filename path.
+either a file or directory handle, or by passing in the filename path.  If you do
+not pass anything then an uninitialized stat will be returned.
 
 Options:
 
@@ -91,6 +93,10 @@ $ffi->attach( my_cfunction => [] => 'opaque' => sub {
 });
 ```
 
+The behavior of passing in `undef` prior to version 0.03 was undefined and could cause a
+crash.  In version 0.03 and later passing in `undef` will return a stat object with all
+of the bits set to zero (0).
+
 # PROPERTIES
 
 ## dev
@@ -203,7 +209,7 @@ Graham Ollis <[email protected]>
 
 # COPYRIGHT AND LICENSE
 
-This software is copyright (c) 2021 by Graham Ollis.
+This software is copyright (c) 2021-2023 by Graham Ollis.
 
 This is free software; you can redistribute it and/or modify it under
 the same terms as the Perl 5 programming language system itself.

dist.ini

@@ -2,7 +2,7 @@ name             = FFI-C-Stat
 author           = Graham Ollis <[email protected]>
 license          = Perl_5
 copyright_holder = Graham Ollis
-copyright_year   = 2021-2022
+copyright_year   = 2021-2023
 version          = 0.02
 
 [@Author::Plicease]

ffi/stat.c

@@ -54,12 +54,27 @@ stat___fstat(int fd)
 }
 
 struct stat *
-stat__clone(struct stat *self)
+stat___new(void)
 {
-  struct stat *other;
-  other = malloc(sizeof(struct stat));
-  memcpy(other, self, sizeof(struct stat));
-  return other;
+  struct stat *self;
+  self = malloc(sizeof(struct stat));
+  return self;
+}
+
+struct stat *
+stat__clone(struct stat *other)
+{
+  struct stat *self;
+  self = malloc(sizeof(struct stat));
+  if(other == NULL)
+  {
+    memset(self, 0, sizeof(struct stat));
+  }
+  else
+  {
+    memcpy(self, other, sizeof(struct stat));
+  }
+  return self;
 }
 
 dev_t

lib/FFI/C/Stat.pm

@@ -54,16 +54,19 @@ $ffi->mangler(sub { "stat__$_[0]" });
 $ffi->attach( '_stat'  => ['string'] => 'opaque' );
 $ffi->attach( '_fstat' => ['int',  ] => 'opaque' );
 $ffi->attach( '_lstat' => ['string'] => 'opaque' );
+$ffi->attach( '_new'   => []         => 'opaque' );
 
 =head1 CONSTRUCTORS
 
 =head2 new
 
  my $stat = FFI::C::Stat->new(*HANDLE,   %options);
  my $stat = FFI::C::Stat->new($filename, %options);
+ my $stat = FFI::C::Stat->new;
 
 You can create a new instance of this class by calling the new method and passing in
-either a file or directory handle, or by passing in the filename path.
+either a file or directory handle, or by passing in the filename path.  If you do
+not pass anything then an uninitialized stat will be returned.
 
 Options:
 
@@ -87,6 +90,8 @@ sub new
   { $ptr = _fstat(fileno($file)) }
   elsif(!is_ref($file) && defined $file)
   { $ptr = $options{symlink} ? _lstat($file) : _stat($file) }
+  elsif(!defined $file)
+  { $ptr = _new() }
   else
   { Carp::croak("Tried to stat something whch is neither a glob reference nor a plain string") }
 
@@ -120,6 +125,10 @@ Perl:
    return FFI::C::Stat->clone($ptr);
  });
 
+The behavior of passing in C<undef> prior to version 0.03 was undefined and could cause a
+crash.  In version 0.03 and later passing in C<undef> will return a stat object with all
+of the bits set to zero (0).
+
 =cut
 
 $ffi->attach( clone => ['opaque'] => 'opaque' => sub {

t/ffi_c_stat.t

@@ -71,6 +71,15 @@ is(
   'clone a stat',
 );
 
+is(
+  FFI::C::Stat->clone(undef),
+  object {
+    call [ isa => 'FFI::C::Stat' ] => T();
+    call $_ => D() for @props;
+  },
+  'clone undef',
+);
+
 {
   my $other = FFI::C::Stat->new('corpus/xx.txt');
   is(
@@ -122,4 +131,13 @@ if($Config{d_symlink} eq 'define')
 
 unlink 'testlink';
 
+is(
+  FFI::C::Stat->new,
+  object {
+    call [ isa => 'FFI::C::Stat' ] => T();
+    call $_ => D() for @props;
+  },
+  'create uninitalized stat',
+);
+
 done_testing;