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<div class="moz-cite-prefix">Ping!<br>
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<blockquote cite="mid:5452879E.5080509@Gmail.com" type="cite">
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<div class="moz-cite-prefix">It seems that fork is the only native
perl mean for creating subprocesses. There is a number of
packages that provide means for spawning at cpan.org, but they
are not guarantee to be included at the users perl distribution.</div>
<blockquote
cite="mid:658A0B49-9795-4D6E-AA12-363D7CD99B02@apple.com"
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<div>Looking at this code, it's weird that we're doing this as a
fork/exec (or not-exec) at all. Why can't we just spawn a
sub-process?</div>
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<div>Jordan</div>
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<br>
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<div>On Oct 21, 2014, at 6:47 , Anton Yartsev <<a
moz-do-not-send="true"
href="mailto:anton.yartsev@gmail.com">anton.yartsev@gmail.com</a>>
wrote:</div>
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<div bgcolor="#FFFFFF" text="#000000"> Hi all,<br>
<br>
Attached is the patch that prevents ccc/c++-analyzer from
hang if launched with ActivePerl or Strawberry Perl
interpreters.<br>
The patch replaces the code that creates a pipe from child
to parent to the more portable explicit writing to parent,
this prevent interpreters from hang.<br>
The conditions for hang are: child should open a pipe to
the parent and parent should read from the child,
otherwise no hang.<br>
<br>
The problem is possibly caused by the bug in emulation of
'fork' by Perl interpreters on Windows. From <a
moz-do-not-send="true"
href="http://perldoc.perl.org/perlfork.html">perlfork</a>
documentation, BUGS section:<br>
"In certain cases, the OS-level handles created by the
pipe(), socket(), and accept() operators are apparently
not duplicated accurately in pseudo-processes. This only
happens in some situations, but where it does happen, it
may result in deadlocks between the read and write ends of
pipe handles, or inability to send or receive data across
socket handles."<br>
<br>
An example from perlfork documentation also hangs:<br>
<br>
# simulate open(FOO, "-|")<br>
sub pipe_from_fork ($) {<br>
my $parent = shift;<br>
pipe $parent, my $child or die;<br>
my $pid = fork();<br>
die "fork() failed: $!" unless defined $pid;<br>
if ($pid) {<br>
close $child;<br>
}<br>
else {<br>
close $parent;<br>
open(STDOUT, ">&=" . fileno($child)) or die;<br>
}<br>
$pid;<br>
}<br>
<br>
if (pipe_from_fork('BAR')) {<br>
# parent<br>
while (<BAR>) { print; }<br>
close BAR;<br>
}<br>
else {<br>
# child<br>
print "pipe_from_fork\n";<br>
exit(0);<br>
}<br>
<br>
The hang is not reproduced only with the MSYS Perl.<br>
<br>
OK to commit?<br>
<pre class="moz-signature" cols="72">--
Anton</pre>
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<span><ccc-analyzer_fork_open_hang.patch></span></blockquote>
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<br>
<br>
<pre class="moz-signature" cols="72">--
Anton</pre>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Anton</pre>
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