[PATCH][analyzer] Prevent ccc/c++-analyzer from hanging on Windows.

[Anton Yartsev]

Ping!

Attached are an updated patch for ccc-analyzer and a similar patch for 
scan-build, please review.

> On 06.11.2014 20:27, Jordan Rose wrote:
>> I think my point was "why bother forking at all if we're using open 
>> to run a subprocess?".
> Ah, got it! Attached is an updated patch.
>
>>
>> Also, this will fail if the path contains spaces:
> Corrected.
>
>>
>> +    my $ExecLine = join(' ', $Clang, "-###", $mode, @$Args, "2>&1", 
>> "|");
>> +    open(PS, $ExecLine);
>>
>> Do newer Perls on newer Windows support the list form of open?
> No, at least ActivePerl, StrawberryPerl and Dwimperl.
>
> Current perl docs state:
> 'open to ||-| and |-|| are unsupported. (Win32, RISC OS)' 
> (http://perldoc.perl.org/perlport.html#open)
> and
> 'The open(FOO, "|-") and open(BAR, "-|") constructs are not yet 
> implemented.' (http://perldoc.perl.org/perlfork.html)
>
>> Jordan
>>
>>
>>> On Nov 5, 2014, at 11:54 , Anton Yartsev <anton.yartsev at gmail.com 
>>> <mailto:anton.yartsev at gmail.com>> wrote:
>>>
>>> Ping!
>>>> 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 <http://cpan.org>, but they are not guarantee 
>>>> to be included at the users perl distribution.
>>>>> 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?
>>>>>
>>>>> Jordan
>>>>>
>>>>>
>>>>> On Oct 21, 2014, at 6:47 , Anton Yartsev <anton.yartsev at gmail.com 
>>>>> <mailto:anton.yartsev at gmail.com>> wrote:
>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> Attached is the patch that prevents ccc/c++-analyzer from hang if 
>>>>>> launched with ActivePerl or Strawberry Perl interpreters.
>>>>>> 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.
>>>>>> The conditions for hang are: child should open a pipe to the 
>>>>>> parent and parent should read from the child, otherwise no hang.
>>>>>>
>>>>>> The problem is possibly caused by the bug in emulation of 'fork' 
>>>>>> by Perl interpreters on Windows. From perlfork 
>>>>>> <http://perldoc.perl.org/perlfork.html> documentation, BUGS section:
>>>>>> "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."
>>>>>>
>>>>>> An example from perlfork documentation also hangs:
>>>>>>
>>>>>> # simulate open(FOO, "-|")
>>>>>> sub pipe_from_fork ($) {
>>>>>>     my $parent = shift;
>>>>>>     pipe $parent, my $child or die;
>>>>>>     my $pid = fork();
>>>>>>     die "fork() failed: $!" unless defined $pid;
>>>>>>     if ($pid) {
>>>>>>       close $child;
>>>>>>     }
>>>>>>     else {
>>>>>>       close $parent;
>>>>>>       open(STDOUT, ">&=" . fileno($child)) or die;
>>>>>>     }
>>>>>>   $pid;
>>>>>> }
>>>>>>
>>>>>> if (pipe_from_fork('BAR')) {
>>>>>> # parent
>>>>>> while (<BAR>) { print; }
>>>>>>   close BAR;
>>>>>> }
>>>>>> else {
>>>>>>   # child
>>>>>>   print "pipe_from_fork\n";
>>>>>>   exit(0);
>>>>>> }
>>>>>>
>>>>>> The hang is not reproduced only with the MSYS Perl.
>>>>>>
>>>>>> OK to commit?
>>>>>> -- 
>>>>>> Anton
>>>>>> <ccc-analyzer_fork_open_hang.patch>
>>>>>
>>>>
>>>>
>>>> -- 
>>>> Anton
>>>
>>>
>>> -- 
>>> Anton
>>
>
>
> -- 
> Anton


-- 
Anton

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