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
Index: ccc-analyzer
===================================================================
--- ccc-analyzer (revision 218624)
+++ ccc-analyzer (working copy)
@@ -154,9 +154,12 @@
my $pid = fork();
if ($pid == 0) {
close FROM_CHILD;
- open(STDOUT,">&", \*TO_PARENT);
- open(STDERR,">&", \*TO_PARENT);
- exec $Clang, "-###", $mode, @$Args;
+ my $ExecLine = join(' ', $Clang, "-###", $mode, @$Args, "2>&1", "|");
+ open(PS, $ExecLine);
+ while ( <PS> ) {
+ print TO_PARENT $_;
+ }
+ exit;
}
close(TO_PARENT);
my $line;
@@ -255,9 +258,12 @@
my $pid = fork();
if ($pid == 0) {
close FROM_CHILD;
- open(STDOUT,">&", \*TO_PARENT);
- open(STDERR,">&", \*TO_PARENT);
- exec $Cmd, @CmdArgs;
+ my $ExecLine = join(' ', $Cmd, @CmdArgs, "2>&1", "|");
+ open(PS, $ExecLine);
+ while ( <PS> ) {
+ print TO_PARENT $_;
+ }
+ exit;
}
close TO_PARENT;
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