IPC::Open3 handled exec failure badly

When you're in the child, don't croak - you may get trapped by
eval. Also clarify the documentation

p4raw-id: //depot/perl@28347

diff --git a/lib/IPC/Open3.pm b/lib/IPC/Open3.pm
index 084cd33..ba41733 100644 (file)
--- a/lib/IPC/Open3.pm
+++ b/lib/IPC/Open3.pm
@@ -51,8 +51,12 @@ as file descriptors.
 
 open3() returns the process ID of the child process.  It doesn't return on
 failure: it just raises an exception matching C</^open3:/>.  However,
-C<exec> failures in the child are not detected.  You'll have to 
-trap SIGPIPE yourself.
+C<exec> failures in the child (such as no such file or permission denied),
+are just reported to CHLD_ERR, as it is not possible to trap them.
+
+If the child process dies for any reason, the next write to CHLD_IN is
+likely to generate a SIGPIPE in the parent, which is fatal by default.
+So you may wish to handle this signal.
 
 Note if you specify C<-> as the command, in an analogous fashion to
 C<open(FOO, "-|")> the child process will just be the forked Perl
@@ -83,6 +87,21 @@ over source code being run in the child process, you can't control
 what it does with pipe buffering.  Thus you can't just open a pipe to
 C<cat -v> and continually read and write a line from it.
 
+=head1 See Also
+
+=over 4
+
+=item L<IPC::Open2>
+
+Like Open3 but without STDERR catpure.
+
+=item L<IPC::Run>
+
+This is a CPAN module that has better error handling and more facilities
+than Open3.
+
+=back
+
 =head1 WARNING
 
 The order of arguments differs from that of open2().
@@ -164,6 +183,10 @@ sub _open3 {
     my($package, $dad_wtr, $dad_rdr, $dad_err, @cmd) = @_;
     my($dup_wtr, $dup_rdr, $dup_err, $kidpid);
 
+    if (@cmd > 1 and $cmd[0] eq '-') {
+       croak "Arguments don't make sense when the command is '-'"
+    }
+
     # simulate autovivification of filehandles because
     # it's too ugly to use @_ throughout to make perl do it for us
     # tchrist 5-Mar-00
@@ -237,14 +260,9 @@ sub _open3 {
        } else {
            xopen \*STDERR, ">&STDOUT" if fileno(STDERR) != fileno(STDOUT);
        }
-       if ($cmd[0] eq '-') {
-           croak "Arguments don't make sense when the command is '-'"
-             if @cmd > 1;
-           return 0;
-       }
+       return 0 if ($cmd[0] eq '-');
        local($")=(" ");
-       exec @cmd # XXX: wrong process to croak from
-           or croak "$Me: exec of @cmd failed";
+       exec @cmd or do { carp "$Me: exec of @cmd failed"; exit 255; };
     } elsif ($do_spawn) {
        # All the bookkeeping of coincidence between handles is
        # handled in spawn_with_handles.