spawn: improve error checking for fork failures

fork failures are unfortunately common when Xapian has
gigabytes and gigabytes mmapped.

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/PublicInbox/SpawnPP.pm b/lib/PublicInbox/SpawnPP.pm
index 36223e81..179aba5e 100644
--- a/lib/PublicInbox/SpawnPP.pm
+++ b/lib/PublicInbox/SpawnPP.pm
@@ -12,7 +12,12 @@ sub public_inbox_fork_exec ($$$$$$) {
         my $set = POSIX::SigSet->new();
         $set->fillset or die "fillset failed: $!";
         sigprocmask(SIG_SETMASK, $set, $old) or die "can't block signals: $!";
+        my $syserr;
         my $pid = fork;
+        unless (defined $pid) { # compat with Inline::C version
+                $syserr = $!;
+                $pid = -1;
+        }
         if ($pid == 0) {
                 if ($in != 0) {
                         dup2($in, 0) or die "dup2 failed for stdin: $!";
@@ -34,6 +39,7 @@ sub public_inbox_fork_exec ($$$$$$) {
                 }
         }
         sigprocmask(SIG_SETMASK, $old) or die "can't unblock signals: $!";
+        $! = $syserr;
         $pid;
 }