check defined return value for localized slurp errors

Reading from regular files (even on STDIN) can fail
when dealing with flakey storage.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/PublicInbox/Gcf2.pm b/lib/PublicInbox/Gcf2.pm
index 041dffe7..fe6afef2 100644
--- a/lib/PublicInbox/Gcf2.pm
+++ b/lib/PublicInbox/Gcf2.pm
@@ -35,7 +35,7 @@ BEGIN {
                 if (open(my $fh, '<', $f)) {
                         chomp($l, $c);
                         local $/;
-                        $c_src = <$fh>;
+                        defined($c_src = <$fh>) or die "read $f: $!\n";
                         $CFG{LIBS} = $l;
                         $CFG{CCFLAGSEX} = $c;
                         last;