gcf2: fix loading at runtime

We need to waitpid synchronously on pkg-config to use $?.

When loading Gcf2 inside the event loop, implicit dwaitpid
done by PublicInbox::ProcessPipe would not call waitpid in
time to zero $?.  This was causing one of my -httpd to
occasionally fall back to git(1) instead of using Gcf2.

This was noted in:
Link: https://public-inbox.org/meta/20210914085322.25517-1-e@80x24.org/

diff --git a/lib/PublicInbox/Gcf2.pm b/lib/PublicInbox/Gcf2.pm
index 0d31b01462a7dfb486f5e6f072bc248fc5a3c363..64945ca69cff7fa3cec96539fad0ac0a8f9bfe9d 100644 (file)
--- a/lib/PublicInbox/Gcf2.pm
+++ b/lib/PublicInbox/Gcf2.pm
@@ -17,36 +17,43 @@ BEGIN {
                die 'PERL_INLINE_DIRECTORY not defined';
        my $f = "$inline_dir/.public-inbox.lock";
        open my $fh, '+>', $f or die "open($f): $!";
+
+       # CentOS 7.x ships Inline 0.53, 0.64+ has built-in locking
+       flock($fh, LOCK_EX) or die "LOCK_EX($f): $!\n";
+
        my $pc = which($ENV{PKG_CONFIG} // 'pkg-config') //
                die "pkg-config missing for libgit2";
        my ($dir) = (__FILE__ =~ m!\A(.+?)/[^/]+\z!);
-       my $rdr = {};
-       open $rdr->{2}, '>', '/dev/null' or die "open /dev/null: $!";
+       my $ef = "$inline_dir/.public-inbox.pkg-config.err";
+       open my $err, '+>', $ef or die "open($ef): $!";
        for my $x (qw(libgit2)) {
-               my $l = popen_rd([$pc, '--libs', $x], undef, $rdr);
+               my $rdr = { 2 => $err };
+               my ($l, $pid) = popen_rd([$pc, '--libs', $x], undef, $rdr);
                $l = do { local $/; <$l> };
+               waitpid($pid, 0);
                next if $?;
-               my $c = popen_rd([$pc, '--cflags', $x], undef, $rdr);
+               (my $c, $pid) = popen_rd([$pc, '--cflags', $x], undef, $rdr);
                $c = do { local $/; <$c> };
+               waitpid($pid, 0);
                next if $?;
 
                # note: we name C source files .h to prevent
                # ExtUtils::MakeMaker from automatically trying to
                # build them.
                my $f = "$dir/gcf2_$x.h";
-               if (open(my $fh, '<', $f)) {
-                       chomp($l, $c);
-                       local $/;
-                       defined($c_src = <$fh>) or die "read $f: $!";
-                       $CFG{LIBS} = $l;
-                       $CFG{CCFLAGSEX} = $c;
-                       last;
-               } else {
-                       die "E: $f: $!";
-               }
+               open(my $src, '<', $f) or die "E: open($f): $!";
+               chomp($l, $c);
+               local $/;
+               defined($c_src = <$src>) or die "read $f: $!";
+               $CFG{LIBS} = $l;
+               $CFG{CCFLAGSEX} = $c;
+               last;
+       }
+       unless ($c_src) {
+               seek($err, 0, SEEK_SET);
+               $err = do { local $/; <$err> };
+               die "E: libgit2 not installed: $err\n";
        }
-       die "E: libgit2 not installed\n" unless $c_src;
-
        open my $oldout, '>&', \*STDOUT or die "dup(1): $!";
        open my $olderr, '>&', \*STDERR or die "dup(2): $!";
        open STDOUT, '>&', $fh or die "1>$f: $!";
@@ -54,14 +61,12 @@ BEGIN {
        STDERR->autoflush(1);
        STDOUT->autoflush(1);
 
-       # CentOS 7.x ships Inline 0.53, 0.64+ has built-in locking
-       flock($fh, LOCK_EX) or die "LOCK_EX($f): $!\n";
        # we use Capitalized and ALLCAPS for compatibility with old Inline::C
        eval <<'EOM';
 use Inline C => Config => %CFG, BOOT => q[git_libgit2_init();];
 use Inline C => $c_src, BUILD_NOISY => 1;
 EOM
-       my $err = $@;
+       $err = $@;
        open(STDERR, '>&', $olderr) or warn "restore stderr: $!";
        open(STDOUT, '>&', $oldout) or warn "restore stdout: $!";
        if ($err) {