spawn+gcf2: improve diagnostics for build failures

I'm not sure why, but I noticed the one of my latest restarts of
public-inbox-httpd wasn't loading the Inline::C .so for Gcf2 nor
Spawn.  I also can't reproduce the problem as both .so files are
loaded fine on a restart with zero config changes.

In any case, some extra, automatic diagnostics for build errors
won't hurt, as no extra noise is introduced for successful builds.
This will also make future development of C code more convenient,
hopefully.

1 files changed, 26 insertions, 13 deletions

diff --git a/lib/PublicInbox/Gcf2.pm b/lib/PublicInbox/Gcf2.pm
index 0f967579..0d31b014 100644
--- a/lib/PublicInbox/Gcf2.pm
+++ b/lib/PublicInbox/Gcf2.pm
@@ -7,16 +7,16 @@ package PublicInbox::Gcf2;
 use strict;
 use v5.10.1;
 use PublicInbox::Spawn qw(which popen_rd); # may set PERL_INLINE_DIRECTORY
-use Fcntl qw(LOCK_EX);
+use Fcntl qw(LOCK_EX SEEK_SET);
 use IO::Handle; # autoflush
-my (%CFG, $c_src, $lockfh);
 BEGIN {
+        my (%CFG, $c_src);
         # PublicInbox::Spawn will set PERL_INLINE_DIRECTORY
         # to ~/.cache/public-inbox/inline-c if it exists
         my $inline_dir = $ENV{PERL_INLINE_DIRECTORY} //
                 die 'PERL_INLINE_DIRECTORY not defined';
         my $f = "$inline_dir/.public-inbox.lock";
-        open $lockfh, '>', $f or die "failed to open $f: $!\n";
+        open my $fh, '+>', $f or die "open($f): $!";
         my $pc = which($ENV{PKG_CONFIG} // 'pkg-config') //
                 die "pkg-config missing for libgit2";
         my ($dir) = (__FILE__ =~ m!\A(.+?)/[^/]+\z!);
@@ -37,27 +37,40 @@ BEGIN {
                 if (open(my $fh, '<', $f)) {
                         chomp($l, $c);
                         local $/;
-                        defined($c_src = <$fh>) or die "read $f: $!\n";
+                        defined($c_src = <$fh>) or die "read $f: $!";
                         $CFG{LIBS} = $l;
                         $CFG{CCFLAGSEX} = $c;
                         last;
                 } else {
-                        die "E: $f: $!\n";
+                        die "E: $f: $!";
                 }
         }
         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: $!";
+        open STDERR, '>&', $fh or die "2>$f: $!";
+        STDERR->autoflush(1);
+        STDOUT->autoflush(1);
+
         # CentOS 7.x ships Inline 0.53, 0.64+ has built-in locking
-        flock($lockfh, LOCK_EX) or die "LOCK_EX failed on $f: $!\n";
+        flock($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 = $@;
+        open(STDERR, '>&', $olderr) or warn "restore stderr: $!";
+        open(STDOUT, '>&', $oldout) or warn "restore stdout: $!";
+        if ($err) {
+                seek($fh, 0, SEEK_SET);
+                my @msg = <$fh>;
+                die "Inline::C Gcf2 build failed:\n", $err, "\n", @msg;
+        }
 }
 
-# we use Capitalized and ALLCAPS for compatibility with old Inline::C
-use Inline C => Config => %CFG, BOOT => 'git_libgit2_init();';
-use Inline C => $c_src;
-undef $c_src;
-undef %CFG;
-undef $lockfh;
-
 sub add_alt ($$) {
         my ($gcf2, $objdir) = @_;