xap_helper_cxx: make the build process ccache-friendly

We need to have stable filenames and separate compilation
from the linkage stage for ccache to hit.  So avoid the use
of a temporary directory and instead rely on a lock file to
guard against parallel builds.

diff --git a/lib/PublicInbox/XapHelperCxx.pm b/lib/PublicInbox/XapHelperCxx.pm
index 0891074d0d31ef8c28c5143c6327601faa57cdf5..7aa5241685957daae22c8596f77a30d5a79b453e 100644 (file)
--- a/lib/PublicInbox/XapHelperCxx.pm
+++ b/lib/PublicInbox/XapHelperCxx.pm
@@ -7,7 +7,7 @@
 # The resulting executable is not linked to Perl in any way.
 package PublicInbox::XapHelperCxx;
 use v5.12;
-use PublicInbox::Spawn qw(run_qx which);
+use PublicInbox::Spawn qw(run_die run_qx which);
 use PublicInbox::IO qw(read_all write_file);
 use PublicInbox::Search;
 use Fcntl qw(SEEK_SET);
@@ -24,8 +24,8 @@ my @pm_dep = map { $srcpfx.$_ } qw(Search.pm CodeSearch.pm);
 my $ldflags = '-Wl,-O1';
 $ldflags .= ' -Wl,--compress-debug-sections=zlib' if $^O ne 'openbsd';
 my $xflags = ($ENV{CXXFLAGS} // '-Wall -ggdb3 -O0') . ' ' .
-       ($ENV{LDFLAGS} // $ldflags) .
-       qq{ -DTHREADID=}.PublicInbox::Search::THREADID;
+       ' -DTHREADID=' . PublicInbox::Search::THREADID .
+       ' ' . ($ENV{LDFLAGS} // $ldflags);
 my $xap_modversion;
 
 sub xap_cfg (@) {
@@ -58,12 +58,12 @@ sub build () {
                die "mkdir($dir): $err" if !-d $dir;
        }
        use autodie;
-       require File::Temp;
        require PublicInbox::CodeSearch;
+       require PublicInbox::Lock;
+       require PublicInbox::OnDestroy;
        my ($prog) = ($bin =~ m!/([^/]+)\z!);
-       my $tmp = File::Temp->newdir(DIR => $dir) // die "newdir: $!";
-       my $src = "$tmp/$prog.cpp";
-       open my $fh, '>', $src;
+       my $lk = PublicInbox::Lock->new("$dir/$prog.lock")->lock_for_scope;
+       open my $fh, '>', "$dir/$prog.cpp";
        for (@srcs) {
                say $fh qq(# line 1 "$_");
                open my $rfh, '<', $_;
@@ -73,6 +73,10 @@ sub build () {
        print $fh PublicInbox::CodeSearch::generate_cxx();
        close $fh;
 
+       opendir my $dh, '.';
+       my $restore = PublicInbox::OnDestroy->new(\&chdir, $dh);
+       chdir $dir;
+
        # xap_modversion may be set by needs_rebuild
        $xap_modversion //= xap_cfg('--modversion');
        my $fl = xap_cfg(qw(--libs --cflags));
@@ -84,14 +88,16 @@ sub build () {
        # distributed packages.
        $^O eq 'netbsd' and $fl =~ s/(\A|[ \t])\-L([^ \t]+)([ \t]|\z)/
                                "$1-L$2 -Wl,-rpath=$2$3"/egsx;
-
-       my $cmd = "$cxx $src $fl $xflags -o $tmp/$prog";
-       system($cmd) and die "$cmd failed: \$?=$?";
-       write_file '>', "$tmp/XFLAGS", $xflags, "\n";
-       write_file '>', "$tmp/xap_modversion", $xap_modversion, "\n";
+       my @xflags = split(/\s+/, "$fl $xflags");
+       my @cflags = grep(!/\A-(?:Wl|l|L)/, @xflags);
+       run_die([$cxx, '-c', "$prog.cpp", @cflags]);
+       run_die([$cxx, '-o', "$prog.tmp", "$prog.o", @xflags]);
+       unlink "$prog.cpp", "$prog.o";
+       write_file '>', 'XFLAGS.tmp', $xflags, "\n";
+       write_file '>', 'xap_modversion.tmp', $xap_modversion, "\n";
        undef $xap_modversion; # do we ever build() twice?
        # not quite atomic, but close enough :P
-       rename("$tmp/$_", "$dir/$_") for ($prog, qw(XFLAGS xap_modversion));
+       rename("$_.tmp", $_) for ($prog, qw(XFLAGS xap_modversion));
 }
 
 sub check_build () {