[PATCH 1/2] Makefile.PL: check for execinfo on FreeBSD

[Eric Wong <mwrap-perl@80x24.org>]

This is required for it to work reliably in FreeBSD if we hit a
code path which calls backtrace_symbols before BOOT:.  This will
allow the next commit to setup `totals' rculfhash earlier in the
constructor, rather than BOOT, allowing allocations to be
tracked as early as possible.
---
 Makefile.PL | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/Makefile.PL b/Makefile.PL
index c3caf6c..7ea7929 100644
--- a/Makefile.PL
+++ b/Makefile.PL
@@ -32,6 +32,37 @@ END
 chomp(my $INC = `$pkg_config --cflags liburcu-cds liburcu-bp`);
 my @writemakefile_args = ();
 
+use IO::Handle;
+STDOUT->autoflush(1);
+require ExtUtils::CBuilder;
+require File::Temp;
+my $cb = ExtUtils::CBuilder->new(quiet => $ENV{V} ? 0 : 1);
+my $d = File::Temp->newdir('mwrap-perl-build-XXXX');
+my $olderr;
+print '# checking for -lexecinfo... ';
+{
+	use autodie;
+	open my $fh, '>', "$d/execinfo.c";
+	print $fh <<EOM;
+#include <execinfo.h>
+int main(void) { return backtrace_symbols ? 1 : 0; }
+EOM
+	close $fh;
+	open $olderr, '+>&', *STDERR{IO};
+	open STDERR, '>', "$d/err.log";
+}
+eval {
+	my $obj = $cb->compile(source => "$d/execinfo.c");
+	$cb->link(objects => $obj, extra_linker_flags => '-lexecinfo');
+	$LIBS .= ' -lexecinfo';
+	say " yes on $^O";
+};
+say " no on $^O" if $@;
+{
+	use autodie;
+	open STDERR, '+>&', $olderr or die "dup stderr: $!";
+}
+
 # See lib/ExtUtils/MakeMaker.pm for details of how to influence
 # the contents of the Makefile that is written.
 push @writemakefile_args, (