Add a workaround for broken MariaDB clients which overwrite SIGPIPE h…

…andler

MariaDB Connector/C 3.0.0 in function mysql_server_init() for non-Windows
systems started setting SIGPIPE handler to SIG_IGN. This breaks Perl
applications which installed its own SIGPIPE signal handler.

As a workaround use Perl rsignal_save() function to save existing SIGPIPE
handler before calling mysql_server_init() and after that restore saved
handler via Perl rsignal_restore() function.

Add a test which verifies that DBI->connect() which calls DBD::MariaDB's
mariadb_dr_connect() function and which calls mysql_server_init(), does not
overwrite $SIG{PIPE} handler set in Perl code.

Fixes: perl5-dbi#170
See: http://jira.mariadb.org/browse/CONC-591

MANIFEST

@@ -23,6 +23,7 @@ t/15reconnect.t
 t/16dbi-get_info.t
 t/17close_on_exec.t
 t/18begin_work_without_raise_error.t
+t/19sigpipe.t
 t/20createdrop.t
 t/25lockunlock.t
 t/29warnings.t

dbdimp.c

@@ -1643,9 +1643,32 @@ static bool mariadb_dr_connect(
   {
     if (imp_drh->instances == 0 && !imp_drh->non_embedded_started)
     {
+      int init_failed;
+
+      /*
+       * MariaDB Connector/C 3.0.0 in function mysql_server_init() for non-Windows systems started
+       * setting SIGPIPE handler to SIG_IGN. This breaks Perl applications which installed its own
+       * SIGPIPE signal handler. As a workaround use Perl rsignal_save() function to save existing
+       * SIGPIPE handler before calling mysql_server_init() and after that restore saved handler via
+       * Perl rsignal_restore() function. Note that Perl rsignal_save() function overwrites current
+       * handler (to our specified SIG_IGN), but this is not an issue as we always restored the
+       * saved handler. See reported issue: http://jira.mariadb.org/browse/CONC-591
+       */
+#if !defined(_WIN32) && defined(SIGPIPE) && defined(MARIADB_PACKAGE_VERSION) && defined(MARIADB_PACKAGE_VERSION_ID) && MARIADB_PACKAGE_VERSION_ID >= 30000
+      Sigsave_t pipehand;
+      int pipehand_failed = Perl_rsignal_save(aTHX_ SIGPIPE, (Sighandler_t)(void (*)())SIG_IGN, &pipehand);
+#endif
+
       /* negative value means to not start embedded server and just to initialize client library */
       /* initializing client library is needed prior to any other mysql_* call from client library */
-      if (mysql_server_init(-1, NULL, NULL))
+      init_failed = mysql_server_init(-1, NULL, NULL);
+
+#if !defined(_WIN32) && defined(SIGPIPE) && defined(MARIADB_PACKAGE_VERSION) && defined(MARIADB_PACKAGE_VERSION_ID) && MARIADB_PACKAGE_VERSION_ID >= 30000
+      if (!pipehand_failed)
+        Perl_rsignal_restore(aTHX_ SIGPIPE, &pipehand);
+#endif
+
+      if (init_failed)
       {
         error_no_connection(dbh, "Connection error: Cannot initialize client library");
         return FALSE;

t/19sigpipe.t

@@ -0,0 +1,22 @@
+use strict;
+use warnings;
+
+use Test::More;
+use DBI;
+
+use vars qw($test_dsn $test_user $test_password);
+use lib 't', '.';
+require 'lib.pl';
+
+plan skip_all => '$SIG{PIPE} is not supported' unless exists $SIG{PIPE};
+
+plan tests => 1;
+
+my $sigpipe_handler_called;
+$SIG{PIPE} = sub { $sigpipe_handler_called = 1; };
+
+DBI->connect($test_dsn, $test_user, $test_password, { RaiseError => 0, PrintError => 0, AutoCommit => 0 });
+
+kill('PIPE', $$);
+
+ok($sigpipe_handler_called, 'DBI->connect() does not overwrite $SIG{PIPE} handler');