Bug#37003 Tests sporadically crashes with embedded server

The problem was that when a embedded linked version of mysqltest
crashed there was no way to obtain a stack trace if no core file
is available. Another problem is that the embedded version of
libmysql was not behaving (crash) the same as the non-embedded with
respect to sending commands to a explicitly closed connection.

The solution is to generate a mysqltest's stack trace on crash
and to enable "reconnect" if the connection handle was explicitly
closed so the behavior matches the non-embedded one.

client/CMakeLists.txt:
  Link mysys to mysqltest.
client/Makefile.am:
  Link mysys to mysqltest.
client/mysqltest.c:
  Add fatal signal handling with backtracing for Unix and Windows.
configure.in:
  Add check for weak symbols support and remove a spurious word.
include/Makefile.am:
  Add new header with prototype for stack tracing functions.
include/my_stacktrace.h:
  Add new header with prototype for stack tracing functions.
libmysqld/CMakeLists.txt:
  stack tracing is now part of mysys.
libmysqld/Makefile.am:
  stack tracing is now part of mysys.
libmysqld/lib_sql.cc:
  Re-connect if connection was explicitly closed. This is
  done to match the behavior of the non-embeded libmysql.
mysql-test/t/sql_low_priority_updates_func.test:
  Test expects parallelism between queries that cannot be
  guaranteed under embedded.
mysys/CMakeLists.txt:
  Add stacktrace to mysys.
mysys/Makefile.am:
  Add stacktrace to mysys.
mysys/stacktrace.c:
  Move stacktrace to mysys and add weak symbol for the
  C++ name de-mangling function so that it can later be
  overridden in C++ code. Also add my_ prefix to exported
  functions.
sql/CMakeLists.txt:
  stacktrace was moved to mysys.
sql/Makefile.am:
  stacktrace was moved to mysys.
sql/mysqld.cc:
  Add my_ prefix to mysys functions.

3 files changed, 11 insertions, 3 deletions

diff --git a/libmysqld/CMakeLists.txt b/libmysqld/CMakeLists.txt
index 97c718627d1..1582f0898d8 100644
--- a/libmysqld/CMakeLists.txt
+++ b/libmysqld/CMakeLists.txt
@@ -185,8 +185,7 @@ SET(LIBMYSQLD_SOURCES emb_qcache.cc libmysqld.c lib_sql.cc
            ../sql/strfunc.cc ../sql/table.cc ../sql/thr_malloc.cc
            ../sql/time.cc ../sql/tztime.cc ../sql/uniques.cc ../sql/unireg.cc
            ../sql/partition_info.cc ../sql/sql_connect.cc 
-           ../sql/scheduler.cc ../sql/stacktrace.c
-           ../sql/event_parse_data.cc
+           ../sql/scheduler.cc ../sql/event_parse_data.cc
            ${GEN_SOURCES}
            ${LIB_SOURCES})
 
diff --git a/libmysqld/Makefile.am b/libmysqld/Makefile.am
index 504980cbd07..ef2fab2da6d 100644
--- a/libmysqld/Makefile.am
+++ b/libmysqld/Makefile.am
@@ -69,7 +69,7 @@ sqlsources = derror.cc field.cc field_conv.cc strfunc.cc filesort.cc \
 	sql_select.cc sql_do.cc sql_show.cc set_var.cc \
 	sql_string.cc sql_table.cc sql_test.cc sql_udf.cc \
 	sql_update.cc sql_yacc.cc table.cc thr_malloc.cc time.cc \
-	unireg.cc uniques.cc stacktrace.c sql_union.cc hash_filo.cc \
+	unireg.cc uniques.cc sql_union.cc hash_filo.cc \
 	spatial.cc gstream.cc sql_help.cc tztime.cc sql_cursor.cc \
 	sp_head.cc sp_pcontext.cc sp.cc sp_cache.cc sp_rcontext.cc \
 	parse_file.cc sql_view.cc sql_trigger.cc my_decimal.cc \
diff --git a/libmysqld/lib_sql.cc b/libmysqld/lib_sql.cc
index 591b76f61ad..e1c8ab5abb4 100644
--- a/libmysqld/lib_sql.cc
+++ b/libmysqld/lib_sql.cc
@@ -79,6 +79,15 @@ emb_advanced_command(MYSQL *mysql, enum enum_server_command command,
   my_bool result= 1;
   THD *thd=(THD *) mysql->thd;
   NET *net= &mysql->net;
+  my_bool stmt_skip= stmt ? stmt->state != MYSQL_STMT_INIT_DONE : FALSE;
+
+  if (!thd)
+  {
+    /* Do "reconnect" if possible */
+    if (mysql_reconnect(mysql) || stmt_skip)
+      return 1;
+    thd= (THD *) mysql->thd;
+  }
 
 #if defined(ENABLED_PROFILING) && defined(COMMUNITY_SERVER)
   thd->profiling.start_new_query();