Bug#32757: hang with sql_mode set when setting some global variables

If setting a system-variable provided by a plug-in failed, no OK or
error was sent in some cases, hanging the client. We now send an error
in the case from the ticket (integer-argument out of range in STRICT
mode). We also provide a semi-generic fallback message for possible
future cases like this where an error is signalled, but no message is
sent to the client. The error/warning handling is unified so it's the
same again for variables provided by plugins and those in the server
proper.


mysql-test/r/plugin.result:
  show that on out-of-range values, plugin interface throws errors
  in STRICT mode and warnings otherwise.
mysql-test/t/plugin.test:
  show that on out-of-range values, plugin interface throws errors
  in STRICT mode and warnings otherwise.
sql/set_var.cc:
  - handle signedness of values used in warnings
  - in STRICT mode, throw errors rather than warnings
sql/sql_parse.cc:
  If sql_set_variables() returns with an error but no message
  was sent to the client, send a semi-generic one so the session
  won't hang and we won't fail silently.
sql/sql_plugin.cc:
  throw a warning if more than just block-size was corrected
  (or an error in STRICT mode). use functions from set_var
  for uniform behaviour of server- and plug-in variables.
storage/example/ha_example.cc:
  Add a ULONG system variable to example plugin so
  we can test integers in the plugin-interface without
  having to depend on the presence of innobase.

1 files changed, 14 insertions, 0 deletions

diff --git a/storage/example/ha_example.cc b/storage/example/ha_example.cc
index 6d9f4841e06..604722c3c8c 100644
--- a/storage/example/ha_example.cc
+++ b/storage/example/ha_example.cc
@@ -849,6 +849,7 @@ struct st_mysql_storage_engine example_storage_engine=
 { MYSQL_HANDLERTON_INTERFACE_VERSION };
 
 static ulong srv_enum_var= 0;
+static ulong srv_ulong_var= 0;
 
 const char *enum_var_names[]=
 {
@@ -871,8 +872,21 @@ static MYSQL_SYSVAR_ENUM(
   0,                              // def
   &enum_var_typelib);             // typelib
 
+static MYSQL_SYSVAR_ULONG(
+  ulong_var,
+  srv_ulong_var,
+  PLUGIN_VAR_RQCMDARG,
+  "0..1000",
+  NULL,
+  NULL,
+  8,
+  0,
+  1000,
+  0);
+
 static struct st_mysql_sys_var* example_system_variables[]= {
   MYSQL_SYSVAR(enum_var),
+  MYSQL_SYSVAR(ulong_var),
   NULL
 };